linux-kernel - [PATCH 3.2 092/147] ALSA: seq: Enable 'use' locking in all configurations

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Message-ID: <lsq.1510009387.789141535@decadent.org.uk>
Date:   Mon, 06 Nov 2017 23:03:07 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Ben Hutchings" <ben.hutchings@...ethink.co.uk>,
        "Takashi Iwai" <tiwai@...e.de>
Subject: [PATCH 3.2 092/147] ALSA: seq: Enable 'use' locking in all
 configurations

3.2.95-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Ben Hutchings <ben.hutchings@...ethink.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@...ethink.co.uk>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 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 */