/*------------------------------------------------------------------------- * * s_lock.c * Hardware-dependent implementation of spinlocks. * * * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION * $Header: /cvsroot/pgsql/src/backend/storage/lmgr/s_lock.c,v 1.11 2003/04/20 21:54:34 tgl Exp $ * *------------------------------------------------------------------------- */ #include "postgres.h" #include <sys/time.h> #include <unistd.h> #include "storage/s_lock.h" /* * s_lock_stuck() - complain about a stuck spinlock */ static void s_lock_stuck(volatile slock_t *lock, const char *file, int line) { fprintf(stderr, "\nFATAL: s_lock(%p) at %s:%d, stuck spinlock. Aborting.\n", lock, file, line); fprintf(stdout, "\nFATAL: s_lock(%p) at %s:%d, stuck spinlock. Aborting.\n", lock, file, line); abort(); } /* * s_lock(lock) - platform-independent portion of waiting for a spinlock. */ void s_lock(volatile slock_t *lock, const char *file, int line) { unsigned spins = 0; unsigned delays = 0; struct timeval delay; /* * We loop tightly for awhile, then delay using select() and try * again. Preferably, "awhile" should be a small multiple of the * maximum time we expect a spinlock to be held. 100 iterations seems * about right. * * We use a 10 millisec select delay because that is the lower limit on * many platforms. The timeout is figured on this delay only, and so * the nominal 1 minute is a lower bound. */ #define SPINS_PER_DELAY 100 #define DELAY_MSEC 10 #define TIMEOUT_MSEC (60 * 1000) while (TAS(lock)) { if (++spins > SPINS_PER_DELAY) { if (++delays > (TIMEOUT_MSEC / DELAY_MSEC)) s_lock_stuck(lock, file, line); delay.tv_sec = 0; delay.tv_usec = DELAY_MSEC * 1000; (void) select(0, NULL, NULL, NULL, &delay); spins = 0; } } } /* * Various TAS implementations that cannot live in s_lock.h as no inline * definition exists (yet). * In the future, get rid of tas.[cso] and fold it into this file. */ #if defined(__GNUC__) /************************************************************************* * All the gcc flavors that are not inlined */ #if defined(__m68k__) static void tas_dummy() /* really means: extern int tas(slock_t * **lock); */ { __asm__ __volatile__( "\ .global _tas \n\ _tas: \n\ movel sp@(0x4),a0 \n\ tas a0@ \n\ beq _success \n\ moveq #-128,d0 \n\ rts \n\ _success: \n\ moveq #0,d0 \n\ rts \n\ "); } #endif /* __m68k__ */ #if defined(__mips__) && !defined(__sgi) static void tas_dummy() { __asm__ __volatile__( "\ .global tas \n\ tas: \n\ .frame $sp, 0, $31 \n\ .set push \n\ .set mips2 \n\ ll $14, 0($4) \n\ or $15, $14, 1 \n\ sc $15, 0($4) \n\ .set pop \n\ beq $15, 0, fail\n\ bne $14, 0, fail\n\ li $2, 0 \n\ .livereg 0x2000FF0E,0x00000FFF \n\ j $31 \n\ fail: \n\ li $2, 1 \n\ j $31 \n\ "); } #endif /* __mips__ && !__sgi */ #else /* not __GNUC__ */ /*************************************************************************** * All non gcc */ #if defined(sun3) static void tas_dummy() /* really means: extern int tas(slock_t * *lock); */ { asm("LLA0:"); asm(" .data"); asm(" .text"); asm("|#PROC# 04"); asm(" .globl _tas"); asm("_tas:"); asm("|#PROLOGUE# 1"); asm(" movel sp@(0x4),a0"); asm(" tas a0@"); asm(" beq LLA1"); asm(" moveq #-128,d0"); asm(" rts"); asm("LLA1:"); asm(" moveq #0,d0"); asm(" rts"); asm(" .data"); } #endif /* sun3 */ #if defined(NEED_SPARC_TAS_ASM) /* * sparc machines not using gcc */ static void tas_dummy() /* really means: extern int tas(slock_t * *lock); */ { asm(".seg \"data\""); asm(".seg \"text\""); asm("_tas:"); /* * Sparc atomic test and set (sparc calls it "atomic load-store") */ asm("ldstub [%r8], %r8"); asm("retl"); asm("nop"); } #endif /* NEED_SPARC_TAS_ASM */ #if defined(NEED_I386_TAS_ASM) /* non gcc i386 based things */ #endif /* NEED_I386_TAS_ASM */ #endif /* not __GNUC__ */ /*****************************************************************************/ #if defined(S_LOCK_TEST) /* * test program for verifying a port. */ volatile slock_t test_lock; void main() { S_INIT_LOCK(&test_lock); if (!S_LOCK_FREE(&test_lock)) { printf("S_LOCK_TEST: failed, lock not initialized.\n"); exit(1); } S_LOCK(&test_lock); if (S_LOCK_FREE(&test_lock)) { printf("S_LOCK_TEST: failed, lock not locked\n"); exit(2); } printf("S_LOCK_TEST: this will hang for a few minutes and then abort\n"); printf(" with a 'stuck spinlock' message if S_LOCK()\n"); printf(" and TAS() are working.\n"); s_lock(&test_lock, __FILE__, __LINE__); printf("S_LOCK_TEST: failed, lock not locked~\n"); exit(3); } #endif /* S_LOCK_TEST */