On Wed, 6 Jan 2016, tip-bot for Sebastian Andrzej Siewior wrote: > Commit-ID: 093e5840ae76f1082633503964d035f40ed0216d > Gitweb: http://git.kernel.org/tip/093e5840ae76f1082633503964d035f40ed0216d > Author: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> > AuthorDate: Mon, 21 Dec 2015 18:17:10 +0100 > Committer: Ingo Molnar <mingo@xxxxxxxxxx> > CommitDate: Wed, 6 Jan 2016 11:01:07 +0100 > > sched/core: Reset task's lockless wake-queues on fork() > > In the following commit: > > 7675104990ed ("sched: Implement lockless wake-queues") > > we gained lockless wake-queues. > > The -RT kernel managed to lockup itself with those. There could be multiple > attempts for task X to enqueue it for a wakeup _even_ if task X is already > running. > > The reason is that task X could be runnable but not yet on CPU. The the > task performing the wakeup did not leave the CPU it could performe > multiple wakeups. > > With the proper timming task X could be running and enqueued for a > wakeup. If this happens while X is performing a fork() then its its > child will have a !NULL `wake_q` member copied. > > This is not a problem as long as the child task does not participate in > lockless wakeups :) > > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> > Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> > Cc: Davidlohr Bueso <dbueso@xxxxxxx> > Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Fixes: 7675104990ed ("sched: Implement lockless wake-queues") Shouldn't that go into stable? Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html