* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.45 2000/12/28 13:00:08 vadim Exp $
+ * $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.46 2000/12/29 21:31:21 tgl Exp $
*
*-------------------------------------------------------------------------
*/
}
}
}
- s_lock_sleep(i++);
+ S_LOCK_SLEEP(&(XLogCtl->insert_lck), i++);
if (!TAS(&(XLogCtl->insert_lck)))
break;
}
if (updrqst)
{
- for (;;)
- {
- if (!TAS(&(XLogCtl->info_lck)))
- {
- if (XLByteLT(XLogCtl->LgwrRqst.Write, LgwrRqst.Write))
- XLogCtl->LgwrRqst.Write = LgwrRqst.Write;
- S_UNLOCK(&(XLogCtl->info_lck));
- break;
- }
- s_lock_sleep(i++);
- }
+ S_LOCK(&(XLogCtl->info_lck));
+ if (XLByteLT(XLogCtl->LgwrRqst.Write, LgwrRqst.Write))
+ XLogCtl->LgwrRqst.Write = LgwrRqst.Write;
+ S_UNLOCK(&(XLogCtl->info_lck));
}
END_CRIT_CODE;
XLogRecPtr WriteRqst;
char buffer[BLCKSZ];
char *usebuf = NULL;
- unsigned i = 0;
+ unsigned spins = 0;
bool force_lgwr = false;
if (XLOG_DEBUG)
break;
}
}
- s_lock_sleep(i++);
+ S_LOCK_SLEEP(&(XLogCtl->lgwr_lck), spins++);
}
if (logFile >= 0 && (LgwrResult.Write.xlogid != logId ||
logId, logSeg);
LgwrResult.Flush = LgwrResult.Write;
- for (i = 0;;)
- {
- if (!TAS(&(XLogCtl->info_lck)))
- {
- XLogCtl->LgwrResult = LgwrResult;
- if (XLByteLT(XLogCtl->LgwrRqst.Write, LgwrResult.Write))
- XLogCtl->LgwrRqst.Write = LgwrResult.Write;
- S_UNLOCK(&(XLogCtl->info_lck));
- break;
- }
- s_lock_sleep(i++);
- }
+ S_LOCK(&(XLogCtl->info_lck));
+ XLogCtl->LgwrResult = LgwrResult;
+ if (XLByteLT(XLogCtl->LgwrRqst.Write, LgwrResult.Write))
+ XLogCtl->LgwrRqst.Write = LgwrResult.Write;
+ S_UNLOCK(&(XLogCtl->info_lck));
+
XLogCtl->Write.LgwrResult = LgwrResult;
S_UNLOCK(&(XLogCtl->lgwr_lck));
XLogCtlInsert *Insert = &XLogCtl->Insert;
XLogCtlWrite *Write = &XLogCtl->Write;
uint16 curridx = NextBufIdx(Insert->curridx);
+ unsigned spins = 0;
LgwrRqst.Write = XLogCtl->xlblocks[Insert->curridx];
for (;;)
InitXLBuffer(curridx);
return;
}
+ S_LOCK_SLEEP(&(XLogCtl->lgwr_lck), spins++);
}
-
- return;
}
static void
XLogCtlWrite *Write = &XLogCtl->Write;
char *from;
uint32 wcnt = 0;
- int i = 0;
bool usexistent;
for (; XLByteLT(LgwrResult.Write, LgwrRqst.Write);)
LgwrResult.Flush = LgwrResult.Write;
}
- for (;;)
- {
- if (!TAS(&(XLogCtl->info_lck)))
- {
- XLogCtl->LgwrResult = LgwrResult;
- if (XLByteLT(XLogCtl->LgwrRqst.Write, LgwrResult.Write))
- XLogCtl->LgwrRqst.Write = LgwrResult.Write;
- S_UNLOCK(&(XLogCtl->info_lck));
- break;
- }
- s_lock_sleep(i++);
- }
+ S_LOCK(&(XLogCtl->info_lck));
+ XLogCtl->LgwrResult = LgwrResult;
+ if (XLByteLT(XLogCtl->LgwrRqst.Write, LgwrResult.Write))
+ XLogCtl->LgwrRqst.Write = LgwrResult.Write;
+ S_UNLOCK(&(XLogCtl->info_lck));
+
Write->LgwrResult = LgwrResult;
}
uint32 _logId;
uint32 _logSeg;
char archdir[MAXPGPATH];
+ unsigned spins = 0;
if (MyLastRecPtr.xrecoff != 0)
elog(ERROR, "CreateCheckPoint: cannot be called inside transaction block");
START_CRIT_CODE;
+
+ /* Grab lock, using larger than normal sleep between tries (1 sec) */
while (TAS(&(XLogCtl->chkp_lck)))
{
- struct timeval delay = {2, 0};
-
- if (shutdown)
- elog(STOP, "Checkpoint lock is busy while data base is shutting down");
- (void) select(0, NULL, NULL, NULL, &delay);
+ S_LOCK_SLEEP_INTERVAL(&(XLogCtl->chkp_lck), spins++, 1000000);
}
memset(&checkPoint, 0, sizeof(checkPoint));
checkPoint.Shutdown = shutdown;
/* Get REDO record ptr */
- while (TAS(&(XLogCtl->insert_lck)))
- {
- struct timeval delay = {1, 0};
-
- if (shutdown)
- elog(STOP, "XLog insert lock is busy while data base is shutting down");
- (void) select(0, NULL, NULL, NULL, &delay);
- }
+ S_LOCK(&(XLogCtl->insert_lck));
freespace = ((char *) Insert->currpage) + BLCKSZ - Insert->currpos;
if (freespace < SizeOfXLogRecord)
{
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/storage/buffer/Attic/s_lock.c,v 1.27 2000/12/11 00:49:51 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/storage/buffer/Attic/s_lock.c,v 1.28 2000/12/29 21:31:20 tgl Exp $
*
*-------------------------------------------------------------------------
*/
* number of microseconds to wait. This accomplishes pseudo random back-off.
* Values are not critical but 10 milliseconds is a common platform
* granularity.
- * note: total time to cycle through all 16 entries might be about .07 sec.
+ *
+ * Total time to cycle through all 20 entries might be about .07 sec,
+ * so the given value of S_MAX_BUSY results in timeout after ~70 sec.
*/
#define S_NSPINCYCLE 20
#define S_MAX_BUSY 1000 * S_NSPINCYCLE
int s_spincycle[S_NSPINCYCLE] =
-{0, 0, 0, 0, 10000, 0, 0, 0, 10000, 0,
+{ 0, 0, 0, 0, 10000, 0, 0, 0, 10000, 0,
0, 10000, 0, 0, 10000, 0, 10000, 0, 10000, 10000
};
/*
- * s_lock_stuck(lock) - complain about a stuck spinlock
+ * s_lock_stuck() - complain about a stuck spinlock
*/
static void
s_lock_stuck(volatile slock_t *lock, const char *file, const int line)
}
+/*
+ * s_lock_sleep() - sleep a pseudo-random amount of time, check for timeout
+ *
+ * Normally 'microsec' is 0, specifying to use the next s_spincycle[] value.
+ * Some callers may pass a nonzero interval, specifying to use exactly that
+ * delay value rather than a pseudo-random delay.
+ */
void
-s_lock_sleep(unsigned spin)
+s_lock_sleep(unsigned spins, int microsec,
+ volatile slock_t *lock,
+ const char *file, const int line)
{
struct timeval delay;
+ unsigned max_spins;
+
+ if (microsec > 0)
+ {
+ delay.tv_sec = 0;
+ delay.tv_usec = microsec;
+ /* two-minute timeout in this case */
+ max_spins = 120000000 / microsec;
+ }
+ else
+ {
+ delay.tv_sec = 0;
+ delay.tv_usec = s_spincycle[spins % S_NSPINCYCLE];
+ max_spins = S_MAX_BUSY;
+ }
+
+ if (spins > max_spins)
+ s_lock_stuck(lock, file, line);
- delay.tv_sec = 0;
- delay.tv_usec = s_spincycle[spin % S_NSPINCYCLE];
(void) select(0, NULL, NULL, NULL, &delay);
}
{
unsigned spins = 0;
+ /*
+ * If you are thinking of changing this code, be careful. This same
+ * loop logic is used in other places that call TAS() directly.
+ */
while (TAS(lock))
{
- s_lock_sleep(spins);
- if (++spins > S_MAX_BUSY)
- {
- /* It's been over a minute... */
- s_lock_stuck(lock, file, line);
- }
+ s_lock_sleep(spins++, 0, lock, file, line);
}
}
/*-------------------------------------------------------------------------
*
* s_lock.h
- * This file contains the implementation (if any) for spinlocks.
+ * This file contains the in-line portion of the implementation
+ * of spinlocks.
*
* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/include/storage/s_lock.h,v 1.75 2000/12/03 14:41:42 thomas Exp $
+ * $Header: /cvsroot/pgsql/src/include/storage/s_lock.h,v 1.76 2000/12/29 21:31:20 tgl Exp $
*
*-------------------------------------------------------------------------
*/
-/*
- * DESCRIPTION
- * The public macros that must be provided are:
+/*----------
+ * DESCRIPTION
+ * The public macros that must be provided are:
+ *
+ * void S_INIT_LOCK(slock_t *lock)
+ * Initialize a spinlock (to the unlocked state).
+ *
+ * void S_LOCK(slock_t *lock)
+ * Acquire a spinlock, waiting if necessary.
+ * Time out and abort() if unable to acquire the lock in a
+ * "reasonable" amount of time --- typically ~ 1 minute.
*
- * void S_INIT_LOCK(slock_t *lock)
+ * void S_UNLOCK(slock_t *lock)
+ * Unlock a previously acquired lock.
*
- * void S_LOCK(slock_t *lock)
+ * bool S_LOCK_FREE(slock_t *lock)
+ * Tests if the lock is free. Returns TRUE if free, FALSE if locked.
+ * This does *not* change the state of the lock.
*
- * void S_UNLOCK(slock_t *lock)
+ * int TAS(slock_t *lock)
+ * Atomic test-and-set instruction. Attempt to acquire the lock,
+ * but do *not* wait. Returns 0 if successful, nonzero if unable
+ * to acquire the lock.
*
- * void S_LOCK_FREE(slock_t *lock)
- * Tests if the lock is free. Returns non-zero if free, 0 if locked.
+ * TAS() is a lower-level part of the API, but is used directly in a
+ * few places that want to do other things while waiting for a lock.
+ * The S_LOCK() macro is equivalent to
*
- * The S_LOCK() macro implements a primitive but still useful random
- * backoff to avoid hordes of busywaiting lockers chewing CPU.
+ * void
+ * S_LOCK(slock_t *lock)
+ * {
+ * unsigned spins = 0;
*
- * Effectively:
- * void
- * S_LOCK(slock_t *lock)
+ * while (TAS(lock))
* {
- * while (TAS(lock))
- * {
- * // back off the cpu for a semi-random short time
- * }
+ * S_LOCK_SLEEP(lock, spins++);
* }
+ * }
*
- * This implementation takes advantage of a tas function written
- * (in assembly language) on machines that have a native test-and-set
- * instruction. Alternative mutex implementations may also be used.
- * This function is hidden under the TAS macro to allow substitutions.
+ * where S_LOCK_SLEEP() checks for timeout and sleeps for a short
+ * interval. Callers that want to perform useful work while waiting
+ * can write out this entire loop and insert the "useful work" inside
+ * the loop.
*
- * #define TAS(lock) tas(lock)
- * int tas(slock_t *lock) // True if lock already set
+ * CAUTION to TAS() callers: on some platforms TAS() may sometimes
+ * report failure to acquire a lock even when the lock is not locked.
+ * For example, on Alpha TAS() will "fail" if interrupted. Therefore
+ * TAS() must *always* be invoked in a retry loop as depicted, even when
+ * you are certain the lock is free.
*
- * There are default implementations for all these macros at the bottom
- * of this file. Check if your platform can use these or needs to
- * override them.
+ * On most supported platforms, TAS() uses a tas() function written
+ * in assembly language to execute a hardware atomic-test-and-set
+ * instruction. Equivalent OS-supplied mutex routines could be used too.
*
- * NOTES
- * If none of this can be done, POSTGRES will default to using
- * System V semaphores (and take a large performance hit -- around 40%
- * of its time on a DS5000/240 is spent in semop(3)...).
- *
- * AIX has a test-and-set but the recommended interface is the cs(3)
- * system call. This provides an 8-instruction (plus system call
- * overhead) uninterruptible compare-and-set operation. True
- * spinlocks might be faster but using cs(3) still speeds up the
- * regression test suite by about 25%. I don't have an assembler
- * manual for POWER in any case.
+ * If no system-specific TAS() is available (ie, HAS_TEST_AND_SET is not
+ * defined), then we fall back on an emulation that uses SysV semaphores.
+ * This emulation will be MUCH MUCH MUCH slower than a proper TAS()
+ * implementation, because of the cost of a kernel call per lock or unlock.
+ * An old report is that Postgres spends around 40% of its time in semop(2)
+ * when using the SysV semaphore code.
*
+ * Note to implementors: there are default implementations for all these
+ * macros at the bottom of the file. Check if your platform can use
+ * these or needs to override them.
+ *----------
*/
#ifndef S_LOCK_H
#define S_LOCK_H
#include "storage/ipc.h"
-extern void s_lock_sleep(unsigned spin);
+/* Platform-independent out-of-line support routines */
+extern void s_lock(volatile slock_t *lock,
+ const char *file, const int line);
+extern void s_lock_sleep(unsigned spins, int microsec,
+ volatile slock_t *lock,
+ const char *file, const int line);
+
#if defined(HAS_TEST_AND_SET)
#endif /* NEED_VAX_TAS_ASM */
-
#if defined(NEED_NS32K_TAS_ASM)
#define TAS(lock) tas(lock)
-#else /* __GNUC__ */
-/***************************************************************************
- * All non gcc
- */
+#else /* !__GNUC__ */
-#if defined(__QNX__)
-/*
- * QNX 4
- *
- * Note that slock_t under QNX is sem_t instead of char
+/***************************************************************************
+ * All non-gcc inlines
*/
-#define TAS(lock) (sem_trywait((lock)) < 0)
-#define S_UNLOCK(lock) sem_post((lock))
-#define S_INIT_LOCK(lock) sem_init((lock), 1, 1)
-#define S_LOCK_FREE(lock) (lock)->value
-#endif /* __QNX__ */
-
-#if defined(NEED_I386_TAS_ASM)
-/* non gcc i386 based things */
-
-#if defined(USE_UNIVEL_CC)
+#if defined(NEED_I386_TAS_ASM) && defined(USE_UNIVEL_CC)
#define TAS(lock) tas(lock)
asm int
popl %ebx
}
-#endif /* USE_UNIVEL_CC */
-
-#endif /* NEED_I386_TAS_ASM */
+#endif /* defined(NEED_I386_TAS_ASM) && defined(USE_UNIVEL_CC) */
#endif /* defined(__GNUC__) */
/*************************************************************************
- * These are the platforms that have common code for gcc and non-gcc
+ * These are the platforms that do not use inline assembler (and hence
+ * have common code for gcc and non-gcc compilers, if both are available).
*/
* (see include/port/hpux.h).
*
* a "set" slock_t has a single word cleared. a "clear" slock_t has
- * all words set to non-zero. tas() in tas.s
+ * all words set to non-zero. tas() is in tas.s
*/
#define S_UNLOCK(lock) \
#endif /* __hpux */
+#if defined(__QNX__)
+/*
+ * QNX 4
+ *
+ * Note that slock_t under QNX is sem_t instead of char
+ */
+#define TAS(lock) (sem_trywait((lock)) < 0)
+#define S_UNLOCK(lock) sem_post((lock))
+#define S_INIT_LOCK(lock) sem_init((lock), 1, 1)
+#define S_LOCK_FREE(lock) ((lock)->value)
+#endif /* __QNX__ */
+
+
#if defined(__sgi)
/*
* SGI IRIX 5
+#else /* !HAS_TEST_AND_SET */
+
+/*
+ * Fake spinlock implementation using SysV semaphores --- slow and prone
+ * to fall foul of kernel limits on number of semaphores, so don't use this
+ * unless you must!
+ */
+
+typedef struct
+{
+ /* reference to semaphore used to implement this spinlock */
+ IpcSemaphoreId semId;
+ int sem;
+} slock_t;
+
+extern bool s_lock_free_sema(volatile slock_t *lock);
+extern void s_unlock_sema(volatile slock_t *lock);
+extern void s_init_lock_sema(volatile slock_t *lock);
+extern int tas_sema(volatile slock_t *lock);
+
+#define S_LOCK_FREE(lock) s_lock_free_sema(lock)
+#define S_UNLOCK(lock) s_unlock_sema(lock)
+#define S_INIT_LOCK(lock) s_init_lock_sema(lock)
+#define TAS(lock) tas_sema(lock)
+
+#endif /* HAS_TEST_AND_SET */
+
+
/****************************************************************************
* Default Definitions - override these above as needed.
*/
#if !defined(S_LOCK)
-extern void s_lock(volatile slock_t *lock, const char *file, const int line);
-
#define S_LOCK(lock) \
do { \
- if (TAS((volatile slock_t *) (lock))) \
- s_lock((volatile slock_t *) (lock), __FILE__, __LINE__); \
+ if (TAS(lock)) \
+ s_lock((lock), __FILE__, __LINE__); \
} while (0)
#endif /* S_LOCK */
+#if !defined(S_LOCK_SLEEP)
+#define S_LOCK_SLEEP(lock,spins) \
+ s_lock_sleep((spins), 0, (lock), __FILE__, __LINE__)
+#endif /* S_LOCK_SLEEP */
+
+#if !defined(S_LOCK_SLEEP_INTERVAL)
+#define S_LOCK_SLEEP_INTERVAL(lock,spins,microsec) \
+ s_lock_sleep((spins), (microsec), (lock), __FILE__, __LINE__)
+#endif /* S_LOCK_SLEEP_INTERVAL */
+
#if !defined(S_LOCK_FREE)
#define S_LOCK_FREE(lock) (*(lock) == 0)
#endif /* S_LOCK_FREE */
#endif /* S_INIT_LOCK */
#if !defined(TAS)
-extern int tas(volatile slock_t *lock); /* port/.../tas.s, or
+extern int tas(volatile slock_t *lock); /* in port/.../tas.s, or
* s_lock.c */
-#define TAS(lock) tas((volatile slock_t *) (lock))
+#define TAS(lock) tas(lock)
#endif /* TAS */
-#else /* !HAS_TEST_AND_SET */
-
-/*
- * Fake spinlock implementation using SysV semaphores --- slow and prone
- * to fall foul of kernel limits on number of semaphores, so don't use this
- * unless you must!
- */
-
-typedef struct
-{
- /* reference to semaphore used to implement this spinlock */
- IpcSemaphoreId semId;
- int sem;
-} slock_t;
-
-extern bool s_lock_free_sema(volatile slock_t *lock);
-extern void s_unlock_sema(volatile slock_t *lock);
-extern void s_init_lock_sema(volatile slock_t *lock);
-extern int tas_sema(volatile slock_t *lock);
-
-extern void s_lock(volatile slock_t *lock, const char *file, const int line);
-
-#define S_LOCK(lock) \
- do { \
- if (TAS((volatile slock_t *) (lock))) \
- s_lock((volatile slock_t *) (lock), __FILE__, __LINE__); \
- } while (0)
-
-#define S_LOCK_FREE(lock) s_lock_free_sema(lock)
-#define S_UNLOCK(lock) s_unlock_sema(lock)
-#define S_INIT_LOCK(lock) s_init_lock_sema(lock)
-#define TAS(lock) tas_sema(lock)
-
-#endif /* HAS_TEST_AND_SET */
-
#endif /* S_LOCK_H */
projects / postgresql / commitdiff