Messages in this thread Patch in this message | | | Date | Wed, 6 Jan 2016 10:48:37 -0800 | From | tip-bot for Sebastian Andrzej Siewior <> | Subject | [tip:sched/core] sched/core: Reset task' s lockless wake-queues on fork() |
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Commit-ID: 093e5840ae76f1082633503964d035f40ed0216d Gitweb: http://git.kernel.org/tip/093e5840ae76f1082633503964d035f40ed0216d Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de> AuthorDate: Mon, 21 Dec 2015 18:17:10 +0100 Committer: Ingo Molnar <mingo@kernel.org> 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@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Davidlohr Bueso <dbueso@suse.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: 7675104990ed ("sched: Implement lockless wake-queues") Link: http://lkml.kernel.org/r/20151221171710.GA5499@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org> --- kernel/fork.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/kernel/fork.c b/kernel/fork.c index fce002e..1155eac 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -380,6 +380,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig) #endif tsk->splice_pipe = NULL; tsk->task_frag.page = NULL; + tsk->wake_q.next = NULL; account_kernel_stack(ti, 1);
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