This is a note to let you know that I've just added the patch titled
ring-buffer: Check pending waiters when doing wake ups as well
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ring-buffer-check-pending-waiters-when-doing-wake-ups-as-well.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ec0bbc5ec5664dcee344f79373852117dc672c86 Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>
Date: Tue, 27 Sep 2022 19:15:25 -0400
Subject: ring-buffer: Check pending waiters when doing wake ups as well
From: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
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@xxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Fixes: 15693458c4bc0 ("tracing/ring-buffer: Move poll wake ups into ring buffer code")
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
@@ -513,8 +513,9 @@ 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);
}
}
Patches currently in stable-queue which might be from rostedt@xxxxxxxxxxx are
queue-4.9/ring-buffer-fix-race-between-reset-page-and-reading-page.patch
queue-4.9/ring-buffer-allow-splice-to-read-previous-partially-read-pages.patch
queue-4.9/ring-buffer-check-pending-waiters-when-doing-wake-ups-as-well.patch
