ftrace may trigger rb_wakeups while holding pi_lock which will also be requested via trace_...->...->ring_buffer_unlock_commit->...-> irq_work_queue->raise_softirq->try_to_wake_up. This quickly causes deadlocks when trying to use ftrace under -rt. Resolve this by marking the ring buffer's irq_work as HARD_IRQ. Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx> --- I'm not yet sure if this doesn't push work into hard-irq context that is better not done there on -rt. I'm also not sure if there aren't more such cases, given that -rt turns the default irq_work wakeup policy around. But maybe we are lucky. kernel/trace/ring_buffer.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index f4fbbfc..6a1939e 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1252,6 +1252,7 @@ rb_allocate_cpu_buffer(struct ring_buffer *buffer, int nr_pages, int cpu) init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters); init_waitqueue_head(&cpu_buffer->irq_work.waiters); init_waitqueue_head(&cpu_buffer->irq_work.full_waiters); + cpu_buffer->irq_work.work.flags = IRQ_WORK_HARD_IRQ; bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), GFP_KERNEL, cpu_to_node(cpu)); -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
