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SubjectRe: 2.6.-test10: bad "__might_sleep" in ALSA sound drivers
Hi,

At Mon, 24 Nov 2003 18:00:17 -0800,
Andrew Morton wrote:
>
> Torrey Hoffman <thoffman@arnor.net> 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@suse.de> 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;
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