From d7b629a34fc4134a43c730b5f0197855dc4948d0 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 20 May 2009 12:21:19 +0200 Subject: [PATCH] perf_counter: Solve the rotate_ctx vs inherit race differently Instead of disabling RR scheduling of the counters, use a different list that does not get rotated to iterate the counters on inheritance. [ Impact: cleanup, optimization ] Signed-off-by: Peter Zijlstra Cc: Paul Mackerras Cc: Corey Ashford Cc: Peter Zijlstra Cc: Arnaldo Carvalho de Melo Cc: Thomas Gleixner Cc: Marcelo Tosatti Cc: John Kacur LKML-Reference: <20090520102553.237504544@chello.nl> Signed-off-by: Ingo Molnar --- include/linux/perf_counter.h | 1 - kernel/perf_counter.c | 15 +++++---------- 2 files changed, 5 insertions(+), 11 deletions(-) diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h index 13cb2fbbf334..c8c1dfc22c93 100644 --- a/include/linux/perf_counter.h +++ b/include/linux/perf_counter.h @@ -508,7 +508,6 @@ struct perf_counter_context { int nr_counters; int nr_active; int is_active; - int rr_allowed; struct task_struct *task; /* diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c index 4d8f97375f3a..64113e6d1942 100644 --- a/kernel/perf_counter.c +++ b/kernel/perf_counter.c @@ -1120,8 +1120,7 @@ void perf_counter_task_tick(struct task_struct *curr, int cpu) __perf_counter_task_sched_out(ctx); rotate_ctx(&cpuctx->ctx); - if (ctx->rr_allowed) - rotate_ctx(ctx); + rotate_ctx(ctx); perf_counter_cpu_sched_in(cpuctx, cpu); perf_counter_task_sched_in(curr, cpu); @@ -3109,7 +3108,6 @@ __perf_counter_init_context(struct perf_counter_context *ctx, mutex_init(&ctx->mutex); INIT_LIST_HEAD(&ctx->counter_list); INIT_LIST_HEAD(&ctx->event_list); - ctx->rr_allowed = 1; ctx->task = task; } @@ -3350,14 +3348,14 @@ void perf_counter_init_task(struct task_struct *child) */ mutex_lock(&parent_ctx->mutex); - parent_ctx->rr_allowed = 0; - barrier(); /* irqs */ - /* * We dont have to disable NMIs - we are only looking at * the list, not manipulating it: */ - list_for_each_entry(counter, &parent_ctx->counter_list, list_entry) { + list_for_each_entry_rcu(counter, &parent_ctx->event_list, event_entry) { + if (counter != counter->group_leader) + continue; + if (!counter->hw_event.inherit) continue; @@ -3366,9 +3364,6 @@ void perf_counter_init_task(struct task_struct *child) break; } - barrier(); /* irqs */ - parent_ctx->rr_allowed = 1; - mutex_unlock(&parent_ctx->mutex); } -- 2.39.5