Re: BUG: possible deadlock detected! (sound) [Was: 2.6.17-rc5-mm1]

Jiri Slaby
2006-05-30T13:09:09Z

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Arjan van de Ven napsal(a):
> On Tue, 2006-05-30 at 14:44 +0200, Takashi Iwai wrote:
>> This ops is a unique object assigned to a different "id" string.
>>
>> The first snd_seq_device_register_driver() called from emu10k1_synth.c
>> is the registration for the id "snd-synth-emu10k1".
>> Then in init_device(), the corresponding devices are initialized, and
>> one callback registers again another device for OSS sequencer with a
>> different id "snd-seq-oss" via snd_seq_device_new() inside the lock.
>> Now it hits the lock-detector but the lock should belong to a
>> different ops object in practice.
>>
>> This nested lock may happen only in two drivers, emu10k1-synth and
>> opl3, and only together with OSS emulation. Since the OSS emulation
>> layer don't do active registration from itself, no deadlock should
>> happen (in theory -- I may oversee something :)
>
> ok fair enough
>
> Jiri, can you test the patch below? (I don't have this hardware)
Sure, but the day after tomorrow, I am going away from that machine now.
>
> The ops structure has complex locking rules, where not all ops are
> equal, some are subordinate on others for some complex sound cards. This
> requires for lockdep checking that each individual reg_mutex is
> considered in separation for its locking rules.
>
> Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
>
> ---
> sound/core/seq/seq_device.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> Index: linux-2.6.17-rc4-mm3-lockdep/sound/core/seq/seq_device.c
> ===================================================================
> --- linux-2.6.17-rc4-mm3-lockdep.orig/sound/core/seq/seq_device.c
> +++ linux-2.6.17-rc4-mm3-lockdep/sound/core/seq/seq_device.c
> @@ -46,6 +46,7 @@
> #include <linux/kmod.h>
> #include <linux/slab.h>
> #include <linux/mutex.h>
> +#include <linux/lockdep.h>
>
> MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>");
> MODULE_DESCRIPTION("ALSA sequencer device management");
> @@ -73,6 +74,8 @@ struct ops_list {
> struct mutex reg_mutex;
>
> struct list_head list; /* next driver */
> +
> + struct lockdep_type_key reg_mutex_key;
> };
>
>
> @@ -379,7 +382,7 @@ static struct ops_list * create_driver(c
>
> /* set up driver entry */
> strlcpy(ops->id, id, sizeof(ops->id));
> - mutex_init(&ops->reg_mutex);
> + mutex_init_key(&ops->reg_mutex, id, &ops->reg_mutex_key);
> ops->driver = DRIVER_EMPTY;
> INIT_LIST_HEAD(&ops->dev_list);
> /* lock this instance */
>
>

- --
Jiri Slaby www.fi.muni.cz/~xslaby
\_.-^-._ jirislaby@gmail.com _.-^-._/
B67499670407CE62ACC8 22A032CC55C339D47A7E
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.3 (GNU/Linux)
Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org

iD8DBQFEfEQAMsxVwznUen4RAkp4AJwOMUsBK4kvE54X/oxcdcIWad8oGACghO2a
mZLtPAHamNSDsiNa1gOfgoE=
=CaIp
-----END PGP SIGNATURE-----