Commit d6ff86cf authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar

perf: Optimize perf_event_task_ctx()

Remove a rcu_read_{,un}lock() pair and a few conditionals.

We can remove the rcu_read_lock() by increasing the scope of one
in the calling function.

We can do away with the system_state check if the machine still
boots after this patch (seems to be the case).

We can do away with the list_empty() check because the bare
list_for_each_entry_rcu() reduces to that now that we've removed
everything else.
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <20091120212508.452227115@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 81520183
......@@ -3267,15 +3267,10 @@ static void perf_event_task_ctx(struct perf_event_context *ctx,
{
struct perf_event *event;
if (system_state != SYSTEM_RUNNING || list_empty(&ctx->event_list))
return;
rcu_read_lock();
list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
if (perf_event_task_match(event))
perf_event_task_output(event, task_event);
}
rcu_read_unlock();
}
static void perf_event_task_event(struct perf_task_event *task_event)
......@@ -3283,11 +3278,11 @@ static void perf_event_task_event(struct perf_task_event *task_event)
struct perf_cpu_context *cpuctx;
struct perf_event_context *ctx = task_event->task_ctx;
rcu_read_lock();
cpuctx = &get_cpu_var(perf_cpu_context);
perf_event_task_ctx(&cpuctx->ctx, task_event);
put_cpu_var(perf_cpu_context);
rcu_read_lock();
if (!ctx)
ctx = rcu_dereference(task_event->task->perf_event_ctxp);
if (ctx)
......
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