pgsql_s_lock.c/h removed by accident

pgsql_s_lock.c

@@ -0,0 +1,391 @@
+/*
+  +----------------------------------------------------------------------+
+  | APC                                                                  |
+  +----------------------------------------------------------------------+
+  | Copyright (c) 2006-2011 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 307048 2011-01-03 23:53:17Z kalle $ */
+
+/*-------------------------------------------------------------------------
+ *
+ * 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_LOCK
+
+#ifdef S_LOCK_TEST
+#include <stdio.h>
+#endif
+#ifndef WIN32
+#include <sys/select.h>
+#endif
+/* ---- */
+
+#include <time.h>
+#ifdef WIN32
+#include "win32/unistd.h"
+#else
+#include <unistd.h>
+#endif
+
+/* #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 TSRMLS_DC)
+{
+#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_error("Stuck spinlock (%p) detected" TSRMLS_CC, 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 TSRMLS_DC)
+{
+	/*
+	 * 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 TSRMLS_CC);
+
+			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) rand() / (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 */
+
+#endif /* APC_SPIN_LOCKS */