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 <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>
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 13cb2fb..c8c1dfc2 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -508,7 +508,6 @@
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 4d8f973..64113e6 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1120,8 +1120,7 @@
__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 @@
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 @@
*/
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 @@
break;
}
- barrier(); /* irqs */
- parent_ctx->rr_allowed = 1;
-
mutex_unlock(&parent_ctx->mutex);
}