https://github.com/torvalds/linux
Revision 2630cde26711dab0d0b56a8be1616475be646d13 authored by Michal Koutný on 17 September 2021, 15:30:37 UTC, committed by Peter Zijlstra on 01 October 2021, 11:57:57 UTC
Since commit a7b359fc6a37 ("sched/fair: Correctly insert cfs_rq's to list on unthrottle") we add cfs_rqs with no runnable tasks but not fully decayed into the load (leaf) list. We may ignore adding some ancestors and therefore breaking tmp_alone_branch invariant. This broke LTP test cfs_bandwidth01 and it was partially fixed in commit fdaba61ef8a2 ("sched/fair: Ensure that the CFS parent is added after unthrottling"). I noticed the named test still fails even with the fix (but with low probability, 1 in ~1000 executions of the test). The reason is when bailing out of unthrottle_cfs_rq early, we may miss adding ancestors of the unthrottled cfs_rq, thus, not joining tmp_alone_branch properly. Fix this by adding ancestors if we notice the unthrottled cfs_rq was added to the load list. Fixes: a7b359fc6a37 ("sched/fair: Correctly insert cfs_rq's to list on unthrottle") Signed-off-by: Michal Koutný <mkoutny@suse.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Reviewed-by: Odin Ugedal <odin@uged.al> Link: https://lore.kernel.org/r/20210917153037.11176-1-mkoutny@suse.com
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Tip revision: 2630cde26711dab0d0b56a8be1616475be646d13 authored by Michal Koutný on 17 September 2021, 15:30:37 UTC
sched/fair: Add ancestors of unthrottled undecayed cfs_rq
sched/fair: Add ancestors of unthrottled undecayed cfs_rq
Tip revision: 2630cde
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