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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2012-01-11 13:11:12 +0100
committerIngo Molnar <mingo@elte.hu>2012-01-11 17:15:12 +0100
commitbced76aeaca03b45e3b4bdb868cada328e497847 (patch)
treee2965b6cfecdc257a01b89ec6780b8de3b2e6d39 /init
parent6db9dc150eabce7053c8df2a2146aa0d6748ec42 (diff)
sched: Fix lockup by limiting load-balance retries on lock-break
Eric and David reported dead machines and traced it to commit a195f004 ("sched: Fix load-balance lock-breaking"), it turns out there's still a scenario where we can end up re-trying forever. Since there is no strict forward progress guarantee in the load-balance iteration we can get stuck re-retrying the same task-set over and over. Creating a forward progress guarantee with the existing structure is somewhat non-trivial, for now simply terminate the retry loop after a few tries. Reported-by: Eric Dumazet <eric.dumazet@gmail.com> Tested-by: Eric Dumazet <eric.dumazet@gmail.com> Reported-by: David Ahern <dsahern@gmail.com> [ logic cleanup as suggested by Eric ] Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Suresh Siddha <suresh.b.siddha@intel.com> Link: http://lkml.kernel.org/r/1326297936.2442.157.camel@twins Signed-off-by: Ingo Molnar <mingo@elte.hu>
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