From e5289d4a181fb6c0b7a7607649af2ffdc491335c Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 19 Jun 2009 13:22:51 +0200 Subject: [PATCH] perf_counter: Simplify and fix task migration counting The task migrations counter was causing rare and hard to decypher memory corruptions under load. After a day of debugging and bisection we found that the problem was introduced with: 3f731ca: perf_counter: Fix cpu migration counter Turning them off fixes the crashes. Incidentally, the whole perf_counter_task_migration() logic can be done simpler as well, by injecting a proper sw-counter event. This cleanup also fixed the crashes. The precise failure mode is not completely clear yet, but we are clearly not unhappy about having a fix ;-) Signed-off-by: Peter Zijlstra Cc: Mike Galbraith Cc: Paul Mackerras Cc: Corey Ashford Cc: Marcelo Tosatti Cc: Arnaldo Carvalho de Melo LKML-Reference: Signed-off-by: Ingo Molnar --- include/linux/perf_counter.h | 4 ---- kernel/perf_counter.c | 23 +---------------------- kernel/sched.c | 3 ++- 3 files changed, 3 insertions(+), 27 deletions(-) diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h index e7e7e0242767..89698d8aba5c 100644 --- a/include/linux/perf_counter.h +++ b/include/linux/perf_counter.h @@ -682,8 +682,6 @@ static inline void perf_counter_mmap(struct vm_area_struct *vma) extern void perf_counter_comm(struct task_struct *tsk); extern void perf_counter_fork(struct task_struct *tsk); -extern void perf_counter_task_migration(struct task_struct *task, int cpu); - extern struct perf_callchain_entry *perf_callchain(struct pt_regs *regs); extern int sysctl_perf_counter_paranoid; @@ -724,8 +722,6 @@ static inline void perf_counter_mmap(struct vm_area_struct *vma) { } static inline void perf_counter_comm(struct task_struct *tsk) { } static inline void perf_counter_fork(struct task_struct *tsk) { } static inline void perf_counter_init(void) { } -static inline void perf_counter_task_migration(struct task_struct *task, - int cpu) { } #endif #endif /* __KERNEL__ */ diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c index 7e9108efd305..8d4f0dd41c22 100644 --- a/kernel/perf_counter.c +++ b/kernel/perf_counter.c @@ -124,7 +124,7 @@ void perf_enable(void) static void get_ctx(struct perf_counter_context *ctx) { - atomic_inc(&ctx->refcount); + WARN_ON(!atomic_inc_not_zero(&ctx->refcount)); } static void free_ctx(struct rcu_head *head) @@ -3467,27 +3467,6 @@ static const struct pmu perf_ops_task_clock = { .read = task_clock_perf_counter_read, }; -/* - * Software counter: cpu migrations - */ -void perf_counter_task_migration(struct task_struct *task, int cpu) -{ - struct perf_cpu_context *cpuctx = &per_cpu(perf_cpu_context, cpu); - struct perf_counter_context *ctx; - - perf_swcounter_ctx_event(&cpuctx->ctx, PERF_TYPE_SOFTWARE, - PERF_COUNT_SW_CPU_MIGRATIONS, - 1, 1, NULL, 0); - - ctx = perf_pin_task_context(task); - if (ctx) { - perf_swcounter_ctx_event(ctx, PERF_TYPE_SOFTWARE, - PERF_COUNT_SW_CPU_MIGRATIONS, - 1, 1, NULL, 0); - perf_unpin_context(ctx); - } -} - #ifdef CONFIG_EVENT_PROFILE void perf_tpcounter_event(int event_id) { diff --git a/kernel/sched.c b/kernel/sched.c index 8fb88a906aaa..f46540b359c0 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -1978,7 +1978,8 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu) if (task_hot(p, old_rq->clock, NULL)) schedstat_inc(p, se.nr_forced2_migrations); #endif - perf_counter_task_migration(p, new_cpu); + perf_swcounter_event(PERF_COUNT_SW_CPU_MIGRATIONS, + 1, 1, NULL, 0); } p->se.vruntime -= old_cfsrq->min_vruntime - new_cfsrq->min_vruntime; -- 2.11.0