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perf, core: Fix initial task_ctx/event installation

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A lost Quilt refresh of 2c29ef0fef (perf: Simplify and fix
__perf_install_in_context()) is causing grief and lockups,
reported by Jiri Olsa.

When installing an event in a task context, there's a number of
issues:

 - there might not be an existing task context, in which case
   we should install the now current context;

 - there might already be a context, not the current one, in
   which case we should de-schedule the old and install the new;

these cases were dealt with in the lost refresh, however there is one
further case that was found in testing:

 - there might already be a context, the current one, in which
   case we should still de-schedule, and should take care
   to re-install it (note that task_ctx_sched_out() clears
   cpuctx->task_ctx).

Reported-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1307399008.2497.971.camel@laptop
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2011-06-07 00:23:28 +02:00 committed by Ingo Molnar
parent 3ce2a0bc9d
commit b58f6b0dd3
1 changed files with 17 additions and 11 deletions
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28
kernel/events/core.c
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@ -1505,25 +1505,31 @@ static int __perf_install_in_context(void *info)
struct perf_event_context *task_ctx = cpuctx->task_ctx;
struct task_struct *task = current;
perf_ctx_lock(cpuctx, cpuctx->task_ctx);
perf_ctx_lock(cpuctx, task_ctx);
perf_pmu_disable(cpuctx->ctx.pmu);
/*
* If there was an active task_ctx schedule it out.
*/
if (task_ctx) {
if (task_ctx)
task_ctx_sched_out(task_ctx);
/*
* If the context we're installing events in is not the
* active task_ctx, flip them.
*/
if (ctx->task && task_ctx != ctx) {
raw_spin_unlock(&cpuctx->ctx.lock);
raw_spin_lock(&ctx->lock);
cpuctx->task_ctx = task_ctx = ctx;
}
/*
* If the context we're installing events in is not the
* active task_ctx, flip them.
*/
if (ctx->task && task_ctx != ctx) {
if (task_ctx)
raw_spin_unlock(&task_ctx->lock);
raw_spin_lock(&ctx->lock);
task_ctx = ctx;
}
if (task_ctx) {
cpuctx->task_ctx = task_ctx;
task = task_ctx->task;
}
cpu_ctx_sched_out(cpuctx, EVENT_ALL);
update_context_time(ctx);