From: Arjan van de Ven <arjan@infradead.org>
Date: Tue, 4 Jul 2006 10:07:22 +0000 (-0700)
Subject: [PATCH] fix AB-BA deadlock inversion at cs46xx_dsp_remove_scb
X-Git-Tag: v2.6.18-rc1~13
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c6482dde1c2811afba289b2344268f850595f350;p=pandora-kernel.git

[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>
---

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