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perf_counter: Solve the rotate_ctx vs inherit race differently

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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 <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <20090520102553.237504544@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-05-20 12:21:19 +02:00 committed by Ingo Molnar
parent c44d70a340
commit d7b629a34f
2 changed files with 5 additions and 11 deletions
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1
include/linux/perf_counter.h
View File

@ -508,7 +508,6 @@ struct perf_counter_context {
int nr_counters;
int nr_active;
int is_active;
int rr_allowed;
struct task_struct *task;
/*

13
kernel/perf_counter.c
View File

@ -1120,7 +1120,6 @@ 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);
perf_counter_cpu_sched_in(cpuctx, 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);
}