diff options
| author | Aaron Tomlin <atomlin@redhat.com> | 2014-05-22 10:54:31 +1000 |
|---|---|---|
| committer | Stephen Rothwell <sfr@canb.auug.org.au> | 2014-06-03 18:50:31 +1000 |
| commit | 5613be2dffc973acc7f5fe67f3085178bb1591b4 (patch) | |
| tree | 6e6b5f6a45d7180e77e41e7f98fd6d23c55782b4 /Documentation/sysctl | |
| parent | d7dbe871946d1575523190b0a3d4f94f50919576 (diff) | |
kernel/watchdog.c: print traces for all cpus on lockup detection
A 'softlockup' is defined as a bug that causes the kernel to loop in
kernel mode for more than a predefined period to time, without giving
other tasks a chance to run.
Currently, upon detection of this condition by the per-cpu watchdog task,
debug information (including a stack trace) is sent to the system log.
On some occasions, we have observed that the "victim" rather than the
actual "culprit" (i.e. the owner/holder of the contended resource) is
reported to the user. Often this information has proven to be
insufficient to assist debugging efforts.
To avoid loss of useful debug information, for architectures which support
NMI, this patch makes it possible to improve soft lockup reporting. This
is accomplished by issuing an NMI to each cpu to obtain a stack trace.
If NMI is not supported we just revert back to the old method. A sysctl
and boot-time parameter is available to toggle this feature.
[dzickus@redhat.com: add CONFIG_SMP in certain areas]
Signed-off-by: Aaron Tomlin <atomlin@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Mateusz Guzik <mguzik@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'Documentation/sysctl')
| -rw-r--r-- | Documentation/sysctl/kernel.txt | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt index 708bb7f1b7e..c14374e7177 100644 --- a/Documentation/sysctl/kernel.txt +++ b/Documentation/sysctl/kernel.txt @@ -75,6 +75,7 @@ show up in /proc/sys/kernel: - shmall - shmmax [ sysv ipc ] - shmmni +- softlockup_all_cpu_backtrace - stop-a [ SPARC only ] - sysrq ==> Documentation/sysrq.txt - sysctl_writes_strict @@ -783,6 +784,22 @@ via the /proc/sys interface: ============================================================== +softlockup_all_cpu_backtrace: + +This value controls the soft lockup detector thread's behavior +when a soft lockup condition is detected as to whether or not +to gather further debug information. If enabled, each cpu will +be issued an NMI and instructed to capture stack trace. + +This feature is only applicable for architectures which support +NMI. + +0: do nothing. This is the default behavior. + +1: on detection capture more debug information. + +============================================================== + tainted: Non-zero if the kernel has been tainted. Numeric values, which |