X-Git-Url: http://ftp.carnet.hr/carnet-debian/scm?p=php5-apc.git;a=blobdiff_plain;f=pgsql_s_lock.c;fp=pgsql_s_lock.c;h=4b8b40a3476160e8242772bde72dc79a352e5404;hp=0000000000000000000000000000000000000000;hb=3682e0a7a26931aabca2b6e54eb08efd7dc0430b;hpb=575ce08215526bb71a967d69d601e77e1afbcd11 diff --git a/pgsql_s_lock.c b/pgsql_s_lock.c new file mode 100644 index 0000000..4b8b40a --- /dev/null +++ b/pgsql_s_lock.c @@ -0,0 +1,481 @@ +/* + +----------------------------------------------------------------------+ + | APC | + +----------------------------------------------------------------------+ + | Copyright (c) 2007 The PHP Group | + +----------------------------------------------------------------------+ + | This source file is subject to version 3.01 of the PHP license, | + | that is bundled with this package in the file LICENSE, and is | + | available through the world-wide-web at the following url: | + | http://www.php.net/license/3_01.txt | + | If you did not receive a copy of the PHP license and are unable to | + | obtain it through the world-wide-web, please send a note to | + | license@php.net so we can mail you a copy immediately. | + +----------------------------------------------------------------------+ + | The following code was ported from the PostgreSQL project, please | + | see appropriate copyright notices that follow. | + | Initial conversion by Brian Shire | + +----------------------------------------------------------------------+ + + */ + +/* $Id: pgsql_s_lock.c,v 3.2 2007/02/25 05:19:11 shire Exp $ */ + +/*------------------------------------------------------------------------- + * + * s_lock.c + * Hardware-dependent implementation of spinlocks. + * + * + * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group + * Portions Copyright (c) 1994, Regents of the University of California + * + * + * IDENTIFICATION + * $PostgreSQL: pgsql/src/backend/storage/lmgr/s_lock.c,v 1.47 2006/10/04 00:29:58 momjian Exp $ + * + *------------------------------------------------------------------------- + */ +/* #include "postgres.h" -- Removed for APC */ + +/* -- Added for APC -- */ +#include "apc.h" +#ifdef APC_SPIN_LOCKS + +#ifdef S_LOCK_TEST +#include +#endif +#ifndef WIN32 +#include +#endif +/* ---- */ + +#include +#include + +/* #include "storage/s_lock.h" -- Removed for APC */ +#include "pgsql_s_lock.h" + +static int spins_per_delay = DEFAULT_SPINS_PER_DELAY; + + +/* -- APC specific additions ------------------------------*/ +/* The following dependencies have been copied from + * other pgsql source files. The original locations + * have been noted. + */ + +/* -- from include/c.h -- */ +#ifndef TRUE +#define TRUE 1 +#endif + +#ifndef FALSE +#define FALSE 0 +#endif + +/* -- from include/pg_config_manual.h -- */ +#define MAX_RANDOM_VALUE (0x7FFFFFFF) + +/* + * Max + * Return the maximum of two numbers. + */ +#define Max(x, y) ((x) > (y) ? (x) : (y)) + +/* -- from include/c.h -- */ +/* + * Min + * Return the minimum of two numbers. + */ +#define Min(x, y) ((x) < (y) ? (x) : (y)) + + +/* -- from backend/port/win32/signal.c -- */ +/* + * pg_usleep --- delay the specified number of microseconds. + * + * NOTE: although the delay is specified in microseconds, the effective + * resolution is only 1/HZ, or 10 milliseconds, on most Unixen. Expect + * the requested delay to be rounded up to the next resolution boundary. + * + * On machines where "long" is 32 bits, the maximum delay is ~2000 seconds. + */ +void +pg_usleep(long microsec) +{ + if (microsec > 0) + { +#ifndef WIN32 + struct timeval delay; + + delay.tv_sec = microsec / 1000000L; + delay.tv_usec = microsec % 1000000L; + (void) select(0, NULL, NULL, NULL, &delay); +#else + SleepEx((microsec < 500 ? 1 : (microsec + 500) / 1000), FALSE); +#endif + } +} + +/* -- End APC specific additions ------------------------------*/ + + +/* + * s_lock_stuck() - complain about a stuck spinlock + */ +static void +s_lock_stuck(volatile slock_t *lock, const char *file, int line) +{ +#if defined(S_LOCK_TEST) + fprintf(stderr, + "\nStuck spinlock (%p) detected at %s:%d.\n", + lock, file, line); + exit(1); +#else + /* -- Removed for APC + elog(PANIC, "stuck spinlock (%p) detected at %s:%d", + lock, file, line); + */ + apc_eprint("Stuck spinlock (%p) detected", lock); +#endif +} + + +/* + * s_lock(lock) - platform-independent portion of waiting for a spinlock. + */ +void +s_lock(volatile slock_t *lock, const char *file, int line) +{ + /* + * We loop tightly for awhile, then delay using pg_usleep() 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 as an + * initial guess. However, on a uniprocessor the loop is a waste of + * cycles, while in a multi-CPU scenario it's usually better to spin a bit + * longer than to call the kernel, so we try to adapt the spin loop count + * depending on whether we seem to be in a uniprocessor or multiprocessor. + * + * Note: you might think MIN_SPINS_PER_DELAY should be just 1, but you'd + * be wrong; there are platforms where that can result in a "stuck + * spinlock" failure. This has been seen particularly on Alphas; it seems + * that the first TAS after returning from kernel space will always fail + * on that hardware. + * + * Once we do decide to block, we use randomly increasing pg_usleep() + * delays. The first delay is 1 msec, then the delay randomly increases to + * about one second, after which we reset to 1 msec and start again. The + * idea here is that in the presence of heavy contention we need to + * increase the delay, else the spinlock holder may never get to run and + * release the lock. (Consider situation where spinlock holder has been + * nice'd down in priority by the scheduler --- it will not get scheduled + * until all would-be acquirers are sleeping, so if we always use a 1-msec + * sleep, there is a real possibility of starvation.) But we can't just + * clamp the delay to an upper bound, else it would take a long time to + * make a reasonable number of tries. + * + * We time out and declare error after NUM_DELAYS delays (thus, exactly + * that many tries). With the given settings, this will usually take 2 or + * so minutes. It seems better to fix the total number of tries (and thus + * the probability of unintended failure) than to fix the total time + * spent. + * + * The pg_usleep() delays are measured in milliseconds because 1 msec is a + * common resolution limit at the OS level for newer platforms. On older + * platforms the resolution limit is usually 10 msec, in which case the + * total delay before timeout will be a bit more. + */ +#define MIN_SPINS_PER_DELAY 10 +#define MAX_SPINS_PER_DELAY 1000 +#define NUM_DELAYS 1000 +#define MIN_DELAY_MSEC 1 +#define MAX_DELAY_MSEC 1000 + + int spins = 0; + int delays = 0; + int cur_delay = 0; + + while (TAS(lock)) + { + /* CPU-specific delay each time through the loop */ + SPIN_DELAY(); + + /* Block the process every spins_per_delay tries */ + if (++spins >= spins_per_delay) + { + if (++delays > NUM_DELAYS) + s_lock_stuck(lock, file, line); + + if (cur_delay == 0) /* first time to delay? */ + cur_delay = MIN_DELAY_MSEC; + + pg_usleep(cur_delay * 1000L); + +#if defined(S_LOCK_TEST) + fprintf(stdout, "*"); + fflush(stdout); +#endif + + /* increase delay by a random fraction between 1X and 2X */ + cur_delay += (int) (cur_delay * + ((double) random() / (double) MAX_RANDOM_VALUE) + 0.5); + /* wrap back to minimum delay when max is exceeded */ + if (cur_delay > MAX_DELAY_MSEC) + cur_delay = MIN_DELAY_MSEC; + + spins = 0; + } + } + + /* + * If we were able to acquire the lock without delaying, it's a good + * indication we are in a multiprocessor. If we had to delay, it's a sign + * (but not a sure thing) that we are in a uniprocessor. Hence, we + * decrement spins_per_delay slowly when we had to delay, and increase it + * rapidly when we didn't. It's expected that spins_per_delay will + * converge to the minimum value on a uniprocessor and to the maximum + * value on a multiprocessor. + * + * Note: spins_per_delay is local within our current process. We want to + * average these observations across multiple backends, since it's + * relatively rare for this function to even get entered, and so a single + * backend might not live long enough to converge on a good value. That + * is handled by the two routines below. + */ + if (cur_delay == 0) + { + /* we never had to delay */ + if (spins_per_delay < MAX_SPINS_PER_DELAY) + spins_per_delay = Min(spins_per_delay + 100, MAX_SPINS_PER_DELAY); + } + else + { + if (spins_per_delay > MIN_SPINS_PER_DELAY) + spins_per_delay = Max(spins_per_delay - 1, MIN_SPINS_PER_DELAY); + } +} + + +#if 0 /* -- APC doesn't use the set_spins_per_delay or update_spins_per_delay -- */ +/* + * Set local copy of spins_per_delay during backend startup. + * + * NB: this has to be pretty fast as it is called while holding a spinlock + */ +void +set_spins_per_delay(int shared_spins_per_delay) +{ + spins_per_delay = shared_spins_per_delay; +} + +/* + * Update shared estimate of spins_per_delay during backend exit. + * + * NB: this has to be pretty fast as it is called while holding a spinlock + */ +int +update_spins_per_delay(int shared_spins_per_delay) +{ + /* + * We use an exponential moving average with a relatively slow adaption + * rate, so that noise in any one backend's result won't affect the shared + * value too much. As long as both inputs are within the allowed range, + * the result must be too, so we need not worry about clamping the result. + * + * We deliberately truncate rather than rounding; this is so that single + * adjustments inside a backend can affect the shared estimate (see the + * asymmetric adjustment rules above). + */ + return (shared_spins_per_delay * 15 + spins_per_delay) / 16; +} +#endif + +/* + * 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 you change something here, you will likely need to modify s_lock.h too, + * because the definitions for these are split between this file and s_lock.h. + */ + + +#ifdef HAVE_SPINLOCKS /* skip spinlocks if requested */ + + +#if defined(__GNUC__) + +/* + * All the gcc flavors that are not inlined + */ + + +/* + * Note: all the if-tests here probably ought to be testing gcc version + * rather than platform, but I don't have adequate info to know what to + * write. Ideally we'd flush all this in favor of the inline version. + */ +#if defined(__m68k__) && !defined(__linux__) +/* really means: extern int tas(slock_t* **lock); */ +static void +tas_dummy() +{ + __asm__ __volatile__( +#if defined(__NetBSD__) && defined(__ELF__) +/* no underscore for label and % for registers */ + "\ +.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" +#else + "\ +.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 /* __NetBSD__ && __ELF__ */ + ); +} +#endif /* __m68k__ && !__linux__ */ +#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 */ +#endif /* not __GNUC__ */ +#endif /* HAVE_SPINLOCKS */ + + + +/*****************************************************************************/ +#if defined(S_LOCK_TEST) + +/* + * test program for verifying a port's spinlock support. + */ + +struct test_lock_struct +{ + char pad1; + slock_t lock; + char pad2; +}; + +volatile struct test_lock_struct test_lock; + +int +main() +{ + srandom((unsigned int) time(NULL)); + + test_lock.pad1 = test_lock.pad2 = 0x44; + + S_INIT_LOCK(&test_lock.lock); + + if (test_lock.pad1 != 0x44 || test_lock.pad2 != 0x44) + { + printf("S_LOCK_TEST: failed, declared datatype is wrong size\n"); + return 1; + } + + if (!S_LOCK_FREE(&test_lock.lock)) + { + printf("S_LOCK_TEST: failed, lock not initialized\n"); + return 1; + } + + S_LOCK(&test_lock.lock); + + if (test_lock.pad1 != 0x44 || test_lock.pad2 != 0x44) + { + printf("S_LOCK_TEST: failed, declared datatype is wrong size\n"); + return 1; + } + + if (S_LOCK_FREE(&test_lock.lock)) + { + printf("S_LOCK_TEST: failed, lock not locked\n"); + return 1; + } + + S_UNLOCK(&test_lock.lock); + + if (test_lock.pad1 != 0x44 || test_lock.pad2 != 0x44) + { + printf("S_LOCK_TEST: failed, declared datatype is wrong size\n"); + return 1; + } + + if (!S_LOCK_FREE(&test_lock.lock)) + { + printf("S_LOCK_TEST: failed, lock not unlocked\n"); + return 1; + } + + S_LOCK(&test_lock.lock); + + if (test_lock.pad1 != 0x44 || test_lock.pad2 != 0x44) + { + printf("S_LOCK_TEST: failed, declared datatype is wrong size\n"); + return 1; + } + + if (S_LOCK_FREE(&test_lock.lock)) + { + printf("S_LOCK_TEST: failed, lock not re-locked\n"); + return 1; + } + + printf("S_LOCK_TEST: this will print %d stars and then\n", NUM_DELAYS); + printf(" exit with a 'stuck spinlock' message\n"); + printf(" if S_LOCK() and TAS() are working.\n"); + fflush(stdout); + + s_lock(&test_lock.lock, __FILE__, __LINE__); + + printf("S_LOCK_TEST: failed, lock not locked\n"); + return 1; +} + +#endif /* S_LOCK_TEST */ + +#endif /* APC_SPIN_LOCKS */