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authorOleg Nesterov <oleg@redhat.com>2015-02-12 20:59:13 +0100
committerIngo Molnar <mingo@kernel.org>2015-02-18 14:27:40 +0100
commitbc9560155f4063bbc9be71bd69d6726d41b47653 (patch)
tree9d4be1d4a9526b0b0d9e74cfb335ad696195685f /kernel/context_tracking.c
parent06b1f8083d6ed379ec1207a96339f23e8f7abfcf (diff)
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sched/completion: Serialize completion_done() with complete()
Commit de30ec47302c "Remove unnecessary ->wait.lock serialization when reading completion state" was not correct, without lock/unlock the code like stop_machine_from_inactive_cpu() while (!completion_done()) cpu_relax(); can return before complete() finishes its spin_unlock() which writes to this memory. And spin_unlock_wait(). While at it, change try_wait_for_completion() to use READ_ONCE(). Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reported-by: Davidlohr Bueso <dave@stgolabs.net> Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> [ Added a comment with the barrier. ] Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nicholas Mc Guire <der.herr@hofr.at> Cc: raghavendra.kt@linux.vnet.ibm.com Cc: waiman.long@hp.com Fixes: de30ec47302c ("sched/completion: Remove unnecessary ->wait.lock serialization when reading completion state") Link: http://lkml.kernel.org/r/20150212195913.GA30430@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/context_tracking.c')
0 files changed, 0 insertions, 0 deletions
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