[PATCH for review] [81/145] i386: Remove lock section support in mutex.h, semaphore.h

From: Andi Kleen
Date: Thu Aug 10 2006 - 16:03:56 EST

r

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@xxxxxxxxxx

Signed-off-by: Andi Kleen <ak@xxxxxxx>

---
arch/i386/lib/semaphore.S | 63 +++++++++++++++++++++++++++++++++++++++++++
include/asm-i386/mutex.h | 16 ++--------
include/asm-i386/rwsem.h | 62 ++++++++----------------------------------
include/asm-i386/semaphore.h | 49 +++++++++++----------------------
4 files changed, 96 insertions(+), 94 deletions(-)

Index: linux/include/asm-i386/mutex.h
===================================================================
--- linux.orig/include/asm-i386/mutex.h
+++ linux/include/asm-i386/mutex.h
@@ -30,14 +30,10 @@ do { \
\
__asm__ __volatile__( \
LOCK_PREFIX " decl (%%eax) \n" \
- " js 2f \n" \
+ " jns 1f \n" \
+ " call "#fail_fn" \n" \
"1: \n" \
\
- LOCK_SECTION_START("") \
- "2: call "#fail_fn" \n" \
- " jmp 1b \n" \
- LOCK_SECTION_END \
- \
:"=a" (dummy) \
: "a" (count) \
: "memory", "ecx", "edx"); \
@@ -86,14 +82,10 @@ do { \
\
__asm__ __volatile__( \
LOCK_PREFIX " incl (%%eax) \n" \
- " jle 2f \n" \
+ " jg 1f \n" \
+ " call "#fail_fn" \n" \
"1: \n" \
\
- LOCK_SECTION_START("") \
- "2: call "#fail_fn" \n" \
- " jmp 1b \n" \
- LOCK_SECTION_END \
- \
:"=a" (dummy) \
: "a" (count) \
: "memory", "ecx", "edx"); \
Index: linux/arch/i386/lib/semaphore.S
===================================================================
--- linux.orig/arch/i386/lib/semaphore.S
+++ linux/arch/i386/lib/semaphore.S
@@ -130,3 +130,66 @@ 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_rwsemgrade_wake)
+
Index: linux/include/asm-i386/rwsem.h
===================================================================
--- linux.orig/include/asm-i386/rwsem.h
+++ linux/include/asm-i386/rwsem.h
@@ -99,17 +99,9 @@ static inline void __down_read(struct rw
__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(s
"# 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_s
__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_
"# 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(str
__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)
Index: linux/include/asm-i386/semaphore.h
===================================================================
--- linux.orig/include/asm-i386/semaphore.h
+++ linux/include/asm-i386/semaphore.h
@@ -100,13 +100,10 @@ static inline void down(struct semaphore
__asm__ __volatile__(
"# atomic down operation\n\t"
LOCK_PREFIX "decl %0\n\t" /* --sem->count */
- "js 2f\n"
- "1:\n"
- LOCK_SECTION_START("")
- "2:\tlea %0,%%eax\n\t"
- "call __down_failed\n\t"
- "jmp 1b\n"
- LOCK_SECTION_END
+ "jns 2f\n"
+ "\tlea %0,%%eax\n\t"
+ "call __down_failed\n"
+ "2:"
:"+m" (sem->count)
:
:"memory","ax");
@@ -123,15 +120,12 @@ static inline int down_interruptible(str
might_sleep();
__asm__ __volatile__(
"# atomic interruptible down operation\n\t"
+ "xorl %0,%0\n\t"
LOCK_PREFIX "decl %1\n\t" /* --sem->count */
- "js 2f\n\t"
- "xorl %0,%0\n"
- "1:\n"
- LOCK_SECTION_START("")
- "2:\tlea %1,%%eax\n\t"
- "call __down_failed_interruptible\n\t"
- "jmp 1b\n"
- LOCK_SECTION_END
+ "jns 2f\n\t"
+ "lea %1,%%eax\n\t"
+ "call __down_failed_interruptible\n"
+ "2:"
:"=a" (result), "+m" (sem->count)
:
:"memory");
@@ -148,15 +142,12 @@ static inline int down_trylock(struct se

__asm__ __volatile__(
"# atomic interruptible down operation\n\t"
+ "xorl %0,%0\n\t"
LOCK_PREFIX "decl %1\n\t" /* --sem->count */
- "js 2f\n\t"
- "xorl %0,%0\n"
- "1:\n"
- LOCK_SECTION_START("")
- "2:\tlea %1,%%eax\n\t"
+ "jns 2f\n\t"
+ "lea %1,%%eax\n\t"
"call __down_failed_trylock\n\t"
- "jmp 1b\n"
- LOCK_SECTION_END
+ "2:\n"
:"=a" (result), "+m" (sem->count)
:
:"memory");
@@ -166,22 +157,16 @@ static inline int down_trylock(struct se
/*
* Note! This is subtle. We jump to wake people up only if
* the semaphore was negative (== somebody was waiting on it).
- * The default case (no contention) will result in NO
- * jumps for both down() and up().
*/
static inline void up(struct semaphore * sem)
{
__asm__ __volatile__(
"# atomic up operation\n\t"
LOCK_PREFIX "incl %0\n\t" /* ++sem->count */
- "jle 2f\n"
- "1:\n"
- LOCK_SECTION_START("")
- "2:\tlea %0,%%eax\n\t"
- "call __up_wakeup\n\t"
- "jmp 1b\n"
- LOCK_SECTION_END
- ".subsection 0\n"
+ "jg 1f\n\t"
+ "lea %0,%%eax\n\t"
+ "call __up_wakeup\n"
+ "1:"
:"+m" (sem->count)
:
:"memory","ax");
-
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