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Commit add659bf authored by Andi Kleen's avatar Andi Kleen Committed by Andi Kleen
Browse files

[PATCH] i386: Remove lock section support in rwsem.h 



Lock sections don't work the new dwarf2 unwinder
This generates slightly smaller code. It adds one more taken
jump to the fast path.

Also move the trampolines into semaphore.S and add proper CFI
annotations.

Cc: jbeulich@novell.com

Signed-off-by: default avatarAndi Kleen <ak@suse.de>
parent 01215ad8

arch/i386/lib/semaphore.S

+63 −0
Original line number Diff line number Diff line
@@ -152,3 +152,66 @@ ENTRY(__read_lock_failed) 
	END(__read_lock_failed)



#endif



/* Fix up special calling conventions */

ENTRY(call_rwsem_down_read_failed)

	CFI_STARTPROC

	push %ecx

	CFI_ADJUST_CFA_OFFSET 4

	CFI_REL_OFFSET ecx,0

	push %edx

	CFI_ADJUST_CFA_OFFSET 4

	CFI_REL_OFFSET edx,0

	call rwsem_down_read_failed

	pop %edx

	CFI_ADJUST_CFA_OFFSET -4

	pop %ecx

	CFI_ADJUST_CFA_OFFSET -4

	ret

	CFI_ENDPROC

	END(call_rwsem_down_read_failed)



ENTRY(call_rwsem_down_write_failed)

	CFI_STARTPROC

	push %ecx

	CFI_ADJUST_CFA_OFFSET 4

	CFI_REL_OFFSET ecx,0

	calll rwsem_down_write_failed

	pop %ecx

	CFI_ADJUST_CFA_OFFSET -4

	ret

	CFI_ENDPROC

	END(call_rwsem_down_write_failed)



ENTRY(call_rwsem_wake)

	CFI_STARTPROC

	decw %dx    /* do nothing if still outstanding active readers */

	jnz 1f

	push %ecx

	CFI_ADJUST_CFA_OFFSET 4

	CFI_REL_OFFSET ecx,0

	call rwsem_wake

	pop %ecx

	CFI_ADJUST_CFA_OFFSET -4

1:	ret

	CFI_ENDPROC

	END(call_rwsem_wake)



/* Fix up special calling conventions */

ENTRY(call_rwsem_downgrade_wake)

	CFI_STARTPROC

	push %ecx

	CFI_ADJUST_CFA_OFFSET 4

	CFI_REL_OFFSET ecx,0

	push %edx

	CFI_ADJUST_CFA_OFFSET 4

	CFI_REL_OFFSET edx,0

	call rwsem_downgrade_wake

	pop %edx

	CFI_ADJUST_CFA_OFFSET -4

	pop %ecx

	CFI_ADJUST_CFA_OFFSET -4

	ret

	CFI_ENDPROC

	END(call_rwsem_downgrade_wake)

include/asm-i386/rwsem.h

+12 −50
Original line number Diff line number Diff line
@@ -99,17 +99,9 @@ static inline void __down_read(struct rw_semaphore *sem) 
	__asm__ __volatile__(

		"# beginning down_read\n\t"

LOCK_PREFIX	"  incl      (%%eax)\n\t" /* adds 0x00000001, returns the old value */

		"  js        2f\n\t" /* jump if we weren't granted the lock */

		"  jns        1f\n"

		"  call call_rwsem_down_read_failed\n"

		"1:\n\t"

		LOCK_SECTION_START("")

		"2:\n\t"

		"  pushl     %%ecx\n\t"

		"  pushl     %%edx\n\t"

		"  call      rwsem_down_read_failed\n\t"

		"  popl      %%edx\n\t"

		"  popl      %%ecx\n\t"

		"  jmp       1b\n"

		LOCK_SECTION_END

		"# ending down_read\n\t"

		: "+m" (sem->count)

		: "a" (sem)
@@ -151,15 +143,9 @@ static inline void __down_write_nested(struct rw_semaphore *sem, int subclass) 
		"# beginning down_write\n\t"

LOCK_PREFIX	"  xadd      %%edx,(%%eax)\n\t" /* subtract 0x0000ffff, returns the old value */

		"  testl     %%edx,%%edx\n\t" /* was the count 0 before? */

		"  jnz       2f\n\t" /* jump if we weren't granted the lock */

		"1:\n\t"

		LOCK_SECTION_START("")

		"2:\n\t"

		"  pushl     %%ecx\n\t"

		"  call      rwsem_down_write_failed\n\t"

		"  popl      %%ecx\n\t"

		"  jmp       1b\n"

		LOCK_SECTION_END

		"  jz        1f\n"

		"  call call_rwsem_down_write_failed\n"

		"1:\n"

		"# ending down_write"

		: "+m" (sem->count), "=d" (tmp)

		: "a" (sem), "1" (tmp)
@@ -193,17 +179,9 @@ static inline void __up_read(struct rw_semaphore *sem) 
	__asm__ __volatile__(

		"# beginning __up_read\n\t"

LOCK_PREFIX	"  xadd      %%edx,(%%eax)\n\t" /* subtracts 1, returns the old value */

		"  js        2f\n\t" /* jump if the lock is being waited upon */

		"1:\n\t"

		LOCK_SECTION_START("")

		"2:\n\t"

		"  decw      %%dx\n\t" /* do nothing if still outstanding active readers */

		"  jnz       1b\n\t"

		"  pushl     %%ecx\n\t"

		"  call      rwsem_wake\n\t"

		"  popl      %%ecx\n\t"

		"  jmp       1b\n"

		LOCK_SECTION_END

		"  jns        1f\n\t"

		"  call call_rwsem_wake\n"

		"1:\n"

		"# ending __up_read\n"

		: "+m" (sem->count), "=d" (tmp)

		: "a" (sem), "1" (tmp)
@@ -219,17 +197,9 @@ static inline void __up_write(struct rw_semaphore *sem) 
		"# beginning __up_write\n\t"

		"  movl      %2,%%edx\n\t"

LOCK_PREFIX	"  xaddl     %%edx,(%%eax)\n\t" /* tries to transition 0xffff0001 -> 0x00000000 */

		"  jnz       2f\n\t" /* jump if the lock is being waited upon */

		"  jz       1f\n"

		"  call call_rwsem_wake\n"

		"1:\n\t"

		LOCK_SECTION_START("")

		"2:\n\t"

		"  decw      %%dx\n\t" /* did the active count reduce to 0? */

		"  jnz       1b\n\t" /* jump back if not */

		"  pushl     %%ecx\n\t"

		"  call      rwsem_wake\n\t"

		"  popl      %%ecx\n\t"

		"  jmp       1b\n"

		LOCK_SECTION_END

		"# ending __up_write\n"

		: "+m" (sem->count)

		: "a" (sem), "i" (-RWSEM_ACTIVE_WRITE_BIAS)
@@ -244,17 +214,9 @@ static inline void __downgrade_write(struct rw_semaphore *sem) 
	__asm__ __volatile__(

		"# beginning __downgrade_write\n\t"

LOCK_PREFIX	"  addl      %2,(%%eax)\n\t" /* transitions 0xZZZZ0001 -> 0xYYYY0001 */

		"  js        2f\n\t" /* jump if the lock is being waited upon */

		"  jns       1f\n\t"

		"  call call_rwsem_downgrade_wake\n"

		"1:\n\t"

		LOCK_SECTION_START("")

		"2:\n\t"

		"  pushl     %%ecx\n\t"

		"  pushl     %%edx\n\t"

		"  call      rwsem_downgrade_wake\n\t"

		"  popl      %%edx\n\t"

		"  popl      %%ecx\n\t"

		"  jmp       1b\n"

		LOCK_SECTION_END

		"# ending __downgrade_write\n"

		: "+m" (sem->count)

		: "a" (sem), "i" (-RWSEM_WAITING_BIAS)