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Adjust TAS assembly as per recent discussions: use "+m"(*lock) everywhere

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to reference the spinlock variable, and specify "memory" as a clobber
operand to be sure gcc does not try to keep shared-memory values in
registers across a spinlock acquisition.  Also tighten the S/390 asm
sequence, which was apparently written with only minimal study of the
gcc asm documentation.  I have personally tested i386, ia64, ppc, hppa,
and s390 variants --- there is some small chance that I broke the others,
but I doubt it.
This commit is contained in:
Tom Lane
2004-06-19 23:02:32 +00:00
parent c1d9dec3e3
commit 1098677482
1 changed files with 79 additions and 101 deletions
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178
src/include/storage/s_lock.h
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@@ -66,7 +66,7 @@
* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California * Portions Copyright (c) 1994, Regents of the University of California
* *
* $PostgreSQL: pgsql/src/include/storage/s_lock.h,v 1.125 2004/01/03 05:47:44 tgl Exp $ * $PostgreSQL: pgsql/src/include/storage/s_lock.h,v 1.126 2004/06/19 23:02:32 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@@ -85,16 +85,26 @@
* Other compilers use __cpu or __cpu__ so we test for both in those cases. * Other compilers use __cpu or __cpu__ so we test for both in those cases.
*/ */
/* /*----------
* Standard gcc asm format is: * Standard gcc asm format (assuming "volatile slock_t *lock"):
*
__asm__ __volatile__( __asm__ __volatile__(
" command \n" " instruction \n"
" command \n" " instruction \n"
" command \n" " instruction \n"
: "=r"(_res) return value, in register : "=r"(_res), "+m"(*lock) // return register, in/out lock value
: "r"(lock) argument, 'lock pointer', in register : "r"(lock) // lock pointer, in input register
: "r0"); inline code uses this register : "memory", "cc"); // show clobbered registers here
* The output-operands list (after first colon) should always include
* "+m"(*lock), whether or not the asm code actually refers to this
* operand directly. This ensures that gcc believes the value in the
* lock variable is used and set by the asm code. Also, the clobbers
* list (after third colon) should always include "memory"; this prevents
* gcc from thinking it can cache the values of shared-memory fields
* across the asm code. Add "cc" if your asm code changes the condition
* code register, and also list any temp registers the code uses.
*----------
*/ */
@@ -117,8 +127,9 @@ tas(volatile slock_t *lock)
" lock \n" " lock \n"
" xchgb %0,%1 \n" " xchgb %0,%1 \n"
"1: \n" "1: \n"
: "=q"(_res), "=m"(*lock) : "+q"(_res), "+m"(*lock)
: "0"(_res)); :
: "memory", "cc");
return (int) _res; return (int) _res;
} }
@@ -128,8 +139,7 @@ static __inline__ void
spin_delay(void) spin_delay(void)
{ {
__asm__ __volatile__( __asm__ __volatile__(
" rep; nop \n" " rep; nop \n");
: : : "memory");
} }
#endif /* __i386__ || __x86_64__ */ #endif /* __i386__ || __x86_64__ */
@@ -150,10 +160,9 @@ tas(volatile slock_t *lock)
__asm__ __volatile__( __asm__ __volatile__(
" xchg4 %0=%1,%2 \n" " xchg4 %0=%1,%2 \n"
: "=r"(ret), "=m"(*lock) : "=r"(ret), "+m"(*lock)
: "r"(1), "1"(*lock) : "r"(1)
: "memory"); : "memory");
return (int) ret; return (int) ret;
} }
@@ -173,17 +182,18 @@ tas(volatile slock_t *lock)
register slock_t _res = 1; register slock_t _res = 1;
__asm__ __volatile__( __asm__ __volatile__(
" swpb %0, %0, [%3] \n" " swpb %0, %0, [%2] \n"
: "=r"(_res), "=m"(*lock) : "+r"(_res), "+m"(*lock)
: "0"(_res), "r"(lock)); : "r"(lock)
: "memory");
return (int) _res; return (int) _res;
} }
#endif /* __arm__ */ #endif /* __arm__ */
#if defined(__s390__) && !defined(__s390x__) #if defined(__s390__) || defined(__s390x__)
/* S/390 Linux */ /* S/390 and S/390x Linux (32- and 64-bit zSeries) */
#define HAS_TEST_AND_SET #define HAS_TEST_AND_SET
typedef unsigned int slock_t; typedef unsigned int slock_t;
@@ -193,51 +203,17 @@ typedef unsigned int slock_t;
static __inline__ int static __inline__ int
tas(volatile slock_t *lock) tas(volatile slock_t *lock)
{ {
int _res; int _res = 0;
__asm__ __volatile__( __asm__ __volatile__(
" la 1,1 \n" " cs %0,%3,0(%2) \n"
" l 2,%2 \n" : "+d"(_res), "+m"(*lock)
" slr 0,0 \n" : "a"(lock), "d"(1)
" cs 0,1,0(2) \n" : "memory", "cc");
" lr %1,0 \n" return _res;
: "=m"(lock), "=d"(_res)
: "m"(lock)
: "0", "1", "2");
return (_res);
} }
#endif /* __s390__ */ #endif /* __s390__ || __s390x__ */
#if defined(__s390x__)
/* S/390x Linux (64-bit zSeries) */
#define HAS_TEST_AND_SET
typedef unsigned int slock_t;
#define TAS(lock) tas(lock)
static __inline__ int
tas(volatile slock_t *lock)
{
int _res;
__asm__ __volatile__(
" la 1,1 \n"
" lg 2,%2 \n"
" slr 0,0 \n"
" cs 0,1,0(2) \n"
" lr %1,0 \n"
: "=m"(lock), "=d"(_res)
: "m"(lock)
: "0", "1", "2");
return (_res);
}
#endif /* __s390x__ */
#if defined(__sparc__) #if defined(__sparc__)
@@ -250,12 +226,13 @@ typedef unsigned char slock_t;
static __inline__ int static __inline__ int
tas(volatile slock_t *lock) tas(volatile slock_t *lock)
{ {
register slock_t _res = 1; register slock_t _res;
__asm__ __volatile__( __asm__ __volatile__(
" ldstub [%2], %0 \n" " ldstub [%2], %0 \n"
: "=r"(_res), "=m"(*lock) : "=r"(_res), "+m"(*lock)
: "r"(lock)); : "r"(lock)
: "memory");
return (int) _res; return (int) _res;
} }
@@ -283,11 +260,11 @@ tas(volatile slock_t *lock)
int _res; int _res;
__asm__ __volatile__( __asm__ __volatile__(
" lwarx %0,0,%2 \n" " lwarx %0,0,%3 \n"
" cmpwi %0,0 \n" " cmpwi %0,0 \n"
" bne 1f \n" " bne 1f \n"
" addi %0,%0,1 \n" " addi %0,%0,1 \n"
" stwcx. %0,0,%2 \n" " stwcx. %0,0,%3 \n"
" beq 2f \n" " beq 2f \n"
"1: li %1,1 \n" "1: li %1,1 \n"
" b 3f \n" " b 3f \n"
@@ -296,10 +273,9 @@ tas(volatile slock_t *lock)
" li %1,0 \n" " li %1,0 \n"
"3: \n" "3: \n"
: "=&r" (_t), "=r" (_res) : "=&r"(_t), "=r"(_res), "+m"(*lock)
: "r"(lock) : "r"(lock)
: "cc", "memory" : "memory", "cc");
);
return _res; return _res;
} }
@@ -330,10 +306,9 @@ tas(volatile slock_t *lock)
" clrl %0 \n" " clrl %0 \n"
" tas %1 \n" " tas %1 \n"
" sne %0 \n" " sne %0 \n"
: "=d"(rv), "=m"(*lock) : "=d"(rv), "+m"(*lock)
: "1"(*lock) :
: "cc"); : "memory", "cc");
return rv; return rv;
} }
@@ -357,13 +332,13 @@ tas(volatile slock_t *lock)
register int _res; register int _res;
__asm__ __volatile__( __asm__ __volatile__(
" movl $1, r0 \n" " movl $1, %0 \n"
" bbssi $0, (%1), 1f \n" " bbssi $0, (%2), 1f \n"
" clrl r0 \n" " clrl %0 \n"
"1: movl r0, %0 \n" "1: \n"
: "=r"(_res) : "=&r"(_res), "+m"(*lock)
: "r"(lock) : "r"(lock)
: "r0"); : "memory");
return _res; return _res;
} }
@@ -383,9 +358,11 @@ tas(volatile slock_t *lock)
register int _res; register int _res;
__asm__ __volatile__( __asm__ __volatile__(
" sbitb 0, %0 \n" " sbitb 0, %1 \n"
" sfsd %1 \n" " sfsd %0 \n"
: "=m"(*lock), "=r"(_res)); : "=r"(_res), "+m"(*lock)
:
: "memory");
return _res; return _res;
} }
@@ -404,12 +381,6 @@ tas(volatile slock_t *lock)
typedef unsigned long slock_t; typedef unsigned long slock_t;
#define TAS(lock) tas(lock) #define TAS(lock) tas(lock)
#define S_UNLOCK(lock) \
do \
{\
__asm__ __volatile__ (" mb \n"); \
*((volatile slock_t *) (lock)) = 0; \
} while (0)
static __inline__ int static __inline__ int
tas(volatile slock_t *lock) tas(volatile slock_t *lock)
@@ -417,24 +388,30 @@ tas(volatile slock_t *lock)
register slock_t _res; register slock_t _res;
__asm__ __volatile__( __asm__ __volatile__(
" ldq $0, %0 \n" " ldq $0, %1 \n"
" bne $0, 2f \n" " bne $0, 2f \n"
" ldq_l %1, %0 \n" " ldq_l %0, %1 \n"
" bne %1, 2f \n" " bne %0, 2f \n"
" mov 1, $0 \n" " mov 1, $0 \n"
" stq_c $0, %0 \n" " stq_c $0, %1 \n"
" beq $0, 2f \n" " beq $0, 2f \n"
" mb \n" " mb \n"
" br 3f \n" " br 3f \n"
"2: mov 1, %1 \n" "2: mov 1, %0 \n"
"3: \n" "3: \n"
: "=m"(*lock), "=r"(_res) : "=&r"(_res), "+m"(*lock)
: :
: "0"); : "memory", "0");
return (int) _res; return (int) _res;
} }
#define S_UNLOCK(lock) \
do \
{\
__asm__ __volatile__ (" mb \n"); \
*((volatile slock_t *) (lock)) = 0; \
} while (0)
#endif /* __alpha || __alpha__ */ #endif /* __alpha || __alpha__ */
@@ -540,8 +517,9 @@ tas(volatile slock_t *lock)
__asm__ __volatile__( __asm__ __volatile__(
" ldcwx 0(0,%2),%0 \n" " ldcwx 0(0,%2),%0 \n"
: "=r"(lockval), "=m"(*lockword) : "=r"(lockval), "+m"(*lockword)
: "r"(lockword)); : "r"(lockword)
: "memory");
return (lockval == 0); return (lockval == 0);
} }