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