4.1.15-rt18-rc1 stable review patch. If anyone has any objections, please let me know. ------------------ From: Sebastian Andrzej Siewior 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 Signed-off-by: Steven Rostedt --- 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