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Commit c6482dde authored by Arjan van de Ven's avatar Arjan van de Ven Committed by Linus Torvalds
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[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: default avatarArjan van de Ven <arjan@linux.intel.com>
Cc: Jaroslav Kysela <perex@suse.cz>
Acked-by: default avatarTakashi Iwai <tiwai@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent a46f9484

sound/pci/cs46xx/dsp_spos_scb_lib.c

+3 −2
Original line number Diff line number Diff line
@@ -180,6 +180,7 @@ static void _dsp_clear_sample_buffer (struct snd_cs46xx *chip, u32 sample_buffer 
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 @@ void cs46xx_dsp_remove_scb (struct snd_cs46xx *chip, struct dsp_scb_descriptor * 
		     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 );