Re: 2.6.-test10: bad "__might_sleep" in ALSA sound drivers

[Takashi Iwai]

Hi,

At Mon, 24 Nov 2003 18:00:17 -0800,
Andrew Morton wrote:
> 
> Torrey Hoffman <thoffman@xxxxxxxxx> wrote:
> >
> > I get this every time I boot 2.6.0-test10.  I think this problem has
> > been around for a while.
> > 
> > Debug: sleeping function called from invalid context at
> > include/asm/semaphore.h:119
> > in_atomic():1, irqs_disabled():0
> > Call Trace:
> >  [<c01229d0>] __might_sleep+0xab/0xc9
> >  [<fcff57bd>] ap_cs8427_sendbytes+0x38/0xd2 [snd_ice1712]
> >  [<fcfa825a>] snd_i2c_sendbytes+0x22/0x26 [snd_i2c]
> >  [<fcfaf15e>] snd_cs8427_reg_read+0x2c/0x8c [snd_cs8427]
> >  [<fcfaf414>] snd_cs8427_create+0xa4/0x347 [snd_cs8427]
> >  [<c02dc4b0>] snd_device_new+0x20/0x6a
> >  [<fcff151a>] snd_ice1712_init_cs8427+0x2f/0x6f [snd_ice1712]
> >  [<fcff6153>] snd_ice1712_delta_init+0x230/0x2b9 [snd_ice1712]
> >  [<fcff5227>] snd_ice1712_probe+0x323/0x34c [snd_ice1712]
> 
> snd_cs8427_create() does:
> 
> 	snd_i2c_lock(bus);
> 	if ((err = snd_cs8427_reg_read(device, CS8427_REG_ID_AND_VER)) != CS8427_VER8427A) {
> 
> the first statement takes a spinlock.  snd_cs8427_reg_read() then calls
> ap_cs8427_sendbytes() which downs a semaphore.
> 
> 
> It might be more appropriate to use a semaphore for ice1712_t.gpio_mutex?

the attached patch fixes this, simply replacing spinlock with mutex.
it's already in ALSA 1.0.0pre release.

--
Takashi Iwai <tiwai@xxxxxxx>		ALSA Developer - www.alsa-project.org
diff -ru linux/include/sound linux/include/sound
--- linux/include/sound/i2c.h	23 Apr 2002 13:20:58 -0000	1.3
+++ linux/include/sound/i2c.h	13 Nov 2003 11:18:12 -0000	1.4
@@ -58,7 +58,7 @@
 	snd_card_t *card;	/* card which I2C belongs to */
 	char name[32];		/* some useful label */
 
-	spinlock_t lock;
+	struct semaphore lock_mutex;
 
 	snd_i2c_bus_t *master;	/* master bus when SCK/SCL is shared */
 	struct list_head buses;	/* master: slave buses sharing SCK/SCL, slave: link list */
@@ -84,15 +84,15 @@
 
 static inline void snd_i2c_lock(snd_i2c_bus_t *bus) {
 	if (bus->master)
-		spin_lock(&bus->master->lock);
+		down(&bus->master->lock_mutex);
 	else
-		spin_lock(&bus->lock);
+		down(&bus->lock_mutex);
 }
 static inline void snd_i2c_unlock(snd_i2c_bus_t *bus) {
 	if (bus->master)
-		spin_unlock(&bus->master->lock);
+		up(&bus->master->lock_mutex);
 	else
-		spin_unlock(&bus->lock);
+		up(&bus->lock_mutex);
 }
 
 int snd_i2c_sendbytes(snd_i2c_device_t *device, unsigned char *bytes, int count);
diff -ru linux/sound linux/sound
--- linux/sound/i2c/i2c.c	2 Jun 2003 10:04:44 -0000	1.7
+++ linux/sound/i2c/i2c.c	13 Nov 2003 11:18:25 -0000	1.8
@@ -84,7 +84,7 @@
 	bus = (snd_i2c_bus_t *)snd_magic_kcalloc(snd_i2c_bus_t, 0, GFP_KERNEL);
 	if (bus == NULL)
 		return -ENOMEM;
-	spin_lock_init(&bus->lock);
+	init_MUTEX(&bus->lock_mutex);
 	INIT_LIST_HEAD(&bus->devices);
 	INIT_LIST_HEAD(&bus->buses);
 	bus->card = card;