From 40bea039593dfc7f3f9814dab844f6db43ae580b Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Wed, 13 Aug 2014 18:50:16 +0200 Subject: [PATCH] nohz: Restore NMI safe local irq work for local nohz kick The local nohz kick is currently used by perf which needs it to be NMI-safe. Recent commit though (7d1311b93e58ed55f3a31cc8f94c4b8fe988a2b9) changed its implementation to fire the local kick using the remote kick API. It was convenient to make the code more generic but the remote kick isn't NMI-safe. As a result: WARNING: CPU: 3 PID: 18062 at kernel/irq_work.c:72 irq_work_queue_on+0x11e/0x140() CPU: 3 PID: 18062 Comm: trinity-subchil Not tainted 3.16.0+ #34 0000000000000009 00000000903774d1 ffff880244e06c00 ffffffff9a7f1e37 0000000000000000 ffff880244e06c38 ffffffff9a0791dd ffff880244fce180 0000000000000003 ffff880244e06d58 ffff880244e06ef8 0000000000000000 Call Trace: [] dump_stack+0x4e/0x7a [] warn_slowpath_common+0x7d/0xa0 [] warn_slowpath_null+0x1a/0x20 [] irq_work_queue_on+0x11e/0x140 [] tick_nohz_full_kick_cpu+0x57/0x90 [] __perf_event_overflow+0x275/0x350 [] ? perf_event_task_disable+0xa0/0xa0 [] ? x86_perf_event_set_period+0xbf/0x150 [] perf_event_overflow+0x14/0x20 [] intel_pmu_handle_irq+0x206/0x410 [] ? arch_vtime_task_switch+0x63/0x130 [] perf_event_nmi_handler+0x2b/0x50 [] nmi_handle+0xd2/0x390 [] ? nmi_handle+0x5/0x390 [] ? lock_release+0xab/0x330 [] default_do_nmi+0x72/0x1c0 [] ? cpuacct_account_field+0xcf/0x200 [] do_nmi+0xb8/0x100 Lets fix this by restoring the use of local irq work for the nohz local kick. Reported-by: Catalin Iacob Reported-and-tested-by: Dave Jones Cc: Peter Zijlstra Cc: Thomas Gleixner Signed-off-by: Frederic Weisbecker --- include/linux/tick.h | 7 +------ kernel/time/tick-sched.c | 14 ++++++++++++++ 2 files changed, 15 insertions(+), 6 deletions(-) diff --git a/include/linux/tick.h b/include/linux/tick.h index 059052306831..9a82c7dc3fdd 100644 --- a/include/linux/tick.h +++ b/include/linux/tick.h @@ -183,13 +183,8 @@ static inline bool tick_nohz_full_cpu(int cpu) extern void tick_nohz_init(void); extern void __tick_nohz_full_check(void); +extern void tick_nohz_full_kick(void); extern void tick_nohz_full_kick_cpu(int cpu); - -static inline void tick_nohz_full_kick(void) -{ - tick_nohz_full_kick_cpu(smp_processor_id()); -} - extern void tick_nohz_full_kick_all(void); extern void __tick_nohz_task_switch(struct task_struct *tsk); #else diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 99aa6ee3908f..f654a8a298fa 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -224,6 +224,20 @@ static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = { .func = nohz_full_kick_work_func, }; +/* + * Kick this CPU if it's full dynticks in order to force it to + * re-evaluate its dependency on the tick and restart it if necessary. + * This kick, unlike tick_nohz_full_kick_cpu() and tick_nohz_full_kick_all(), + * is NMI safe. + */ +void tick_nohz_full_kick(void) +{ + if (!tick_nohz_full_cpu(smp_processor_id())) + return; + + irq_work_queue(&__get_cpu_var(nohz_full_kick_work)); +} + /* * Kick the CPU if it's full dynticks in order to force it to * re-evaluate its dependency on the tick and restart it if necessary. -- 2.20.1