* Michal Piotrowski <[email protected]> wrote:
> I get this with Ingo's lockdep patch from
> http://people.redhat.com/mingo/generic-irq-subsystem/
sigh, that patchset is not released yet ... it showed up in the genirq
directory accidentally. (will release it later today)
> ====================================
> [ BUG: possible deadlock detected! ]
> ------------------------------------
at first sight this looks like a rare case of nested locking not yet
covered by the lock validator. Could you try the patch below, to
correctly express this locking construct to the lock validator?
Btw., beyond this false positive, i dont see how the lock ordering
between ports is guaranteed - maybe there's some implicit rule that
enforces it. And the whole grp->list_lock and grp->list_mutex lock use
seems quite fragile - using list_lock in atomic contexts and list_mutex
in schedulable contexts?
Ingo
Index: linux/sound/core/seq/seq_ports.c
===================================================================
--- linux.orig/sound/core/seq/seq_ports.c
+++ linux/sound/core/seq/seq_ports.c
@@ -518,7 +518,7 @@ int snd_seq_port_connect(struct snd_seq_
atomic_set(&subs->ref_count, 2);
down_write(&src->list_mutex);
- down_write(&dest->list_mutex);
+ down_write_nested(&dest->list_mutex, SINGLE_DEPTH_NESTING);
exclusive = info->flags & SNDRV_SEQ_PORT_SUBS_EXCLUSIVE ? 1 : 0;
err = -EBUSY;
@@ -591,7 +591,7 @@ int snd_seq_port_disconnect(struct snd_s
unsigned long flags;
down_write(&src->list_mutex);
- down_write(&dest->list_mutex);
+ down_write_nested(&dest->list_mutex, SINGLE_DEPTH_NESTING);
/* look for the connection */
list_for_each(p, &src->list_head) {
-
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