--- /dev/null
+/*
+ +----------------------------------------------------------------------+
+ | 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 <shire@php.net> |
+ +----------------------------------------------------------------------+
+
+ */
+
+/* $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 <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 */
projects / php5-apc.git / blobdiff