Patch "ALSA: seq: Enable 'use' locking in all configurations" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    ALSA: seq: Enable 'use' locking in all configurations

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-enable-use-locking-in-all-configurations.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 <stable@vger.kernel.org> know about it.


>From 8009d506a1dd00cf436b0c4cca0dcec130580a21 Mon Sep 17 00:00:00 2001
From: Ben Hutchings <ben.hutchings@codethink.co.uk>
Date: Wed, 18 Oct 2017 00:45:49 +0100
Subject: ALSA: seq: Enable 'use' locking in all configurations

From: Ben Hutchings <ben.hutchings@codethink.co.uk>

commit 8009d506a1dd00cf436b0c4cca0dcec130580a21 upstream.

The 'use' locking macros are no-ops if neither SMP or SND_DEBUG is
enabled.  This might once have been OK in non-preemptible
configurations, but even in that case snd_seq_read() may sleep while
relying on a 'use' lock.  So always use the proper implementations.

Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 sound/core/seq/seq_lock.c |    4 ----
 sound/core/seq/seq_lock.h |   12 ------------
 2 files changed, 16 deletions(-)

--- a/sound/core/seq/seq_lock.c
+++ b/sound/core/seq/seq_lock.c
@@ -23,8 +23,6 @@
 #include <sound/core.h>
 #include "seq_lock.h"
 
-#if defined(CONFIG_SMP) || defined(CONFIG_SND_DEBUG)
-
 /* wait until all locks are released */
 void snd_use_lock_sync_helper(snd_use_lock_t *lockp, const char *file, int line)
 {
@@ -42,5 +40,3 @@ void snd_use_lock_sync_helper(snd_use_lo
 }
 
 EXPORT_SYMBOL(snd_use_lock_sync_helper);
-
-#endif
--- a/sound/core/seq/seq_lock.h
+++ b/sound/core/seq/seq_lock.h
@@ -3,8 +3,6 @@
 
 #include <linux/sched.h>
 
-#if defined(CONFIG_SMP) || defined(CONFIG_SND_DEBUG)
-
 typedef atomic_t snd_use_lock_t;
 
 /* initialize lock */
@@ -20,14 +18,4 @@ typedef atomic_t snd_use_lock_t;
 void snd_use_lock_sync_helper(snd_use_lock_t *lock, const char *file, int line);
 #define snd_use_lock_sync(lockp) snd_use_lock_sync_helper(lockp, __BASE_FILE__, __LINE__)
 
-#else /* SMP || CONFIG_SND_DEBUG */
-
-typedef spinlock_t snd_use_lock_t;	/* dummy */
-#define snd_use_lock_init(lockp) /**/
-#define snd_use_lock_use(lockp) /**/
-#define snd_use_lock_free(lockp) /**/
-#define snd_use_lock_sync(lockp) /**/
-
-#endif /* SMP || CONFIG_SND_DEBUG */
-
 #endif /* __SND_SEQ_LOCK_H */


Patches currently in stable-queue which might be from ben.hutchings@codethink.co.uk are

queue-4.4/alsa-seq-enable-use-locking-in-all-configurations.patch