[PATCH 5.19 142/717] ring-buffer: Check pending waiters when doing wake ups as well

Greg Kroah-Hartman
2022-10-22T08:08:23Z

From: Steven Rostedt (Google) <rostedt@goodmis.org>

commit ec0bbc5ec5664dcee344f79373852117dc672c86 upstream.

The wake up waiters only checks the "wakeup_full" variable and not the
"full_waiters_pending". The full_waiters_pending is set when a waiter is
added to the wait queue. The wakeup_full is only set when an event is
triggered, and it clears the full_waiters_pending to avoid multiple calls
to irq_work_queue().

The irq_work callback really needs to check both wakeup_full as well as
full_waiters_pending such that this code can be used to wake up waiters
when a file is closed that represents the ring buffer and the waiters need
to be woken up.

Link: https://lkml.kernel.org/r/20220927231824.209460321@goodmis.org

Cc: stable@vger.kernel.org
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes: 15693458c4bc0 ("tracing/ring-buffer: Move poll wake ups into ring buffer code")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/trace/ring_buffer.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -917,8 +917,9 @@ static void rb_wake_up_waiters(struct ir
struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);

wake_up_all(&rbwork->waiters);
- if (rbwork->wakeup_full) {
+ if (rbwork->full_waiters_pending || rbwork->wakeup_full) {
rbwork->wakeup_full = false;
+ rbwork->full_waiters_pending = false;
wake_up_all(&rbwork->full_waiters);
}
}