From: Stephane Eranian <eranian@google.com>
Date: Fri, 18 Feb 2011 12:40:01 +0000 (+0200)
Subject: perf_events: Fix rcu and locking issues with cgroup support
X-Git-Tag: v2.6.39-rc1~510^2~50
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3f7cce3c18188a067d463749168bdda5abc5b0f7;p=pandora-kernel.git

perf_events: Fix rcu and locking issues with cgroup support

This patches ensures that we do not end up calling
perf_cgroup_from_task() when there is no cgroup event.
This avoids potential RCU and locking issues.

The change in perf_cgroup_set_timestamp() ensures we
check against ctx->nr_cgroups. It also avoids calling
perf_clock() tiwce in a row. It also ensures we do need
to grab ctx->lock before calling the function.

We drop update_cgrp_time() from task_clock_event_read()
because it is not needed. This also avoids having to
deal with perf_cgroup_from_task().

Thanks to Peter Zijlstra for his help on this.

Signed-off-by: Stephane Eranian <eranian@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <4d5e76b8.815bdf0a.7ac3.774f@mx.google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

Reading git-diff-tree failed