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    Subject[PATCH 5.10 075/390] ring-buffer: Check pending waiters when doing wake ups as well
    Date
    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
    @@ -794,8 +794,9 @@ 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);
    }
    }

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