Hi stable maintainers,
Please consider the following commit for 3.2-3.12 kernels:
commit f9f9ffc237dd924f048204e8799da74f9ecf40cf
Author: Ben Segall <bsegall@xxxxxxxxxx>
Date: Wed Oct 16 11:16:32 2013 -0700
sched: Avoid throttle_cfs_rq() racing with period_timer stopping
throttle_cfs_rq() doesn't check to make sure that period_timer is
running,
and while update_curr/assign_cfs_runtime does, a concurrently running
period_timer on another cpu could cancel itself between this cpu's
update_curr and throttle_cfs_rq(). If there are no other cfs_rqs
running
in the tg to restart the timer, this causes the cfs_rq to be stranded
forever.
Fix this by calling __start_cfs_bandwidth() in throttle if the timer is
inactive.
(Also add some sched_debug lines for cfs_bandwidth.)
Tested: make a run/sleep task in a cgroup, loop switching the cgroup
between 1ms/100ms quota and unlimited, checking for timer_active=0 and
throttled=1 as a failure. With the throttle_cfs_rq() change
commented out
this fails, with the full patch it passes.
Signed-off-by: Ben Segall <bsegall@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: pjt@xxxxxxxxxx
Link:
http://lkml.kernel.org/r/20131016181632.22647.84174.stgit@xxxxxxxxxxxxxxxxxxxxx.
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
A bug was noticed when running VMs and setting cpu.cfs_quota for that
vcpu's cpu cgroup. Occasionally when rebooting or shutting down a VM the
vcpu task would get stuck in a state where the task has a timer disabled
and no longer gets scheduled on the cfs_rq. This patch fixes
throttle_cfs_rq by checking if the timer is not active, and then calling
__start_cfs_bandwidth.
I have only built this against 3.2, 3.5, 3.8 and 3.11. 3.2 and 3.5
required trivial backports. While, 3.8/3.11 were clean cherry-picks.
BugLink: http://bugs.launchpad.net/bugs/1259645
Thanks,
--chris j arges
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