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2016-08-22rcu: Use RCU's online-CPU state for expedited IPI retryPaul E. McKenney1-6/+5
This commit improves the accuracy of the interaction between CPU hotplug operations and RCU's expedited grace periods by using RCU's online-CPU state to determine when failed IPIs should be retried. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2016-08-22rcu: Exclude RCU-offline CPUs from expedited grace periodsPaul E. McKenney1-1/+2
The expedited RCU grace periods currently rely on a failure indication from smp_call_function_single() to determine that a given CPU is offline. This works after a fashion, but is more contorted and less precise than relying on RCU's internal state. This commit therefore takes a first step towards relying on internal state. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2016-08-22rcu: Make expedited RCU CPU stall warnings respond to controlsPaul E. McKenney1-0/+3
The expedited RCU CPU stall warnings currently responds to neither the panic_on_rcu_stall sysctl setting nor the rcupdate.rcu_cpu_stall_suppress kernel boot parameter. This commit therefore updates the expedited code to respond to these two controls. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2016-08-22rcu: Stop disabling expedited RCU CPU stall warningsPaul E. McKenney1-6/+1
Now that RCU expedited grace periods are always driven by a workqueue, there is no need to account for signal reception, and thus no need to disable expedited RCU CPU stall warnings due to signal reception. This commit therefore removes the signal-reception checks, leaving a WARN_ON() to catch possible future bugs. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2016-08-22rcu: Drive expedited grace periods from workqueuePaul E. McKenney1-6/+42
The current implementation of expedited grace periods has the user task drive the grace period. This works, but has downsides: (1) The user task must awaken tasks piggybacking on this grace period, which can result in latencies rivaling that of the grace period itself, and (2) User tasks can receive signals, which interfere with RCU CPU stall warnings. This commit therefore uses workqueues to drive the grace periods, so that the user task need not do the awakening. A subsequent commit will remove the now-unnecessary code allowing for signals. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2016-08-22rcu: Consolidate expedited grace period machineryPaul E. McKenney1-33/+29
The functions synchronize_rcu_expedited() and synchronize_sched_expedited() have nearly identical code. This commit therefore consolidates this code into a new _synchronize_rcu_expedited() function. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2016-07-25Merge branch 'locking-core-for-linus' of ↵Linus Torvalds1-1/+0
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull locking updates from Ingo Molnar: "The locking tree was busier in this cycle than the usual pattern - a couple of major projects happened to coincide. The main changes are: - implement the atomic_fetch_{add,sub,and,or,xor}() API natively across all SMP architectures (Peter Zijlstra) - add atomic_fetch_{inc/dec}() as well, using the generic primitives (Davidlohr Bueso) - optimize various aspects of rwsems (Jason Low, Davidlohr Bueso, Waiman Long) - optimize smp_cond_load_acquire() on arm64 and implement LSE based atomic{,64}_fetch_{add,sub,and,andnot,or,xor}{,_relaxed,_acquire,_release}() on arm64 (Will Deacon) - introduce smp_acquire__after_ctrl_dep() and fix various barrier mis-uses and bugs (Peter Zijlstra) - after discovering ancient spin_unlock_wait() barrier bugs in its implementation and usage, strengthen its semantics and update/fix usage sites (Peter Zijlstra) - optimize mutex_trylock() fastpath (Peter Zijlstra) - ... misc fixes and cleanups" * 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (67 commits) locking/atomic: Introduce inc/dec variants for the atomic_fetch_$op() API locking/barriers, arch/arm64: Implement LDXR+WFE based smp_cond_load_acquire() locking/static_keys: Fix non static symbol Sparse warning locking/qspinlock: Use __this_cpu_dec() instead of full-blown this_cpu_dec() locking/atomic, arch/tile: Fix tilepro build locking/atomic, arch/m68k: Remove comment locking/atomic, arch/arc: Fix build locking/Documentation: Clarify limited control-dependency scope locking/atomic, arch/rwsem: Employ atomic_long_fetch_add() locking/atomic, arch/qrwlock: Employ atomic_fetch_add_acquire() locking/atomic, arch/mips: Convert to _relaxed atomics locking/atomic, arch/alpha: Convert to _relaxed atomics locking/atomic: Remove the deprecated atomic_{set,clear}_mask() functions locking/atomic: Remove linux/atomic.h:atomic_fetch_or() locking/atomic: Implement atomic{,64,_long}_fetch_{add,sub,and,andnot,or,xor}{,_relaxed,_acquire,_release}() locking/atomic: Fix atomic64_relaxed() bits locking/atomic, arch/xtensa: Implement atomic_fetch_{add,sub,and,or,xor}() locking/atomic, arch/x86: Implement atomic{,64}_fetch_{add,sub,and,or,xor}() locking/atomic, arch/tile: Implement atomic{,64}_fetch_{add,sub,and,or,xor}() locking/atomic, arch/sparc: Implement atomic{,64}_fetch_{add,sub,and,or,xor}() ...
2016-06-15rcu: Correctly handle sparse possible cpusMark Rutland1-9/+7
In many cases in the RCU tree code, we iterate over the set of cpus for a leaf node described by rcu_node::grplo and rcu_node::grphi, checking per-cpu data for each cpu in this range. However, if the set of possible cpus is sparse, some cpus described in this range are not possible, and thus no per-cpu region will have been allocated (or initialised) for them by the generic percpu code. Erroneous accesses to a per-cpu area for these !possible cpus may fault or may hit other data depending on the addressed generated when the erroneous per cpu offset is applied. In practice, both cases have been observed on arm64 hardware (the former being silent, but detectable with additional patches). To avoid issues resulting from this, we must iterate over the set of *possible* cpus for a given leaf node. This patch add a new helper, for_each_leaf_node_possible_cpu, to enable this. As iteration is often intertwined with rcu_node local bitmask manipulation, a new leaf_node_cpu_bit helper is added to make this simpler and more consistent. The RCU tree code is made to use both of these where appropriate. Without this patch, running reboot at a shell can result in an oops like: [ 3369.075979] Unable to handle kernel paging request at virtual address ffffff8008b21b4c [ 3369.083881] pgd = ffffffc3ecdda000 [ 3369.087270] [ffffff8008b21b4c] *pgd=00000083eca48003, *pud=00000083eca48003, *pmd=0000000000000000 [ 3369.096222] Internal error: Oops: 96000007 [#1] PREEMPT SMP [ 3369.101781] Modules linked in: [ 3369.104825] CPU: 2 PID: 1817 Comm: NetworkManager Tainted: G W 4.6.0+ #3 [ 3369.121239] task: ffffffc0fa13e000 ti: ffffffc3eb940000 task.ti: ffffffc3eb940000 [ 3369.128708] PC is at sync_rcu_exp_select_cpus+0x188/0x510 [ 3369.134094] LR is at sync_rcu_exp_select_cpus+0x104/0x510 [ 3369.139479] pc : [<ffffff80081109a8>] lr : [<ffffff8008110924>] pstate: 200001c5 [ 3369.146860] sp : ffffffc3eb9435a0 [ 3369.150162] x29: ffffffc3eb9435a0 x28: ffffff8008be4f88 [ 3369.155465] x27: ffffff8008b66c80 x26: ffffffc3eceb2600 [ 3369.160767] x25: 0000000000000001 x24: ffffff8008be4f88 [ 3369.166070] x23: ffffff8008b51c3c x22: ffffff8008b66c80 [ 3369.171371] x21: 0000000000000001 x20: ffffff8008b21b40 [ 3369.176673] x19: ffffff8008b66c80 x18: 0000000000000000 [ 3369.181975] x17: 0000007fa951a010 x16: ffffff80086a30f0 [ 3369.187278] x15: 0000007fa9505590 x14: 0000000000000000 [ 3369.192580] x13: ffffff8008b51000 x12: ffffffc3eb940000 [ 3369.197882] x11: 0000000000000006 x10: ffffff8008b51b78 [ 3369.203184] x9 : 0000000000000001 x8 : ffffff8008be4000 [ 3369.208486] x7 : ffffff8008b21b40 x6 : 0000000000001003 [ 3369.213788] x5 : 0000000000000000 x4 : ffffff8008b27280 [ 3369.219090] x3 : ffffff8008b21b4c x2 : 0000000000000001 [ 3369.224406] x1 : 0000000000000001 x0 : 0000000000000140 ... [ 3369.972257] [<ffffff80081109a8>] sync_rcu_exp_select_cpus+0x188/0x510 [ 3369.978685] [<ffffff80081128b4>] synchronize_rcu_expedited+0x64/0xa8 [ 3369.985026] [<ffffff80086b987c>] synchronize_net+0x24/0x30 [ 3369.990499] [<ffffff80086ddb54>] dev_deactivate_many+0x28c/0x298 [ 3369.996493] [<ffffff80086b6bb8>] __dev_close_many+0x60/0xd0 [ 3370.002052] [<ffffff80086b6d48>] __dev_close+0x28/0x40 [ 3370.007178] [<ffffff80086bf62c>] __dev_change_flags+0x8c/0x158 [ 3370.012999] [<ffffff80086bf718>] dev_change_flags+0x20/0x60 [ 3370.018558] [<ffffff80086cf7f0>] do_setlink+0x288/0x918 [ 3370.023771] [<ffffff80086d0798>] rtnl_newlink+0x398/0x6a8 [ 3370.029158] [<ffffff80086cee84>] rtnetlink_rcv_msg+0xe4/0x220 [ 3370.034891] [<ffffff80086e274c>] netlink_rcv_skb+0xc4/0xf8 [ 3370.040364] [<ffffff80086ced8c>] rtnetlink_rcv+0x2c/0x40 [ 3370.045663] [<ffffff80086e1fe8>] netlink_unicast+0x160/0x238 [ 3370.051309] [<ffffff80086e24b8>] netlink_sendmsg+0x2f0/0x358 [ 3370.056956] [<ffffff80086a0070>] sock_sendmsg+0x18/0x30 [ 3370.062168] [<ffffff80086a21cc>] ___sys_sendmsg+0x26c/0x280 [ 3370.067728] [<ffffff80086a30ac>] __sys_sendmsg+0x44/0x88 [ 3370.073027] [<ffffff80086a3100>] SyS_sendmsg+0x10/0x20 [ 3370.078153] [<ffffff8008085e70>] el0_svc_naked+0x24/0x28 Signed-off-by: Mark Rutland <mark.rutland@arm.com> Reported-by: Dennis Chen <dennis.chen@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Lai Jiangshan <jiangshanlai@gmail.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Steve Capper <steve.capper@arm.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Will Deacon <will.deacon@arm.com> Cc: linux-kernel@vger.kernel.org Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2016-06-14rcu: Move expedited code from tree_plugin.h to tree_exp.hPaul E. McKenney1-0/+94
People have been having some difficulty finding their way around the RCU code. This commit therefore pulls some of the expedited grace-period code from tree_plugin.h to a new tree_exp.h file. This commit is strictly code movement. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2016-06-14rcu: Move expedited code from tree.c to tree_exp.hPaul E. McKenney1-0/+564
People have been having some difficulty finding their way around the RCU code. This commit therefore pulls some of the expedited grace-period code from tree.c to a new tree_exp.h file. This commit is strictly code movement, with the exception of a forward declaration that was added for the sync_sched_exp_online_cleanup() function. A subsequent commit will move the remaining expedited grace-period code from tree_plugin.h to tree_exp.h. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>