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[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: Andi Kleen <ak@suse.de>
This commit is contained in:
Andi Kleen 2006-09-26 10:52:31 +02:00 committed by Andi Kleen
parent 01215ad8d8
commit add659bf8a
2 changed files with 75 additions and 50 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

63
arch/i386/lib/semaphore.S
View File

@ -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)

62
include/asm-i386/rwsem.h
View File

@ -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)