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Commit 73165b88 authored by Ingo Molnar's avatar Ingo Molnar Committed by Linus Torvalds
Browse files

[PATCH] fix i386 mutex fastpath on FRAME_POINTER && !DEBUG_MUTEXES 



Call the mutex slowpath more conservatively - e.g.  FRAME_POINTERS can
change the calling convention, in which case a direct branch to the
slowpath becomes illegal.  Bug found by Hugh Dickins.

Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 042c904c

include/asm-i386/mutex.h

+14 −2
Original line number Diff line number Diff line
@@ -28,7 +28,13 @@ do { \ 
									\

	__asm__ __volatile__(						\

		LOCK	"   decl (%%eax)	\n"			\

			"   js "#fail_fn"	\n"			\

			"   js 2f		\n"			\

			"1:			\n"			\

									\

		LOCK_SECTION_START("")					\

			"2: call "#fail_fn"	\n"			\

			"   jmp 1b		\n"			\

		LOCK_SECTION_END					\

									\

		:"=a" (dummy)						\

		: "a" (count)						\
@@ -78,7 +84,13 @@ do { \ 
									\

	__asm__ __volatile__(						\

		LOCK	"   incl (%%eax)	\n"			\

			"   jle "#fail_fn"	\n"			\

			"   jle 2f		\n"			\

			"1:			\n"			\

									\

		LOCK_SECTION_START("")					\

			"2: call "#fail_fn"	\n"			\

			"   jmp 1b		\n"			\

		LOCK_SECTION_END					\

									\

		:"=a" (dummy)						\

		: "a" (count)						\

kernel/mutex.c

+0 −9
Original line number Diff line number Diff line
@@ -84,12 +84,6 @@ void fastcall __sched mutex_lock(struct mutex *lock) 
	/*

	 * The locking fastpath is the 1->0 transition from

	 * 'unlocked' into 'locked' state.

	 *

	 * NOTE: if asm/mutex.h is included, then some architectures

	 * rely on mutex_lock() having _no other code_ here but this

	 * fastpath. That allows the assembly fastpath to do

	 * tail-merging optimizations. (If you want to put testcode

	 * here, do it under #ifndef CONFIG_MUTEX_DEBUG.)

	 */

	__mutex_fastpath_lock(&lock->count, __mutex_lock_slowpath);

}
@@ -115,8 +109,6 @@ void fastcall __sched mutex_unlock(struct mutex *lock) 
	/*

	 * The unlocking fastpath is the 0->1 transition from 'locked'

	 * into 'unlocked' state:

	 *

	 * NOTE: no other code must be here - see mutex_lock() .

	 */

	__mutex_fastpath_unlock(&lock->count, __mutex_unlock_slowpath);

}
@@ -261,7 +253,6 @@ __mutex_lock_interruptible_slowpath(atomic_t *lock_count __IP_DECL__); 
 */

int fastcall __sched mutex_lock_interruptible(struct mutex *lock)

{

	/* NOTE: no other code must be here - see mutex_lock() */

	return __mutex_fastpath_lock_retval

			(&lock->count, __mutex_lock_interruptible_slowpath);

}