tree 44daa0dafa49cedc9301efd1417c6c2ac338c1c7
parent 88b8dac0a14c511ff41486b83a8c3d688936eec0
author Peter Zijlstra <peterz@infradead.org> 1340364965 +0200
committer Ingo Molnar <mingo@kernel.org> 1343131100 +0200

sched: Fix race in task_group()

Stefan reported a crash on a kernel before a3e5d1091c1 ("sched:
Don't call task_group() too many times in set_task_rq()"), he
found the reason to be that the multiple task_group()
invocations in set_task_rq() returned different values.

Looking at all that I found a lack of serialization and plain
wrong comments.

The below tries to fix it using an extra pointer which is
updated under the appropriate scheduler locks. Its not pretty,
but I can't really see another way given how all the cgroup
stuff works.

Reported-and-tested-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1340364965.18025.71.camel@twins
Signed-off-by: Ingo Molnar <mingo@kernel.org>