[PATCH] fix AB-BA deadlock inversion at cs46xx_dsp_remove_scb
There is a code sequence where the locking is substream->self_group.lock
-> ins->scbs[index].lock
substream->self_group.lock is interrupt safe, and taken from irq context
as well (trace is snipped for brevity)
so what can happen is
cpu 0 cpu 1
user context user context
take ins->scbs[index].lock without disabling interrupts
get substream->self_group.lock (irqsafe)
try to get ins->scbs[index].lock (spins)
interrupt happens
try to get substream->self_group.lock (spins)
which is an obvious AB-BA deadlock
fix is to just take the lock with _irqsafe
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Jaroslav Kysela <perex@suse.cz>
Acked-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/sound/pci/cs46xx/dsp_spos_scb_lib.c b/sound/pci/cs46xx/dsp_spos_scb_lib.c
index 3844d18..232b337 100644
--- a/sound/pci/cs46xx/dsp_spos_scb_lib.c
+++ b/sound/pci/cs46xx/dsp_spos_scb_lib.c
@@ -180,6 +180,7 @@
void cs46xx_dsp_remove_scb (struct snd_cs46xx *chip, struct dsp_scb_descriptor * scb)
{
struct dsp_spos_instance * ins = chip->dsp_spos_instance;
+ unsigned long flags;
/* check integrety */
snd_assert ( (scb->index >= 0 &&
@@ -194,9 +195,9 @@
goto _end);
#endif
- spin_lock(&scb->lock);
+ spin_lock_irqsave(&scb->lock, flags);
_dsp_unlink_scb (chip,scb);
- spin_unlock(&scb->lock);
+ spin_unlock_irqrestore(&scb->lock, flags);
cs46xx_dsp_proc_free_scb_desc(scb);
snd_assert (scb->scb_symbol != NULL, return );