Patch "ALSA: seq: Avoid invalid lockdep class warning" has been added to the 4.4-stable tree

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 4.4-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-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Takashi Iwai <[email protected]>
Date: Mon, 6 Nov 2017 20:16:50 +0100
Subject: ALSA: seq: Avoid invalid lockdep class warning

From: Takashi Iwai <[email protected]>

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.

---
 include/sound/seq_kernel.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

@@ -49,7 +49,8 @@ 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 [email protected] are

queue-4.4/alsa-seq-avoid-invalid-lockdep-class-warning.patch queue-4.4/alsa-seq-fix-oss-sysex-delivery-in-oss-emulation.patch