3 files changed, 50 insertions, 22 deletions

diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c
index 1c8783f2c08..3c04fc31bae 100644
--- a/src/backend/storage/ipc/ipci.c
+++ b/src/backend/storage/ipc/ipci.c
@@ -105,6 +105,7 @@ CreateSharedMemoryAndSemaphores(bool makePrivate, int port)
 		 * need to be so careful during the actual allocation phase.
 		 */
 		size = 100000;
+		size = add_size(size, SpinlockSemaSize());
 		size = add_size(size, hash_estimate_size(SHMEM_INDEX_SIZE,
 												 sizeof(ShmemIndexEnt)));
 		size = add_size(size, BufferShmemSize());
diff --git a/src/backend/storage/ipc/shmem.c b/src/backend/storage/ipc/shmem.c
index e93b988ad74..70b02ca8384 100644
--- a/src/backend/storage/ipc/shmem.c
+++ b/src/backend/storage/ipc/shmem.c
@@ -116,9 +116,24 @@ InitShmemAllocation(void)
 	Assert(shmhdr != NULL);
 
 	/*
-	 * Initialize the spinlock used by ShmemAlloc.	We have to do the space
-	 * allocation the hard way, since obviously ShmemAlloc can't be called
-	 * yet.
+	 * If spinlocks are disabled, initialize emulation layer.  We have to do
+	 * the space allocation the hard way, since obviously ShmemAlloc can't be
+	 * called yet.
+	 */
+#ifndef HAVE_SPINLOCKS
+	{
+		PGSemaphore spinsemas;
+
+		spinsemas = (PGSemaphore) (((char *) shmhdr) + shmhdr->freeoffset);
+		shmhdr->freeoffset += MAXALIGN(SpinlockSemaSize());
+		SpinlockSemaInit(spinsemas);
+		Assert(shmhdr->freeoffset <= shmhdr->totalsize);
+	}
+#endif
+
+	/*
+	 * Initialize the spinlock used by ShmemAlloc; we have to do this the hard
+	 * way, too, for the same reasons as above.
 	 */
 	ShmemLock = (slock_t *) (((char *) shmhdr) + shmhdr->freeoffset);
 	shmhdr->freeoffset += MAXALIGN(sizeof(slock_t));
diff --git a/src/backend/storage/lmgr/spin.c b/src/backend/storage/lmgr/spin.c
index 08782178de9..3d116bc7a2e 100644
--- a/src/backend/storage/lmgr/spin.c
+++ b/src/backend/storage/lmgr/spin.c
@@ -29,6 +29,18 @@
 #include "storage/spin.h"
 
 
+PGSemaphore SpinlockSemaArray;
+
+/*
+ * Report the amount of shared memory needed to store semaphores for spinlock
+ * support.
+ */
+Size
+SpinlockSemaSize(void)
+{
+	return SpinlockSemas() * sizeof(PGSemaphoreData);
+}
+
 #ifdef HAVE_SPINLOCKS
 
 /*
@@ -52,22 +64,20 @@ SpinlockSemas(void)
 int
 SpinlockSemas(void)
 {
-	int			nsemas;
-
-	/*
-	 * It would be cleaner to distribute this logic into the affected modules,
-	 * similar to the way shmem space estimation is handled.
-	 *
-	 * For now, though, there are few enough users of spinlocks that we just
-	 * keep the knowledge here.
-	 */
-	nsemas = NumLWLocks();		/* one for each lwlock */
-	nsemas += NBuffers;			/* one for each buffer header */
-	nsemas += max_wal_senders;	/* one for each wal sender process */
-	nsemas += num_xloginsert_slots; /* one for each WAL insertion slot */
-	nsemas += 30;				/* plus a bunch for other small-scale use */
-
-	return nsemas;
+	return NUM_SPINLOCK_SEMAPHORES;
+}
+
+/*
+ * Initialize semaphores.
+ */
+extern void
+SpinlockSemaInit(PGSemaphore spinsemas)
+{
+	int	i;
+
+	for (i = 0; i < NUM_SPINLOCK_SEMAPHORES; ++i)
+		PGSemaphoreCreate(&spinsemas[i]);
+	SpinlockSemaArray = spinsemas;
 }
 
 /*
@@ -77,13 +87,15 @@ SpinlockSemas(void)
 void
 s_init_lock_sema(volatile slock_t *lock)
 {
-	PGSemaphoreCreate((PGSemaphore) lock);
+	static int counter = 0;
+
+	*lock = (++counter) % NUM_SPINLOCK_SEMAPHORES;
 }
 
 void
 s_unlock_sema(volatile slock_t *lock)
 {
-	PGSemaphoreUnlock((PGSemaphore) lock);
+	PGSemaphoreUnlock(&SpinlockSemaArray[*lock]);
 }
 
 bool
@@ -98,7 +110,7 @@ int
 tas_sema(volatile slock_t *lock)
 {
 	/* Note that TAS macros return 0 if *success* */
-	return !PGSemaphoreTryLock((PGSemaphore) lock);
+	return !PGSemaphoreTryLock(&SpinlockSemaArray[*lock]);
 }
 
 #endif   /* !HAVE_SPINLOCKS */