+++ /dev/null
-/*
- +----------------------------------------------------------------------+
- | APC |
- +----------------------------------------------------------------------+
- | Copyright (c) 2008 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 <shire@php.net> |
- +----------------------------------------------------------------------+
-
- */
-
-/* $Id: pgsql_s_lock.c,v 3.2.2.1 2008/05/11 18:57:00 rasmus 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 <stdio.h>
-#endif
-#ifndef WIN32
-#include <sys/select.h>
-#endif
-/* ---- */
-
-#include <time.h>
-#include <unistd.h>
-
-/* #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 */