[PATCH] fix AB-BA deadlock inversion at cs46xx_dsp_remove_scb
commitc6482dde1c2811afba289b2344268f850595f350
authorArjan van de Ven <arjan@infradead.org>
Tue, 4 Jul 2006 10:07:22 +0000 (4 03:07 -0700)
committerLinus Torvalds <torvalds@g5.osdl.org>
Tue, 4 Jul 2006 17:24:57 +0000 (4 10:24 -0700)
treebfd2ab0c2bcfe6fe4de64bab40f2c19f25131a97
parenta46f9484f8926aacb2e79a0e1676de3a6a6fbae8
[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>
sound/pci/cs46xx/dsp_spos_scb_lib.c