Messages in this thread Patch in this message | | | Date | Wed, 02 Mar 2016 10:09:00 -0500 | From | Steven Rostedt <> | Subject | [PATCH RT 01/22] sched: reset tasks lockless wake-queues on fork() |
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4.1.15-rt18-rc1 stable review patch. If anyone has any objections, please let me know.
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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
In 7675104990ed ("sched: Implement lockless wake-queues") we gained lockless wake-queues. -RT 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 :)
Fixes: 7675104990ed ("sched: Implement lockless wake-queues") Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> --- kernel/fork.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/kernel/fork.c b/kernel/fork.c index 1b0e656f60e8..8f8a0a13d212 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -387,6 +387,7 @@ 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); -- 2.7.0
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