This is a note to let you know that I've just added the patch titled
ALSA: seq: Avoid invalid lockdep class warning
to the 3.18-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:
alsa-seq-avoid-invalid-lockdep-class-warning.patch
and it can be found in the queue-3.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 3510c7aa069aa83a2de6dab2b41401a198317bdc Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@xxxxxxx>
Date: Mon, 6 Nov 2017 20:16:50 +0100
Subject: ALSA: seq: Avoid invalid lockdep class warning
From: Takashi Iwai <tiwai@xxxxxxx>
commit 3510c7aa069aa83a2de6dab2b41401a198317bdc upstream.
The recent fix for adding rwsem nesting annotation was using the given
"hop" argument as the lock subclass key. Although the idea itself
works, it may trigger a kernel warning like:
BUG: looking up invalid subclass: 8
....
since the lockdep has a smaller number of subclasses (8) than we
currently allow for the hops there (10).
The current definition is merely a sanity check for avoiding the too
deep delivery paths, and the 8 hops are already enough. So, as a
quick fix, just follow the max hops as same as the max lockdep
subclasses.
Fixes: 1f20f9ff57ca ("ALSA: seq: Fix nested rwsem annotation for lockdep splat")
Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/sound/seq_kernel.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/include/sound/seq_kernel.h
+++ b/include/sound/seq_kernel.h
@@ -55,7 +55,8 @@ typedef union snd_seq_timestamp snd_seq_
#define SNDRV_SEQ_DEFAULT_CLIENT_EVENTS 200
/* max delivery path length */
-#define SNDRV_SEQ_MAX_HOPS 10
+/* NOTE: this shouldn't be greater than MAX_LOCKDEP_SUBCLASSES */
+#define SNDRV_SEQ_MAX_HOPS 8
/* max size of event size */
#define SNDRV_SEQ_MAX_EVENT_LEN 0x3fffffff
Patches currently in stable-queue which might be from tiwai@xxxxxxx are
queue-3.18/alsa-seq-avoid-invalid-lockdep-class-warning.patch
queue-3.18/alsa-seq-fix-oss-sysex-delivery-in-oss-emulation.patch