ring-buffer: Check pending waiters when doing wake ups as well

BugLink: https://bugs.launchpad.net/bugs/1996825
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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 07e274e769db8a24a297e50987a3b061e8f62c26..5613b5ea766e9dffce1c8b91a3b1f953507aebaf 100644 (file)
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -881,8 +881,9 @@ static void rb_wake_up_waiters(struct irq_work *work)
        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);
        }
 }