From: Stefan Richter <stefanr@s5r6.in-berlin.de>
Date: Thu, 19 Aug 2010 21:13:43 +0000 (-0700)
Subject: Documentation: kernel-locking: mutex_trylock cannot be used in interrupt context
X-Git-Tag: v2.6.36-rc2~14
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1ee41680572971e34d90d5f584daf33195ec6dcb;p=pandora-kernel.git

Documentation: kernel-locking: mutex_trylock cannot be used in interrupt context

Chapter 6 is right about mutex_trylock, but chapter 10 wasn't.  This error
was introduced during semaphore-to-mutex conversion of the Unreliable
guide.  :-)

If user context which performs mutex_lock() or mutex_trylock() is
preempted by interrupt context which performs mutex_trylock() on the same
mutex instance, a deadlock occurs.  This is because these functions do not
disable local IRQs when they operate on mutex->wait_lock.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

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