commit 1ee14e6c8cddeeb8a490d7b54cd9016e4bb900b4
author Ben Segall <bsegall@google.com> Wed Oct 16 11:16:12 2013 -0700
committer Ingo Molnar <mingo@kernel.org> Tue Oct 29 12:02:19 2013 +0100
tree 1fe48f0122fdda3bf75bb637a9e103e541598e8a
parent ac9ff7997b6f2b31949dcd2495ac671fd9ddc990

sched: Fix race on toggling cfs_bandwidth_used

When we transition cfs_bandwidth_used to false, any currently
throttled groups will incorrectly return false from cfs_rq_throttled.
While tg_set_cfs_bandwidth will unthrottle them eventually, currently
running code (including at least dequeue_task_fair and
distribute_cfs_runtime) will cause errors.

Fix this by turning off cfs_bandwidth_used only after unthrottling all
cfs_rqs.

Tested: toggle bandwidth back and forth on a loaded cgroup. Caused
crashes in minutes without the patch, hasn't crashed with it.

Signed-off-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: pjt@google.com
Link: http://lkml.kernel.org/r/20131016181611.22647.80365.stgit@sword-of-the-dawn.mtv.corp.google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>