diff options
Diffstat (limited to 'src/backend/storage/lmgr/spin.c')
| -rw-r--r-- | src/backend/storage/lmgr/spin.c | 143 |
1 files changed, 24 insertions, 119 deletions
diff --git a/src/backend/storage/lmgr/spin.c b/src/backend/storage/lmgr/spin.c index f5bb8e34889..c384c4b1586 100644 --- a/src/backend/storage/lmgr/spin.c +++ b/src/backend/storage/lmgr/spin.c @@ -6,7 +6,8 @@ * * For machines that have test-and-set (TAS) instructions, s_lock.h/.c * define the spinlock implementation. This file contains only a stub - * implementation for spinlocks using SysV semaphores. The semaphore method + * implementation for spinlocks using PGSemaphores. Unless semaphores + * are implemented in a way that doesn't involve a kernel call, this * is too slow to be very useful :-( * * @@ -15,143 +16,49 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/storage/lmgr/spin.c,v 1.7 2001/11/05 17:46:28 momjian Exp $ + * $Header: /cvsroot/pgsql/src/backend/storage/lmgr/spin.c,v 1.8 2002/05/05 00:03:28 tgl Exp $ * *------------------------------------------------------------------------- */ #include "postgres.h" -#include <errno.h> - -#include "storage/ipc.h" -/* In Ultrix, sem.h and shm.h must be included AFTER ipc.h */ -#ifdef HAVE_SYS_SEM_H -#include <sys/sem.h> -#endif - -#if defined(__darwin__) -#include "port/darwin/sem.h" -#endif - #include "storage/lwlock.h" -#include "storage/proc.h" +#include "storage/pg_sema.h" #include "storage/spin.h" #ifdef HAS_TEST_AND_SET /* - * CreateSpinlocks --- create and initialize spinlocks during startup + * Report number of semaphores needed to support spinlocks. */ -void -CreateSpinlocks(void) +int +SpinlockSemas(void) { - /* no-op when we have TAS spinlocks */ + return 0; } #else /* !HAS_TEST_AND_SET */ /* - * No TAS, so spinlocks are implemented using SysV semaphores. - * - * Typedef slock_t stores the semId and sem number of the sema to use. - * The semas needed are created by CreateSpinlocks and doled out by - * s_init_lock_sema. - * - * Since many systems have a rather small SEMMSL limit on semas per set, - * we allocate the semaphores required in sets of SPINLOCKS_PER_SET semas. - * This value is deliberately made equal to PROC_NSEMS_PER_SET so that all - * sema sets allocated by Postgres will be the same size; that eases the - * semaphore-recycling logic in IpcSemaphoreCreate(). - * - * Note that the SpinLockIds array is not in shared memory; it is filled - * by the postmaster and then inherited through fork() by backends. This - * is OK because its contents do not change after shmem initialization. + * No TAS, so spinlocks are implemented as PGSemaphores. */ -#define SPINLOCKS_PER_SET PROC_NSEMS_PER_SET - -static IpcSemaphoreId *SpinLockIds = NULL; - -static int numSpinSets = 0; /* number of sema sets used */ -static int numSpinLocks = 0; /* total number of semas allocated */ -static int nextSpinLock = 0; /* next free spinlock index */ - -static void SpinFreeAllSemaphores(void); - /* - * CreateSpinlocks --- create and initialize spinlocks during startup + * Report number of semaphores needed to support spinlocks. */ -void -CreateSpinlocks(void) +int +SpinlockSemas(void) { - int i; - - if (SpinLockIds == NULL) - { - /* - * Compute number of spinlocks needed. It would be cleaner to - * distribute this logic into the affected modules, similar to the - * way shmem space estimation is handled. - * - * For now, though, we just need a few spinlocks (10 should be - * plenty) plus one for each LWLock. - */ - numSpinLocks = NumLWLocks() + 10; - - /* might as well round up to a multiple of SPINLOCKS_PER_SET */ - numSpinSets = (numSpinLocks - 1) / SPINLOCKS_PER_SET + 1; - numSpinLocks = numSpinSets * SPINLOCKS_PER_SET; - - SpinLockIds = (IpcSemaphoreId *) - malloc(numSpinSets * sizeof(IpcSemaphoreId)); - Assert(SpinLockIds != NULL); - } - - for (i = 0; i < numSpinSets; i++) - SpinLockIds[i] = -1; - /* - * Arrange to delete semas on exit --- set this up now so that we will - * clean up if allocation fails. We use our own freeproc, rather than - * IpcSemaphoreCreate's removeOnExit option, because we don't want to - * fill up the on_shmem_exit list with a separate entry for each - * semaphore set. + * It would be cleaner to distribute this logic into the affected modules, + * similar to the way shmem space estimation is handled. + * + * For now, though, we just need a few spinlocks (10 should be + * plenty) plus one for each LWLock. */ - on_shmem_exit(SpinFreeAllSemaphores, 0); - - /* Create sema sets and set all semas to count 1 */ - for (i = 0; i < numSpinSets; i++) - { - SpinLockIds[i] = IpcSemaphoreCreate(SPINLOCKS_PER_SET, - IPCProtection, - 1, - false); - } - - /* Init counter for allocating dynamic spinlocks */ - nextSpinLock = 0; -} - -/* - * SpinFreeAllSemaphores - - * called at shmem_exit time, ie when exiting the postmaster or - * destroying shared state for a failed set of backends. - * Free up all the semaphores allocated for spinlocks. - */ -static void -SpinFreeAllSemaphores(void) -{ - int i; - - for (i = 0; i < numSpinSets; i++) - { - if (SpinLockIds[i] >= 0) - IpcSemaphoreKill(SpinLockIds[i]); - } - free(SpinLockIds); - SpinLockIds = NULL; + return NumLWLocks() + 10; } /* @@ -161,30 +68,28 @@ SpinFreeAllSemaphores(void) void s_init_lock_sema(volatile slock_t *lock) { - if (nextSpinLock >= numSpinLocks) - elog(FATAL, "s_init_lock_sema: not enough semaphores"); - lock->semId = SpinLockIds[nextSpinLock / SPINLOCKS_PER_SET]; - lock->sem = nextSpinLock % SPINLOCKS_PER_SET; - nextSpinLock++; + PGSemaphoreCreate((PGSemaphore) lock); } void s_unlock_sema(volatile slock_t *lock) { - IpcSemaphoreUnlock(lock->semId, lock->sem); + PGSemaphoreUnlock((PGSemaphore) lock); } bool s_lock_free_sema(volatile slock_t *lock) { - return IpcSemaphoreGetValue(lock->semId, lock->sem) > 0; + /* We don't currently use S_LOCK_FREE anyway */ + elog(ERROR, "spin.c does not support S_LOCK_FREE()"); + return false; } int tas_sema(volatile slock_t *lock) { /* Note that TAS macros return 0 if *success* */ - return !IpcSemaphoreTryLock(lock->semId, lock->sem); + return !PGSemaphoreTryLock((PGSemaphore) lock); } #endif /* !HAS_TEST_AND_SET */ |