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separately
When watchdog_hardlockup_probe() is being called by
lockup_detector_delay_init(), an error return of -ENODEV will happen
for the arm64 arch when arch_perf_nmi_is_available() returns false. This
means that NMI is not usable by the hard lockup detector and so has to
be disabled. This can be considered a deficiency in that particular
arm64 chip, but there is nothing we can do about it. That also means
the following error will always be reported when the kernel boot up.
watchdog: Delayed init of the lockup detector failed: -19
The word "failed" itself has a connotation that there is something
wrong with the kernel which is not really the case here. Handle this
special ENODEV case separately and explain the reason behind disabling
hard lockup detector without causing anxiety for those users who read
the above message and wonder about it.
Link: https://lkml.kernel.org/r/20240802151621.617244-1-longman@redhat.com
Signed-off-by: Waiman Long <longman@redhat.com>
Cc: Douglas Anderson <dianders@chromium.org>
Cc: Joel Granados <j.granados@samsung.com>
Cc: Li Zhe <lizhe.67@bytedance.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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const qualify the struct ctl_table argument in the proc_handler function
signatures. This is a prerequisite to moving the static ctl_table
structs into .rodata data which will ensure that proc_handler function
pointers cannot be modified.
This patch has been generated by the following coccinelle script:
```
virtual patch
@r1@
identifier ctl, write, buffer, lenp, ppos;
identifier func !~ "appldata_(timer|interval)_handler|sched_(rt|rr)_handler|rds_tcp_skbuf_handler|proc_sctp_do_(hmac_alg|rto_min|rto_max|udp_port|alpha_beta|auth|probe_interval)";
@@
int func(
- struct ctl_table *ctl
+ const struct ctl_table *ctl
,int write, void *buffer, size_t *lenp, loff_t *ppos);
@r2@
identifier func, ctl, write, buffer, lenp, ppos;
@@
int func(
- struct ctl_table *ctl
+ const struct ctl_table *ctl
,int write, void *buffer, size_t *lenp, loff_t *ppos)
{ ... }
@r3@
identifier func;
@@
int func(
- struct ctl_table *
+ const struct ctl_table *
,int , void *, size_t *, loff_t *);
@r4@
identifier func, ctl;
@@
int func(
- struct ctl_table *ctl
+ const struct ctl_table *ctl
,int , void *, size_t *, loff_t *);
@r5@
identifier func, write, buffer, lenp, ppos;
@@
int func(
- struct ctl_table *
+ const struct ctl_table *
,int write, void *buffer, size_t *lenp, loff_t *ppos);
```
* Code formatting was adjusted in xfs_sysctl.c to comply with code
conventions. The xfs_stats_clear_proc_handler,
xfs_panic_mask_proc_handler and xfs_deprecated_dointvec_minmax where
adjusted.
* The ctl_table argument in proc_watchdog_common was const qualified.
This is called from a proc_handler itself and is calling back into
another proc_handler, making it necessary to change it as part of the
proc_handler migration.
Co-developed-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Co-developed-by: Joel Granados <j.granados@samsung.com>
Signed-off-by: Joel Granados <j.granados@samsung.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull non-mm updates from Andrew Morton:
"Mainly singleton patches, documented in their respective changelogs.
Notable series include:
- Some maintenance and performance work for ocfs2 in Heming Zhao's
series "improve write IO performance when fragmentation is high".
- Some ocfs2 bugfixes from Su Yue in the series "ocfs2 bugs fixes
exposed by fstests".
- kfifo header rework from Andy Shevchenko in the series "kfifo:
Clean up kfifo.h".
- GDB script fixes from Florian Rommel in the series "scripts/gdb:
Fixes for $lx_current and $lx_per_cpu".
- After much discussion, a coding-style update from Barry Song
explaining one reason why inline functions are preferred over
macros. The series is "codingstyle: avoid unused parameters for a
function-like macro""
* tag 'mm-nonmm-stable-2024-05-19-11-56' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (62 commits)
fs/proc: fix softlockup in __read_vmcore
nilfs2: convert BUG_ON() in nilfs_finish_roll_forward() to WARN_ON()
scripts: checkpatch: check unused parameters for function-like macro
Documentation: coding-style: ask function-like macros to evaluate parameters
nilfs2: use __field_struct() for a bitwise field
selftests/kcmp: remove unused open mode
nilfs2: remove calls to folio_set_error() and folio_clear_error()
kernel/watchdog_perf.c: tidy up kerneldoc
watchdog: allow nmi watchdog to use raw perf event
watchdog: handle comma separated nmi_watchdog command line
nilfs2: make superblock data array index computation sparse friendly
squashfs: remove calls to set the folio error flag
squashfs: convert squashfs_symlink_read_folio to use folio APIs
scripts/gdb: fix detection of current CPU in KGDB
scripts/gdb: make get_thread_info accept pointers
scripts/gdb: fix parameter handling in $lx_per_cpu
scripts/gdb: fix failing KGDB detection during probe
kfifo: don't use "proxy" headers
media: stih-cec: add missing io.h
media: rc: add missing io.h
...
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git://git.kernel.org/pub/scm/linux/kernel/git/sysctl/sysctl
Pull sysctl updates from Joel Granados:
- Remove sentinel elements from ctl_table structs in kernel/*
Removing sentinels in ctl_table arrays reduces the build time size
and runtime memory consumed by ~64 bytes per array. Removals for
net/, io_uring/, mm/, ipc/ and security/ are set to go into mainline
through their respective subsystems making the next release the most
likely place where the final series that removes the check for
proc_name == NULL will land.
This adds to removals already in arch/, drivers/ and fs/.
- Adjust ctl_table definitions and references to allow constification
- Remove unused ctl_table function arguments
- Move non-const elements from ctl_table to ctl_table_header
- Make ctl_table pointers const in ctl_table_root structure
Making the static ctl_table structs const will increase safety by
keeping the pointers to proc_handler functions in .rodata. Though no
ctl_tables where made const in this PR, the ground work for making
that possible has started with these changes sent by Thomas
Weißschuh.
* tag 'sysctl-6.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/sysctl/sysctl:
sysctl: drop now unnecessary out-of-bounds check
sysctl: move sysctl type to ctl_table_header
sysctl: drop sysctl_is_perm_empty_ctl_table
sysctl: treewide: constify argument ctl_table_root::permissions(table)
sysctl: treewide: drop unused argument ctl_table_root::set_ownership(table)
bpf: Remove the now superfluous sentinel elements from ctl_table array
delayacct: Remove the now superfluous sentinel elements from ctl_table array
kprobes: Remove the now superfluous sentinel elements from ctl_table array
printk: Remove the now superfluous sentinel elements from ctl_table array
scheduler: Remove the now superfluous sentinel elements from ctl_table array
seccomp: Remove the now superfluous sentinel elements from ctl_table array
timekeeping: Remove the now superfluous sentinel elements from ctl_table array
ftrace: Remove the now superfluous sentinel elements from ctl_table array
umh: Remove the now superfluous sentinel elements from ctl_table array
kernel misc: Remove the now superfluous sentinel elements from ctl_table array
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NMI watchdog permanently consumes one hardware counters per CPU on the
system. For systems that use many hardware counters, this causes more
aggressive time multiplexing of perf events.
OTOH, some CPUs (mostly Intel) support "ref-cycles" event, which is rarely
used. Add kernel cmdline arg nmi_watchdog=rNNN to configure the watchdog
to use raw event. For example, on Intel CPUs, we can use "r300" to
configure the watchdog to use ref-cycles event.
If the raw event does not work, fall back to use "cycles".
[akpm@linux-foundation.org: fix kerneldoc]
Link: https://lkml.kernel.org/r/20240430060236.1878002-2-song@kernel.org
Signed-off-by: Song Liu <song@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Per the document, the kernel can accept comma separated command line like
nmi_watchdog=nopanic,0. However, the code doesn't really handle it. Fix
the kernel to handle it properly.
Link: https://lkml.kernel.org/r/20240430060236.1878002-1-song@kernel.org
Signed-off-by: Song Liu <song@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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This commit comes at the tail end of a greater effort to remove the
empty elements at the end of the ctl_table arrays (sentinels) which
will reduce the overall build time size of the kernel and run time
memory bloat by ~64 bytes per sentinel (further information Link :
https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/)
Remove the sentinel from ctl_table arrays. Reduce by one the values used
to compare the size of the adjusted arrays.
Signed-off-by: Joel Granados <j.granados@samsung.com>
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When the watchdog determines that the current soft lockup is due to an
interrupt storm based on CPU utilization, reporting the most frequent
interrupts could be good enough for further troubleshooting.
Below is an example of interrupt storm. The call tree does not provide
useful information, but analyzing which interrupt caused the soft lockup by
comparing the counts of interrupts during the lockup period allows to
identify the culprit.
[ 638.870231] watchdog: BUG: soft lockup - CPU#9 stuck for 26s! [swapper/9:0]
[ 638.870825] CPU#9 Utilization every 4s during lockup:
[ 638.871194] #1: 0% system, 0% softirq, 100% hardirq, 0% idle
[ 638.871652] #2: 0% system, 0% softirq, 100% hardirq, 0% idle
[ 638.872107] #3: 0% system, 0% softirq, 100% hardirq, 0% idle
[ 638.872563] #4: 0% system, 0% softirq, 100% hardirq, 0% idle
[ 638.873018] #5: 0% system, 0% softirq, 100% hardirq, 0% idle
[ 638.873494] CPU#9 Detect HardIRQ Time exceeds 50%. Most frequent HardIRQs:
[ 638.873994] #1: 330945 irq#7
[ 638.874236] #2: 31 irq#82
[ 638.874493] #3: 10 irq#10
[ 638.874744] #4: 2 irq#89
[ 638.874992] #5: 1 irq#102
...
[ 638.875313] Call trace:
[ 638.875315] __do_softirq+0xa8/0x364
Signed-off-by: Bitao Hu <yaoma@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Liu Song <liusong@linux.alibaba.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20240411074134.30922-6-yaoma@linux.alibaba.com
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The following softlockup is caused by interrupt storm, but it cannot be
identified from the call tree. Because the call tree is just a snapshot
and doesn't fully capture the behavior of the CPU during the soft lockup.
watchdog: BUG: soft lockup - CPU#28 stuck for 23s! [fio:83921]
...
Call trace:
__do_softirq+0xa0/0x37c
__irq_exit_rcu+0x108/0x140
irq_exit+0x14/0x20
__handle_domain_irq+0x84/0xe0
gic_handle_irq+0x80/0x108
el0_irq_naked+0x50/0x58
Therefore, it is necessary to report CPU utilization during the
softlockup_threshold period (report once every sample_period, for a total
of 5 reportings), like this:
watchdog: BUG: soft lockup - CPU#28 stuck for 23s! [fio:83921]
CPU#28 Utilization every 4s during lockup:
#1: 0% system, 0% softirq, 100% hardirq, 0% idle
#2: 0% system, 0% softirq, 100% hardirq, 0% idle
#3: 0% system, 0% softirq, 100% hardirq, 0% idle
#4: 0% system, 0% softirq, 100% hardirq, 0% idle
#5: 0% system, 0% softirq, 100% hardirq, 0% idle
...
This is helpful in determining whether an interrupt storm has occurred or
in identifying the cause of the softlockup. The criteria for determination
are as follows:
a. If the hardirq utilization is high, then interrupt storm should be
considered and the root cause cannot be determined from the call tree.
b. If the softirq utilization is high, then the call might not necessarily
point at the root cause.
c. If the system utilization is high, then analyzing the root
cause from the call tree is possible in most cases.
The mechanism requires a considerable amount of global storage space
when configured for the maximum number of CPUs. Therefore, adding a
SOFTLOCKUP_DETECTOR_INTR_STORM Kconfig knob that defaults to "yes"
if the max number of CPUs is <= 128.
Signed-off-by: Bitao Hu <yaoma@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Liu Song <liusong@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240411074134.30922-5-yaoma@linux.alibaba.com
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The functions are only used in the file where they are defined. Remove
them from the header and make them static.
Also guard proc_soft_watchdog with a #define-guard as it is not used
otherwise.
Link: https://lkml.kernel.org/r/20240306-const-sysctl-prep-watchdog-v1-1-bd45da3a41cf@weissschuh.net
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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If, as part of handling a hardlockup or softlockup, we've already dumped
all CPUs and we're just about to panic, don't reenable dumping and give
some other CPU a chance to hop in there and add some confusing logs right
as the panic is happening.
Link: https://lkml.kernel.org/r/20231220131534.4.Id3a9c7ec2d7d83e4080da6f8662ba2226b40543f@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Li Zhe <lizhe.67@bytedance.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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If two CPUs end up reporting a hardlockup at the same time then their logs
could get interleaved which is hard to read.
The interleaving problem was especially bad with the "perf" hardlockup
detector where the locked up CPU is always the same as the running CPU and
we end up in show_regs(). show_regs() has no inherent serialization so we
could mix together two crawls if two hardlockups happened at the same time
(and if we didn't have `sysctl_hardlockup_all_cpu_backtrace` set). With
this change we'll fully serialize hardlockups when using the "perf"
hardlockup detector.
The interleaving problem was less bad with the "buddy" hardlockup
detector. With "buddy" we always end up calling
`trigger_single_cpu_backtrace(cpu)` on some CPU other than the running
one. trigger_single_cpu_backtrace() always at least serializes the
individual stack crawls because it eventually uses
printk_cpu_sync_get_irqsave(). Unfortunately the fact that
trigger_single_cpu_backtrace() eventually calls
printk_cpu_sync_get_irqsave() (on a different CPU) means that we have to
drop the "lock" before calling it and we can't fully serialize all
printouts associated with a given hardlockup. However, we still do get
the advantage of serializing the output of print_modules() and
print_irqtrace_events().
Aside from serializing hardlockups from each other, this change also has
the advantage of serializing hardlockups and softlockups from each other
if they happen to happen at the same time since they are both using the
same "lock".
Even though nobody is expected to hang while holding the lock associated
with printk_cpu_sync_get_irqsave(), out of an abundance of caution, we
don't call printk_cpu_sync_get_irqsave() until after we print out about
the hardlockup. This makes extra sure that, even if
printk_cpu_sync_get_irqsave() somehow never runs we at least print that we
saw the hardlockup. This is different than the choice made for softlockup
because hardlockup is really our last resort.
Link: https://lkml.kernel.org/r/20231220131534.3.I6ff691b3b40f0379bc860f80c6e729a0485b5247@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Li Zhe <lizhe.67@bytedance.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Instead of introducing a spinlock, use printk_cpu_sync_get_irqsave() and
printk_cpu_sync_put_irqrestore() to serialize softlockup reporting. Alone
this doesn't have any real advantage over the spinlock, but this will
allow us to use the same function in a future change to also serialize
hardlockup crawls.
NOTE: for the most part this serialization is important because we often
end up in the show_regs() path and that has no built-in serialization if
there are multiple callers at once. However, even in the case where we
end up in the dump_stack() path this still has some advantages because the
stack will be guaranteed to be together in the logs with the lockup
message with no interleaving.
NOTE: the fact that printk_cpu_sync_get_irqsave() is allowed to be called
multiple times on the same CPU is important here. Specifically we hold
the "lock" while calling dump_stack() which also gets the same "lock".
This is explicitly documented to be OK and means we don't need to
introduce a variant of dump_stack() that doesn't grab the lock.
Link: https://lkml.kernel.org/r/20231220131534.2.Ia5906525d440d8e8383cde31b7c61c2aadc8f907@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Li Zhe <lizhe.67@bytedance.com>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Patch series "watchdog: Better handling of concurrent lockups".
When we get multiple lockups at roughly the same time, the output in the
kernel logs can be very confusing since the reports about the lockups end
up interleaved in the logs. There is some code in the kernel to try to
handle this but it wasn't that complete.
Li Zhe recently made this a bit better for softlockups (specifically for
the case where `kernel.softlockup_all_cpu_backtrace` is not set) in commit
9d02330abd3e ("softlockup: serialized softlockup's log"), but that only
handled softlockup reports. Hardlockup reports still had similar issues.
This series also has a small fix to avoid dumping all stacks a second time
in the case of a panic. This is a bit unrelated to the interleaving fixes
but it does also improve the clarity of lockup reports.
This patch (of 4):
The hardlockup detector and softlockup detector both have the ability to
dump the stack of all CPUs (`kernel.hardlockup_all_cpu_backtrace` and
`kernel.softlockup_all_cpu_backtrace`). Both detectors also have some
logic to attempt to avoid interleaving printouts if two CPUs were trying
to do dumps of all CPUs at the same time. However:
- The hardlockup detector's logic still allowed interleaving some
information. Specifically another CPU could print modules and dump
the stack of the locked CPU at the same time we were dumping all
CPUs.
- In the case where `kernel.hardlockup_panic` was set in addition to
`kernel.hardlockup_all_cpu_backtrace`, when two CPUs both detected
hardlockups at the same time the second CPU could call panic() while
the first was still dumping stacks. This was especially bad if the
locked up CPU wasn't responding to the request for a backtrace since
the function nmi_trigger_cpumask_backtrace() can wait up to 10
seconds.
Let's resolve this by adopting the softlockup logic in the hardlockup
handler.
NOTES:
- As part of this, one might think that we should make a helper
function that both the hard and softlockup detectors call. This
turns out not to be super trivial since it would have to be
parameterized quite a bit since there are separate global variables
controlling each lockup detector and they print log messages that
are just different enough that it would be a pain. We probably don't
want to change the messages that are printed without good reason to
avoid throwing log parsers for a loop.
- One might also think that it would be a good idea to have the
hardlockup and softlockup detector use the same global variable to
prevent interleaving. This would make sure that softlockups and
hardlockups can't interleave each other. That _almost_ works but has
a dangerous flaw if `kernel.hardlockup_panic` is not the same as
`kernel.softlockup_panic` because we might skip a call to panic() if
one type of lockup was detected at the same time as another.
Link: https://lkml.kernel.org/r/20231220211640.2023645-1-dianders@chromium.org
Link: https://lkml.kernel.org/r/20231220131534.1.I4f35a69fbb124b5f0c71f75c631e11fabbe188ff@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Li Zhe <lizhe.67@bytedance.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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If multiple CPUs trigger softlockup at the same time with
'softlockup_all_cpu_backtrace=0', the softlockup's logs will appear
staggeredly in dmesg, which will affect the viewing of the logs for
developer. Since the code path for outputting softlockup logs is not a
kernel hotspot and the performance requirements for the code are not
strict, locks are used to serialize the softlockup log output to improve
the readability of the logs.
Link: https://lkml.kernel.org/r/20231123084022.10302-1-lizhe.67@bytedance.com
Signed-off-by: Li Zhe <lizhe.67@bytedance.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Cc: Zefan Li <lizefan.x@bytedance.com>
Cc: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Setting softlockup_panic from do_sysctl_args() causes it to take effect
later in boot. The lockup detector is enabled before SMP is brought
online, but do_sysctl_args runs afterwards. If a user wants to set
softlockup_panic on boot and have it trigger should a softlockup occur
during onlining of the non-boot processors, they could do this prior to
commit f117955a2255 ("kernel/watchdog.c: convert {soft/hard}lockup boot
parameters to sysctl aliases"). However, after this commit the value
of softlockup_panic is set too late to be of help for this type of
problem. Restore the prior behavior.
Signed-off-by: Krister Johansen <kjlx@templeofstupid.com>
Cc: stable@vger.kernel.org
Fixes: f117955a2255 ("kernel/watchdog.c: convert {soft/hard}lockup boot parameters to sysctl aliases")
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
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After commit 77c12fc95980 ("watchdog/hardlockup: add a "cpu" param to
watchdog_hardlockup_check()") we started storing a `struct cpumask` on the
stack in watchdog_hardlockup_check(). On systems with CONFIG_NR_CPUS set
to 8192 this takes up 1K on the stack. That triggers warnings with
`CONFIG_FRAME_WARN` set to 1024.
We'll use the new trigger_allbutcpu_cpu_backtrace() to avoid needing to
use a CPU mask at all.
Link: https://lkml.kernel.org/r/20230804065935.v4.2.I501ab68cb926ee33a7c87e063d207abf09b9943c@changeid
Fixes: 77c12fc95980 ("watchdog/hardlockup: add a "cpu" param to watchdog_hardlockup_check()")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/r/202307310955.pLZDhpnl-lkp@intel.com
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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The APIs that allow backtracing across CPUs have always had a way to
exclude the current CPU. This convenience means callers didn't need to
find a place to allocate a CPU mask just to handle the common case.
Let's extend the API to take a CPU ID to exclude instead of just a
boolean. This isn't any more complex for the API to handle and allows the
hardlockup detector to exclude a different CPU (the one it already did a
trace for) without needing to find space for a CPU mask.
Arguably, this new API also encourages safer behavior. Specifically if
the caller wants to avoid tracing the current CPU (maybe because they
already traced the current CPU) this makes it more obvious to the caller
that they need to make sure that the current CPU ID can't change.
[akpm@linux-foundation.org: fix trigger_allbutcpu_cpu_backtrace() stub]
Link: https://lkml.kernel.org/r/20230804065935.v4.1.Ia35521b91fc781368945161d7b28538f9996c182@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: kernel test robot <lkp@intel.com>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
The HAVE_ prefix means that the code could be enabled. Add another
variable for HAVE_HARDLOCKUP_DETECTOR_SPARC64 without this prefix.
It will be set when it should be built. It will make it compatible
with the other hardlockup detectors.
Before, it is far from obvious that the SPARC64 variant is actually used:
$> make ARCH=sparc64 defconfig
$> grep HARDLOCKUP_DETECTOR .config
CONFIG_HAVE_HARDLOCKUP_DETECTOR_BUDDY=y
CONFIG_HAVE_HARDLOCKUP_DETECTOR_SPARC64=y
After, it is more clear:
$> make ARCH=sparc64 defconfig
$> grep HARDLOCKUP_DETECTOR .config
CONFIG_HAVE_HARDLOCKUP_DETECTOR_BUDDY=y
CONFIG_HAVE_HARDLOCKUP_DETECTOR_SPARC64=y
CONFIG_HARDLOCKUP_DETECTOR_SPARC64=y
Link: https://lkml.kernel.org/r/20230616150618.6073-6-pmladek@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
There are several hardlockup detector implementations and several Kconfig
values which allow selection and build of the preferred one.
CONFIG_HARDLOCKUP_DETECTOR was introduced by the commit 23637d477c1f53acb
("lockup_detector: Introduce CONFIG_HARDLOCKUP_DETECTOR") in v2.6.36.
It was a preparation step for introducing the new generic perf hardlockup
detector.
The existing arch-specific variants did not support the to-be-created
generic build configurations, sysctl interface, etc. This distinction
was made explicit by the commit 4a7863cc2eb5f98 ("x86, nmi_watchdog:
Remove ARCH_HAS_NMI_WATCHDOG and rely on CONFIG_HARDLOCKUP_DETECTOR")
in v2.6.38.
CONFIG_HAVE_NMI_WATCHDOG was introduced by the commit d314d74c695f967e105
("nmi watchdog: do not use cpp symbol in Kconfig") in v3.4-rc1. It replaced
the above mentioned ARCH_HAS_NMI_WATCHDOG. At that time, it was still used
by three architectures, namely blackfin, mn10300, and sparc.
The support for blackfin and mn10300 architectures has been completely
dropped some time ago. And sparc is the only architecture with the historic
NMI watchdog at the moment.
And the old sparc implementation is really special. It is always built on
sparc64. It used to be always enabled until the commit 7a5c8b57cec93196b
("sparc: implement watchdog_nmi_enable and watchdog_nmi_disable") added
in v4.10-rc1.
There are only few locations where the sparc64 NMI watchdog interacts
with the generic hardlockup detectors code:
+ implements arch_touch_nmi_watchdog() which is called from the generic
touch_nmi_watchdog()
+ implements watchdog_hardlockup_enable()/disable() to support
/proc/sys/kernel/nmi_watchdog
+ is always preferred over other generic watchdogs, see
CONFIG_HARDLOCKUP_DETECTOR
+ includes asm/nmi.h into linux/nmi.h because some sparc-specific
functions are needed in sparc-specific code which includes
only linux/nmi.h.
The situation became more complicated after the commit 05a4a95279311c3
("kernel/watchdog: split up config options") and commit 2104180a53698df5
("powerpc/64s: implement arch-specific hardlockup watchdog") in v4.13-rc1.
They introduced HAVE_HARDLOCKUP_DETECTOR_ARCH. It was used for powerpc
specific hardlockup detector. It was compatible with the perf one
regarding the general boot, sysctl, and programming interfaces.
HAVE_HARDLOCKUP_DETECTOR_ARCH was defined as a superset of
HAVE_NMI_WATCHDOG. It made some sense because all arch-specific
detectors had some common requirements, namely:
+ implemented arch_touch_nmi_watchdog()
+ included asm/nmi.h into linux/nmi.h
+ defined the default value for /proc/sys/kernel/nmi_watchdog
But it actually has made things pretty complicated when the generic
buddy hardlockup detector was added. Before the generic perf detector
was newer supported together with an arch-specific one. But the buddy
detector could work on any SMP system. It means that an architecture
could support both the arch-specific and buddy detector.
As a result, there are few tricky dependencies. For example,
CONFIG_HARDLOCKUP_DETECTOR depends on:
((HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_BUDDY) && !HAVE_NMI_WATCHDOG) || HAVE_HARDLOCKUP_DETECTOR_ARCH
The problem is that the very special sparc implementation is defined as:
HAVE_NMI_WATCHDOG && !HAVE_HARDLOCKUP_DETECTOR_ARCH
Another problem is that the meaning of HAVE_NMI_WATCHDOG is far from clear
without reading understanding the history.
Make the logic less tricky and more self-explanatory by making
HAVE_NMI_WATCHDOG specific for the sparc64 implementation. And rename it to
HAVE_HARDLOCKUP_DETECTOR_SPARC64.
Note that HARDLOCKUP_DETECTOR_PREFER_BUDDY, HARDLOCKUP_DETECTOR_PERF,
and HARDLOCKUP_DETECTOR_BUDDY may conflict only with
HAVE_HARDLOCKUP_DETECTOR_ARCH. They depend on HARDLOCKUP_DETECTOR
and it is not longer enabled when HAVE_NMI_WATCHDOG is set.
Link: https://lkml.kernel.org/r/20230616150618.6073-5-pmladek@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
It's been suggested that since the SMP barriers are only potentially
useful for the buddy hardlockup detector, not the perf hardlockup
detector, that the barriers belong in the buddy code. Let's move them and
add clearer comments about why they're needed.
Link: https://lkml.kernel.org/r/20230526184139.9.I5ab0a0eeb0bd52fb23f901d298c72fa5c396e22b@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Suggested-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
In the patch ("watchdog/hardlockup: detect hard lockups using secondary
(buddy) CPUs"), we added a call from the common watchdog.c file into the
buddy. That call could be done more cleanly. Specifically:
1. If we move the call into watchdog_hardlockup_kick() then it keeps
watchdog_timer_fn() simpler.
2. We don't need to pass an "unsigned long" to the buddy for the timer
count. In the patch ("watchdog/hardlockup: add a "cpu" param to
watchdog_hardlockup_check()") the count was changed to "atomic_t"
which is backed by an int, so we should match types.
Link: https://lkml.kernel.org/r/20230526184139.6.I006c7d958a1ea5c4e1e4dc44a25596d9bb5fd3ba@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Suggested-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
In the patch ("watchdog/hardlockup: add a "cpu" param to
watchdog_hardlockup_check()") we started using a cpumask to keep track of
which CPUs to backtrace. When setting up this cpumask, it's better to use
cpumask_copy() than to just copy the structure directly. Fix this.
Link: https://lkml.kernel.org/r/20230526184139.4.Iccee2d1ea19114dafb6553a854ea4d8ab2a3f25b@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Suggested-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
In the patch ("watchdog/hardlockup: add a "cpu" param to
watchdog_hardlockup_check()") there was no reason to use raw_cpu_ptr().
Using this_cpu_ptr() works fine.
Link: https://lkml.kernel.org/r/20230526184139.3.I660e103077dcc23bb29aaf2be09cb234e0495b2d@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Suggested-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
watchdog_hardlockup_probe()
Right now there is one arch (sparc64) that selects HAVE_NMI_WATCHDOG
without selecting HAVE_HARDLOCKUP_DETECTOR_ARCH. Because of that one
architecture, we have some special case code in the watchdog core to
handle the fact that watchdog_hardlockup_probe() isn't implemented.
Let's implement watchdog_hardlockup_probe() for sparc64 and get rid of the
special case.
As a side effect of doing this, code inspection tells us that we could fix
a minor bug where the system won't properly realize that NMI watchdogs are
disabled. Specifically, on powerpc if CONFIG_PPC_WATCHDOG is turned off
the arch might still select CONFIG_HAVE_HARDLOCKUP_DETECTOR_ARCH which
selects CONFIG_HAVE_NMI_WATCHDOG. Since CONFIG_PPC_WATCHDOG was off then
nothing will override the "weak" watchdog_hardlockup_probe() and we'll
fallback to looking at CONFIG_HAVE_NMI_WATCHDOG.
Link: https://lkml.kernel.org/r/20230526184139.2.Ic6ebbf307ca0efe91f08ce2c1eb4a037ba6b0700@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Suggested-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Patch series "watchdog: Cleanup / fixes after buddy series v5 reviews".
This patch series attempts to finish resolving the feedback received
from Petr Mladek on the v5 series I posted.
Probably the only thing that wasn't fully as clean as Petr requested was
the Kconfig stuff. I couldn't find a better way to express it without a
more major overhaul. In the very least, I renamed "NON_ARCH" to
"PERF_OR_BUDDY" in the hopes that will make it marginally better.
Nothing in this series is terribly critical and even the bugfixes are
small. However, it does cleanup a few things that were pointed out in
review.
This patch (of 10):
The permissions for the kernel.nmi_watchdog sysctl have always been set at
compile time despite the fact that a watchdog can fail to probe. Let's
fix this and set the permissions based on whether the hardlockup detector
actually probed.
Link: https://lkml.kernel.org/r/20230527014153.2793931-1-dianders@chromium.org
Link: https://lkml.kernel.org/r/20230526184139.1.I0d75971cc52a7283f495aac0bd5c3041aadc734e@changeid
Fixes: a994a3147e4c ("watchdog/hardlockup/perf: Implement init time detection of perf")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reported-by: Petr Mladek <pmladek@suse.com>
Closes: https://lore.kernel.org/r/ZHCn4hNxFpY5-9Ki@alley
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
When lockup_detector_init()->watchdog_hardlockup_probe(), PMU may be not
ready yet. E.g. on arm64, PMU is not ready until
device_initcall(armv8_pmu_driver_init). And it is deeply integrated with
the driver model and cpuhp. Hence it is hard to push this initialization
before smp_init().
But it is easy to take an opposite approach and try to initialize the
watchdog once again later. The delayed probe is called using workqueues.
It need to allocate memory and must be proceed in a normal context. The
delayed probe is able to use if watchdog_hardlockup_probe() returns
non-zero which means the return code returned when PMU is not ready yet.
Provide an API - lockup_detector_retry_init() for anyone who needs to
delayed init lockup detector if they had ever failed at
lockup_detector_init().
The original assumption is: nobody should use delayed probe after
lockup_detector_check() which has __init attribute. That is, anyone uses
this API must call between lockup_detector_init() and
lockup_detector_check(), and the caller must have __init attribute
Link: https://lkml.kernel.org/r/20230519101840.v5.16.If4ad5dd5d09fb1309cebf8bcead4b6a5a7758ca7@changeid
Reviewed-by: Petr Mladek <pmladek@suse.com>
Co-developed-by: Pingfan Liu <kernelfans@gmail.com>
Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Suggested-by: Petr Mladek <pmladek@suse.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Colin Cross <ccross@android.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Sumit Garg <sumit.garg@linaro.org>
Cc: Tzung-Bi Shih <tzungbi@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Implement a hardlockup detector that doesn't doesn't need any extra
arch-specific support code to detect lockups. Instead of using something
arch-specific we will use the buddy system, where each CPU watches out for
another one. Specifically, each CPU will use its softlockup hrtimer to
check that the next CPU is processing hrtimer interrupts by verifying that
a counter is increasing.
NOTE: unlike the other hard lockup detectors, the buddy one can't easily
show what's happening on the CPU that locked up just by doing a simple
backtrace. It relies on some other mechanism in the system to get
information about the locked up CPUs. This could be support for NMI
backtraces like [1], it could be a mechanism for printing the PC of locked
CPUs at panic time like [2] / [3], or it could be something else. Even
though that means we still rely on arch-specific code, this arch-specific
code seems to often be implemented even on architectures that don't have a
hardlockup detector.
This style of hardlockup detector originated in some downstream Android
trees and has been rebased on / carried in ChromeOS trees for quite a long
time for use on arm and arm64 boards. Historically on these boards we've
leveraged mechanism [2] / [3] to get information about hung CPUs, but we
could move to [1].
Although the original motivation for the buddy system was for use on
systems without an arch-specific hardlockup detector, it can still be
useful to use even on systems that _do_ have an arch-specific hardlockup
detector. On x86, for instance, there is a 24-part patch series [4] in
progress switching the arch-specific hard lockup detector from a scarce
perf counter to a less-scarce hardware resource. Potentially the buddy
system could be a simpler alternative to free up the perf counter but
still get hard lockup detection.
Overall, pros (+) and cons (-) of the buddy system compared to an
arch-specific hardlockup detector (which might be implemented using
perf):
+ The buddy system is usable on systems that don't have an
arch-specific hardlockup detector, like arm32 and arm64 (though it's
being worked on for arm64 [5]).
+ The buddy system may free up scarce hardware resources.
+ If a CPU totally goes out to lunch (can't process NMIs) the buddy
system could still detect the problem (though it would be unlikely
to be able to get a stack trace).
+ The buddy system uses the same timer function to pet the hardlockup
detector on the running CPU as it uses to detect hardlockups on
other CPUs. Compared to other hardlockup detectors, this means it
generates fewer interrupts and thus is likely better able to let
CPUs stay idle longer.
- If all CPUs are hard locked up at the same time the buddy system
can't detect it.
- If we don't have SMP we can't use the buddy system.
- The buddy system needs an arch-specific mechanism (possibly NMI
backtrace) to get info about the locked up CPU.
[1] https://lore.kernel.org/r/20230419225604.21204-1-dianders@chromium.org
[2] https://issuetracker.google.com/172213129
[3] https://docs.kernel.org/trace/coresight/coresight-cpu-debug.html
[4] https://lore.kernel.org/lkml/20230301234753.28582-1-ricardo.neri-calderon@linux.intel.com/
[5] https://lore.kernel.org/linux-arm-kernel/20220903093415.15850-1-lecopzer.chen@mediatek.com/
Link: https://lkml.kernel.org/r/20230519101840.v5.14.I6bf789d21d0c3d75d382e7e51a804a7a51315f2c@changeid
Signed-off-by: Colin Cross <ccross@android.com>
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Tzung-Bi Shih <tzungbi@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Ian Rogers <irogers@google.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Sumit Garg <sumit.garg@linaro.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
The fact that there watchdog_hardlockup_enable(),
watchdog_hardlockup_disable(), and watchdog_hardlockup_probe() are
declared __weak means that the configured hardlockup detector can define
non-weak versions of those functions if it needs to. Instead of doing
this, the perf hardlockup detector hooked itself into the default __weak
implementation, which was a bit awkward. Clean this up.
From comments, it looks as if the original design was done because the
__weak function were expected to implemented by the architecture and not
by the configured hardlockup detector. This got awkward when we tried to
add the buddy lockup detector which was not arch-specific but wanted to
hook into those same functions.
This is not expected to have any functional impact.
Link: https://lkml.kernel.org/r/20230519101840.v5.13.I847d9ec852449350997ba00401d2462a9cb4302b@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Colin Cross <ccross@android.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Sumit Garg <sumit.garg@linaro.org>
Cc: Tzung-Bi Shih <tzungbi@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Do a search and replace of:
- NMI_WATCHDOG_ENABLED => WATCHDOG_HARDLOCKUP_ENABLED
- SOFT_WATCHDOG_ENABLED => WATCHDOG_SOFTOCKUP_ENABLED
- watchdog_nmi_ => watchdog_hardlockup_
- nmi_watchdog_available => watchdog_hardlockup_available
- nmi_watchdog_user_enabled => watchdog_hardlockup_user_enabled
- soft_watchdog_user_enabled => watchdog_softlockup_user_enabled
- NMI_WATCHDOG_DEFAULT => WATCHDOG_HARDLOCKUP_DEFAULT
Then update a few comments near where names were changed.
This is specifically to make it less confusing when we want to introduce
the buddy hardlockup detector, which isn't using NMIs. As part of this,
we sanitized a few names for consistency.
[trix@redhat.com: make variables static]
Link: https://lkml.kernel.org/r/20230525162822.1.I0fb41d138d158c9230573eaa37dc56afa2fb14ee@changeid
Link: https://lkml.kernel.org/r/20230519101840.v5.12.I91f7277bab4bf8c0cb238732ed92e7ce7bbd71a6@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: Tom Rix <trix@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Colin Cross <ccross@android.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Sumit Garg <sumit.garg@linaro.org>
Cc: Tzung-Bi Shih <tzungbi@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
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In preparation for the buddy hardlockup detector, which wants the same
petting logic as the current perf hardlockup detector, move the code to
watchdog.c. While doing this, rename the global variable to match others
nearby. As part of this change we have to change the code to account for
the fact that the CPU we're running on might be different than the one
we're checking.
Currently the code in watchdog.c is guarded by
CONFIG_HARDLOCKUP_DETECTOR_PERF, which makes this change seem silly.
However, a future patch will change this.
Link: https://lkml.kernel.org/r/20230519101840.v5.11.I00dfd6386ee00da25bf26d140559a41339b53e57@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Colin Cross <ccross@android.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Sumit Garg <sumit.garg@linaro.org>
Cc: Tzung-Bi Shih <tzungbi@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
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In preparation for the buddy hardlockup detector where the CPU checking
for lockup might not be the currently running CPU, add a "cpu" parameter
to watchdog_hardlockup_check().
As part of this change, make hrtimer_interrupts an atomic_t since now the
CPU incrementing the value and the CPU reading the value might be
different. Technially this could also be done with just READ_ONCE and
WRITE_ONCE, but atomic_t feels a little cleaner in this case.
While hrtimer_interrupts is made atomic_t, we change
hrtimer_interrupts_saved from "unsigned long" to "int". The "int" is
needed to match the data type backing atomic_t for hrtimer_interrupts.
Even if this changes us from 64-bits to 32-bits (which I don't think is
true for most compilers), it doesn't really matter. All we ever do is
increment it every few seconds and compare it to an old value so 32-bits
is fine (even 16-bits would be). The "signed" vs "unsigned" also doesn't
matter for simple equality comparisons.
hrtimer_interrupts_saved is _not_ switched to atomic_t nor even accessed
with READ_ONCE / WRITE_ONCE. The hrtimer_interrupts_saved is always
consistently accessed with the same CPU. NOTE: with the upcoming "buddy"
detector there is one special case. When a CPU goes offline/online then
we can change which CPU is the one to consistently access a given instance
of hrtimer_interrupts_saved. We still can't end up with a partially
updated hrtimer_interrupts_saved, however, because we end up petting all
affected CPUs to make sure the new and old CPU can't end up somehow
read/write hrtimer_interrupts_saved at the same time.
Link: https://lkml.kernel.org/r/20230519101840.v5.10.I3a7d4dd8c23ac30ee0b607d77feb6646b64825c0@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Colin Cross <ccross@android.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Sumit Garg <sumit.garg@linaro.org>
Cc: Tzung-Bi Shih <tzungbi@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
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is_hardlockup()
These are tiny style changes:
- Add a blank line before a "return".
- Renames two globals to use the "watchdog_hardlockup" prefix.
- Store processor id in "unsigned int" rather than "int".
- Minor comment rewording.
- Use "else" rather than extra returns since it seemed more symmetric.
Link: https://lkml.kernel.org/r/20230519101840.v5.9.I818492c326b632560b09f20d2608455ecf9d3650@changeid
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Colin Cross <ccross@android.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Sumit Garg <sumit.garg@linaro.org>
Cc: Tzung-Bi Shih <tzungbi@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
The perf hardlockup detector works by looking at interrupt counts and
seeing if they change from run to run. The interrupt counts are managed
by the common watchdog code via its watchdog_timer_fn().
Currently the API between the perf detector and the common code is a
function: is_hardlockup(). When the hard lockup detector sees that
function return true then it handles printing out debug info and inducing
a panic if necessary.
Let's change the API a little bit in preparation for the buddy hardlockup
detector. The buddy hardlockup detector wants to print nearly the same
debug info and have nearly the same panic behavior. That means we want to
move all that code to the common file. For now, the code in the common
file will only be there if the perf hardlockup detector is enabled, but
eventually it will be selected by a common config.
Right now, this _just_ moves the code from the perf detector file to the
common file and changes the names. It doesn't make the changes that the
buddy hardlockup detector will need and doesn't do any style cleanups. A
future patch will do cleanup to make it more obvious what changed.
With the above, we no longer have any callers of is_hardlockup() outside
of the "watchdog.c" file, so we can remove it from the header, make it
static, and move it to the same "#ifdef" block as our new
watchdog_hardlockup_check(). While doing this, it can be noted that even
if no hardlockup detectors were configured the existing code used to still
have the code for counting/checking "hrtimer_interrupts" even if the perf
hardlockup detector wasn't configured. We didn't need to do that, so move
all the "hrtimer_interrupts" counting to only be there if the perf
hardlockup detector is configured as well.
This change is expected to be a no-op.
Link: https://lkml.kernel.org/r/20230519101840.v5.8.Id4133d3183e798122dc3b6205e7852601f289071@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Colin Cross <ccross@android.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Sumit Garg <sumit.garg@linaro.org>
Cc: Tzung-Bi Shih <tzungbi@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Nobody cares about the return value of watchdog_nmi_enable(), changing its
prototype to void.
Link: https://lkml.kernel.org/r/20230519101840.v5.4.Ic3a19b592eb1ac4c6f6eade44ffd943e8637b6e5@changeid
Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Nicholas Piggin <npiggin@gmail.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Colin Cross <ccross@android.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Sumit Garg <sumit.garg@linaro.org>
Cc: Tzung-Bi Shih <tzungbi@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
No reference to WATCHDOG_DEFAULT, remove it.
Link: https://lkml.kernel.org/r/20230519101840.v5.3.I6a729209a1320e0ad212176e250ff945b8f91b2a@changeid
Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Colin Cross <ccross@android.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Sumit Garg <sumit.garg@linaro.org>
Cc: Tzung-Bi Shih <tzungbi@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux
Pull powerpc updates from Michael Ellerman:
- Add support for syscall stack randomization
- Add support for atomic operations to the 32 & 64-bit BPF JIT
- Full support for KASAN on 64-bit Book3E
- Add a watchdog driver for the new PowerVM hypervisor watchdog
- Add a number of new selftests for the Power10 PMU support
- Add a driver for the PowerVM Platform KeyStore
- Increase the NMI watchdog timeout during live partition migration, to
avoid timeouts due to increased memory access latency
- Add support for using the 'linux,pci-domain' device tree property for
PCI domain assignment
- Many other small features and fixes
Thanks to Alexey Kardashevskiy, Andy Shevchenko, Arnd Bergmann, Athira
Rajeev, Bagas Sanjaya, Christophe Leroy, Erhard Furtner, Fabiano Rosas,
Greg Kroah-Hartman, Greg Kurz, Haowen Bai, Hari Bathini, Jason A.
Donenfeld, Jason Wang, Jiang Jian, Joel Stanley, Juerg Haefliger, Kajol
Jain, Kees Cook, Laurent Dufour, Madhavan Srinivasan, Masahiro Yamada,
Maxime Bizon, Miaoqian Lin, Murilo Opsfelder Araújo, Nathan Lynch,
Naveen N. Rao, Nayna Jain, Nicholas Piggin, Ning Qiang, Pali Rohár,
Petr Mladek, Rashmica Gupta, Sachin Sant, Scott Cheloha, Segher
Boessenkool, Stephen Rothwell, Uwe Kleine-König, Wolfram Sang, Xiu
Jianfeng, and Zhouyi Zhou.
* tag 'powerpc-6.0-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux: (191 commits)
powerpc/64e: Fix kexec build error
EDAC/ppc_4xx: Include required of_irq header directly
powerpc/pci: Fix PHB numbering when using opal-phbid
powerpc/64: Init jump labels before parse_early_param()
selftests/powerpc: Avoid GCC 12 uninitialised variable warning
powerpc/cell/axon_msi: Fix refcount leak in setup_msi_msg_address
powerpc/xive: Fix refcount leak in xive_get_max_prio
powerpc/spufs: Fix refcount leak in spufs_init_isolated_loader
powerpc/perf: Include caps feature for power10 DD1 version
powerpc: add support for syscall stack randomization
powerpc: Move system_call_exception() to syscall.c
powerpc/powernv: rename remaining rng powernv_ functions to pnv_
powerpc/powernv/kvm: Use darn for H_RANDOM on Power9
powerpc/powernv: Avoid crashing if rng is NULL
selftests/powerpc: Fix matrix multiply assist test
powerpc/signal: Update comment for clarity
powerpc: make facility_unavailable_exception 64s
powerpc/platforms/83xx/suspend: Remove write-only global variable
powerpc/platforms/83xx/suspend: Prevent unloading the driver
powerpc/platforms/83xx/suspend: Reorder to get rid of a forward declaration
...
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In some circumstances it may be interesting to reconfigure the watchdog
from inside the kernel.
On PowerPC, this may helpful before and after a LPAR migration (LPM) is
initiated, because it implies some latencies, watchdog, and especially NMI
watchdog is expected to be triggered during this operation. Reconfiguring
the watchdog with a factor, would prevent it to happen too frequently
during LPM.
Rename lockup_detector_reconfigure() as __lockup_detector_reconfigure() and
create a new function lockup_detector_reconfigure() calling
__lockup_detector_reconfigure() under the protection of watchdog_mutex.
Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
[mpe: Squash in build fix from Laurent, reported by Sachin]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220713154729.80789-3-ldufour@linux.ibm.com
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|
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This reverts commit 2bb2b7b57f81255c13f4395ea911d6bdc70c9fe2.
The testing of 5.19 release candidates revealed missing synchronization
between early and regular console functionality.
It would be possible to start the console kthreads later as a workaround.
But it is clear that console lock serialized console drivers between
each other. It opens a big area of possible problems that were not
considered by people involved in the development and review.
printk() is crucial for debugging kernel issues and console output is
very important part of it. The number of consoles is huge and a proper
review would take some time. As a result it need to be reverted for 5.19.
Link: https://lore.kernel.org/r/YrBdjVwBOVgLfHyb@alley
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20220623145157.21938-7-pmladek@suse.com
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git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull misc updates from Andrew Morton:
"The non-MM patch queue for this merge window.
Not a lot of material this cycle. Many singleton patches against
various subsystems. Most notably some maintenance work in ocfs2
and initramfs"
* tag 'mm-nonmm-stable-2022-05-26' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (65 commits)
kcov: update pos before writing pc in trace function
ocfs2: dlmfs: fix error handling of user_dlm_destroy_lock
ocfs2: dlmfs: don't clear USER_LOCK_ATTACHED when destroying lock
fs/ntfs: remove redundant variable idx
fat: remove time truncations in vfat_create/vfat_mkdir
fat: report creation time in statx
fat: ignore ctime updates, and keep ctime identical to mtime in memory
fat: split fat_truncate_time() into separate functions
MAINTAINERS: add Muchun as a memcg reviewer
proc/sysctl: make protected_* world readable
ia64: mca: drop redundant spinlock initialization
tty: fix deadlock caused by calling printk() under tty_port->lock
relay: remove redundant assignment to pointer buf
fs/ntfs3: validate BOOT sectors_per_clusters
lib/string_helpers: fix not adding strarray to device's resource list
kernel/crash_core.c: remove redundant check of ck_cmdline
ELF, uapi: fixup ELF_ST_TYPE definition
ipc/mqueue: use get_tree_nodev() in mqueue_get_tree()
ipc: update semtimedop() to use hrtimer
ipc/sem: remove redundant assignments
...
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As in "kernel/panic.c: remove CONFIG_PANIC_ON_OOPS_VALUE indirection",
use the IS_ENABLED() helper rather than having a hidden config option.
Link: https://lkml.kernel.org/r/20220321121301.1389693-1-linux@rasmusvillemoes.dk
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Once kthread printing is available, console printing will no longer
occur in the context of the printk caller. However, there are some
special contexts where it is desirable for the printk caller to
directly print out kernel messages. Using pr_flush() to wait for
threaded printers is only possible if the caller is in a sleepable
context and the kthreads are active. That is not always the case.
Introduce printk_prefer_direct_enter() and printk_prefer_direct_exit()
functions to explicitly (and globally) activate/deactivate preferred
direct console printing. The term "direct console printing" refers to
printing to all enabled consoles from the context of the printk
caller. The term "prefer" is used because this type of printing is
only best effort. If the console is currently locked or other
printers are already actively printing, the printk caller will need
to rely on the other contexts to handle the printing.
This preferred direct printing is how all printing has been handled
until now (unless it was explicitly deferred).
When kthread printing is introduced, there may be some unanticipated
problems due to kthreads being unable to flush important messages.
In order to minimize such risks, preferred direct printing is
activated for the primary important messages when the system
experiences general types of major errors. These are:
- emergency reboot/shutdown
- cpu and rcu stalls
- hard and soft lockups
- hung tasks
- warn
- sysrq
Note that since kthread printing does not yet exist, no behavior
changes result from this commit. This is only implementing the
counter and marking the various places where preferred direct
printing is active.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Paul E. McKenney <paulmck@kernel.org> # for RCU
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20220421212250.565456-13-john.ogness@linutronix.de
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Refer to housekeeping APIs using single feature types instead of flags.
This prevents from passing multiple isolation features at once to
housekeeping interfaces, which soon won't be possible anymore as each
isolation features will have their own cpumask.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Juri Lelli <juri.lelli@redhat.com>
Reviewed-by: Phil Auld <pauld@redhat.com>
Link: https://lore.kernel.org/r/20220207155910.527133-5-frederic@kernel.org
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The kernel/sysctl.c is a kitchen sink where everyone leaves their dirty
dishes, this makes it very difficult to maintain.
To help with this maintenance let's start by moving sysctls to places
where they actually belong. The proc sysctl maintainers do not want to
know what sysctl knobs you wish to add for your own piece of code, we
just care about the core logic of proc sysctl.
So, move the watchdog syscl interface to watchdog.c. Use
register_sysctl() to register the sysctl interface to avoid merge
conflicts when different features modify sysctl.c at the same time.
[mcgrof@kernel.org: justify the move on the commit log]
Link: https://lkml.kernel.org/r/20211123202347.818157-5-mcgrof@kernel.org
Signed-off-by: Xiaoming Ni <nixiaoming@huawei.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Iurii Zaikin <yzaikin@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Paul Turner <pjt@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Qing Wang <wangqing@vivo.com>
Cc: Sebastian Reichel <sre@kernel.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Stephen Kitt <steve@sk2.org>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Antti Palosaari <crope@iki.fi>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Clemens Ladisch <clemens@ladisch.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Julia Lawall <julia.lawall@inria.fr>
Cc: Lukas Middendorf <kernel@tuxforce.de>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Phillip Potter <phil@philpotter.co.uk>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Douglas Gilbert <dgilbert@interlog.com>
Cc: James E.J. Bottomley <jejb@linux.ibm.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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The watchdog thread has been replaced by cpu_stop_work, modify the
explanation related.
Link: https://lkml.kernel.org/r/1619687073-24686-2-git-send-email-wangqing@vivo.com
Signed-off-by: Wang Qing <wangqing@vivo.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Cc: Joe Perches <joe@perches.com>
Cc: Stephen Kitt <steve@sk2.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: "Guilherme G. Piccoli" <gpiccoli@canonical.com>
Cc: Qais Yousef <qais.yousef@arm.com>
Cc: Santosh Sivaraj <santosh@fossix.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Commit 9bf3bc949f8a ("watchdog: cleanup handling of false positives")
tried to handle a virtual host stopped by the host a more
straightforward and cleaner way.
But it introduced a risk of false softlockup reports. The virtual host
might be stopped at any time, for example between
kvm_check_and_clear_guest_paused() and is_softlockup(). As a result,
is_softlockup() might read the updated jiffies and detects a softlockup.
A solution might be to put back kvm_check_and_clear_guest_paused() after
is_softlockup() and detect it. But it would put back the cycle that
complicates the logic.
In fact, the handling of all the timestamps is not reliable. The code
does not guarantee when and how many times the timestamps are read. For
example, "period_ts" might be touched anytime also from NMI and re-read in
is_softlockup(). It works just by chance.
Fix all the problems by making the code even more explicit.
1. Make sure that "now" and "period_ts" timestamps are read only once.
They might be changed at anytime by NMI or when the virtual guest is
stopped by the host. Note that "now" timestamp does this implicitly
because "jiffies" is marked volatile.
2. "now" time must be read first. The state of "period_ts" will
decide whether it will be used or the period will get restarted.
3. kvm_check_and_clear_guest_paused() must be called before reading
"period_ts". It touches the variable when the guest was stopped.
As a result, "now" timestamp is used only when the watchdog was not
touched and the guest not stopped in the meantime. "period_ts" is
restarted in all other situations.
Link: https://lkml.kernel.org/r/YKT55gw+RZfyoFf7@alley
Fixes: 9bf3bc949f8aeefeacea4b ("watchdog: cleanup handling of false positives")
Signed-off-by: Petr Mladek <pmladek@suse.com>
Reported-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Commit d6ad3e286d2c ("softlockup: Add sched_clock_tick() to avoid kernel
warning on kgdb resume") introduced touch_softlockup_watchdog_sync().
It solved a problem when the watchdog was touched in an atomic context,
the timer callback was proceed right after releasing interrupts, and the
local clock has not been updated yet. In this case, sched_clock_tick()
was called in watchdog_timer_fn() before updating the timer.
So far so good.
Later commit 5d1c0f4a80a6 ("watchdog: add check for suspended vm in
softlockup detector") added two kvm_check_and_clear_guest_paused()
calls. They touch the watchdog when the guest has been sleeping.
The code makes my head spin around.
Scenario 1:
+ guest did sleep:
+ PVCLOCK_GUEST_STOPPED is set
+ 1st watchdog_timer_fn() invocation:
+ the watchdog is not touched yet
+ is_softlockup() returns too big delay
+ kvm_check_and_clear_guest_paused():
+ clear PVCLOCK_GUEST_STOPPED
+ call touch_softlockup_watchdog_sync()
+ set SOFTLOCKUP_DELAY_REPORT
+ set softlockup_touch_sync
+ return from the timer callback
+ 2nd watchdog_timer_fn() invocation:
+ call sched_clock_tick() even though it is not needed.
The timer callback was invoked again only because the clock
has already been updated in the meantime.
+ call kvm_check_and_clear_guest_paused() that does nothing
because PVCLOCK_GUEST_STOPPED has been cleared already.
+ call update_report_ts() and return. This is fine. Except
that sched_clock_tick() might allow to set it already
during the 1st invocation.
Scenario 2:
+ guest did sleep
+ 1st watchdog_timer_fn() invocation
+ same as in 1st scenario
+ guest did sleep again:
+ set PVCLOCK_GUEST_STOPPED again
+ 2nd watchdog_timer_fn() invocation
+ SOFTLOCKUP_DELAY_REPORT is set from 1st invocation
+ call sched_clock_tick()
+ call kvm_check_and_clear_guest_paused()
+ clear PVCLOCK_GUEST_STOPPED
+ call touch_softlockup_watchdog_sync()
+ set SOFTLOCKUP_DELAY_REPORT
+ set softlockup_touch_sync
+ call update_report_ts() (set real timestamp immediately)
+ return from the timer callback
+ 3rd watchdog_timer_fn() invocation
+ timestamp is set from 2nd invocation
+ softlockup_touch_sync is set but not checked because
the real timestamp is already set
Make the code more straightforward:
1. Always call kvm_check_and_clear_guest_paused() at the very
beginning to handle PVCLOCK_GUEST_STOPPED. It touches the watchdog
when the quest did sleep.
2. Handle the situation when the watchdog has been touched
(SOFTLOCKUP_DELAY_REPORT is set).
Call sched_clock_tick() when touch_*sync() variant was used. It makes
sure that the timestamp will be up to date even when it has been
touched in atomic context or quest did sleep.
As a result, kvm_check_and_clear_guest_paused() is called on a single
location. And the right timestamp is always set when returning from the
timer callback.
Link: https://lkml.kernel.org/r/20210311122130.6788-7-pmladek@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Laurence Oberman <loberman@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincent Whitchurch <vincent.whitchurch@axis.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Any parallel softlockup reports are skipped when one CPU is already
printing backtraces from all CPUs.
The exclusive rights are synchronized using one bit in
soft_lockup_nmi_warn. There is also one memory barrier that does not make
much sense.
Use two barriers on the right location to prevent mixing two reports.
[pmladek@suse.com: use bit lock operations to prevent multiple soft-lockup reports]
Link: https://lkml.kernel.org/r/YFSVsLGVWMXTvlbk@alley
Link: https://lkml.kernel.org/r/20210311122130.6788-6-pmladek@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Laurence Oberman <loberman@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincent Whitchurch <vincent.whitchurch@axis.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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The softlockup detector does some gymnastic with the variable
soft_watchdog_warn. It was added by the commit 58687acba59266735ad
("lockup_detector: Combine nmi_watchdog and softlockup detector").
The purpose is not completely clear. There are the following clues. They
describe the situation how it looked after the above mentioned commit:
1. The variable was checked with a comment "only warn once".
2. The variable was set when softlockup was reported. It was cleared
only when the CPU was not longer in the softlockup state.
3. watchdog_touch_ts was not explicitly updated when the softlockup
was reported. Without this variable, the report would normally
be printed again during every following watchdog_timer_fn()
invocation.
The logic has got even more tangled up by the commit ed235875e2ca98
("kernel/watchdog.c: print traces for all cpus on lockup detection").
After this commit, soft_watchdog_warn is set only when
softlockup_all_cpu_backtrace is enabled. But multiple reports from all
CPUs are prevented by a new variable soft_lockup_nmi_warn.
Conclusion:
The variable probably never worked as intended. In each case, it has not
worked last many years because the softlockup was reported repeatedly
after the full period defined by watchdog_thresh.
The reason is that watchdog gets touched in many known slow paths, for
example, in printk_stack_address(). This code is called also when
printing the softlockup report. It means that the watchdog timestamp gets
updated after each report.
Solution:
Simply remove the logic. People want the periodic report anyway.
Link: https://lkml.kernel.org/r/20210311122130.6788-5-pmladek@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Laurence Oberman <loberman@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincent Whitchurch <vincent.whitchurch@axis.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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