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help / color / mirror / Atom feedFrom: Nathan Bossart <[email protected]>
Subject: [PATCH v1 8/8] convert FastPathStrongRelationLocks to atomics
Date: Thu, 9 Jul 2026 15:38:08 -0500
---
src/backend/storage/lmgr/lock.c | 57 ++++++++++-----------------------
1 file changed, 17 insertions(+), 40 deletions(-)
diff --git a/src/backend/storage/lmgr/lock.c b/src/backend/storage/lmgr/lock.c
index 5ee80c7632e..035932197a4 100644
--- a/src/backend/storage/lmgr/lock.c
+++ b/src/backend/storage/lmgr/lock.c
@@ -40,11 +40,11 @@
#include "miscadmin.h"
#include "pg_trace.h"
#include "pgstat.h"
+#include "port/atomics.h"
#include "storage/lmgr.h"
#include "storage/proc.h"
#include "storage/procarray.h"
#include "storage/shmem.h"
-#include "storage/spin.h"
#include "storage/standby.h"
#include "storage/subsystems.h"
#include "utils/memutils.h"
@@ -306,13 +306,7 @@ static PROCLOCK *FastPathGetRelationLockEntry(LOCALLOCK *locallock);
#define FastPathStrongLockHashPartition(hashcode) \
((hashcode) % FAST_PATH_STRONG_LOCK_HASH_PARTITIONS)
-typedef struct
-{
- slock_t mutex;
- uint32 count[FAST_PATH_STRONG_LOCK_HASH_PARTITIONS];
-} FastPathStrongRelationLockData;
-
-static FastPathStrongRelationLockData *FastPathStrongRelationLocks;
+static pg_atomic_uint32 *FastPathStrongRelationLocks;
static void LockManagerShmemRequest(void *arg);
static void LockManagerShmemInit(void *arg);
@@ -484,7 +478,8 @@ LockManagerShmemRequest(void *arg)
);
ShmemRequestStruct(.name = "Fast Path Strong Relation Lock Data",
- .size = sizeof(FastPathStrongRelationLockData),
+ .size = mul_size(sizeof(pg_atomic_uint32),
+ FAST_PATH_STRONG_LOCK_HASH_PARTITIONS),
.ptr = (void **) (void *) &FastPathStrongRelationLocks,
);
}
@@ -492,7 +487,8 @@ LockManagerShmemRequest(void *arg)
static void
LockManagerShmemInit(void *arg)
{
- SpinLockInit(&FastPathStrongRelationLocks->mutex);
+ for (int i = 0; i < FAST_PATH_STRONG_LOCK_HASH_PARTITIONS; i++)
+ pg_atomic_init_u32(&FastPathStrongRelationLocks[i], 0);
}
/*
@@ -992,11 +988,11 @@ LockAcquireExtended(const LOCKTAG *locktag,
/*
* LWLockAcquire acts as a memory sequencing point, so it's safe
* to assume that any strong locker whose increment to
- * FastPathStrongRelationLocks->counts becomes visible after we
- * test it has yet to begin to transfer fast-path locks.
+ * FastPathStrongRelationLocks becomes visible after we test it
+ * has yet to begin to transfer fast-path locks.
*/
LWLockAcquire(&MyProc->fpInfoLock, LW_EXCLUSIVE);
- if (FastPathStrongRelationLocks->count[fasthashcode] != 0)
+ if (pg_atomic_read_u32(&FastPathStrongRelationLocks[fasthashcode]) != 0)
acquired = false;
else
acquired = FastPathGrantRelationLock(locktag->locktag_field2,
@@ -1501,11 +1497,9 @@ RemoveLocalLock(LOCALLOCK *locallock)
fasthashcode = FastPathStrongLockHashPartition(locallock->hashcode);
- SpinLockAcquire(&FastPathStrongRelationLocks->mutex);
- Assert(FastPathStrongRelationLocks->count[fasthashcode] > 0);
- FastPathStrongRelationLocks->count[fasthashcode]--;
+ Assert(pg_atomic_read_u32(&FastPathStrongRelationLocks[fasthashcode]) > 0);
+ pg_atomic_fetch_sub_u32(&FastPathStrongRelationLocks[fasthashcode], 1);
locallock->holdsStrongLockCount = false;
- SpinLockRelease(&FastPathStrongRelationLocks->mutex);
}
if (!hash_search(LockMethodLocalHash,
@@ -1834,20 +1828,9 @@ BeginStrongLockAcquire(LOCALLOCK *locallock, uint32 fasthashcode)
Assert(StrongLockInProgress == NULL);
Assert(locallock->holdsStrongLockCount == false);
- /*
- * Adding to a memory location is not atomic, so we take a spinlock to
- * ensure we don't collide with someone else trying to bump the count at
- * the same time.
- *
- * XXX: It might be worth considering using an atomic fetch-and-add
- * instruction here, on architectures where that is supported.
- */
-
- SpinLockAcquire(&FastPathStrongRelationLocks->mutex);
- FastPathStrongRelationLocks->count[fasthashcode]++;
+ pg_atomic_fetch_add_u32(&FastPathStrongRelationLocks[fasthashcode], 1);
locallock->holdsStrongLockCount = true;
StrongLockInProgress = locallock;
- SpinLockRelease(&FastPathStrongRelationLocks->mutex);
}
/*
@@ -1875,12 +1858,10 @@ AbortStrongLockAcquire(void)
fasthashcode = FastPathStrongLockHashPartition(locallock->hashcode);
Assert(locallock->holdsStrongLockCount == true);
- SpinLockAcquire(&FastPathStrongRelationLocks->mutex);
- Assert(FastPathStrongRelationLocks->count[fasthashcode] > 0);
- FastPathStrongRelationLocks->count[fasthashcode]--;
+ Assert(pg_atomic_read_u32(&FastPathStrongRelationLocks[fasthashcode]) > 0);
+ pg_atomic_fetch_sub_u32(&FastPathStrongRelationLocks[fasthashcode], 1);
locallock->holdsStrongLockCount = false;
StrongLockInProgress = NULL;
- SpinLockRelease(&FastPathStrongRelationLocks->mutex);
}
/*
@@ -3365,10 +3346,8 @@ LockRefindAndRelease(LockMethod lockMethodTable, PGPROC *proc,
{
uint32 fasthashcode = FastPathStrongLockHashPartition(hashcode);
- SpinLockAcquire(&FastPathStrongRelationLocks->mutex);
- Assert(FastPathStrongRelationLocks->count[fasthashcode] > 0);
- FastPathStrongRelationLocks->count[fasthashcode]--;
- SpinLockRelease(&FastPathStrongRelationLocks->mutex);
+ Assert(pg_atomic_read_u32(&FastPathStrongRelationLocks[fasthashcode]) > 0);
+ pg_atomic_fetch_sub_u32(&FastPathStrongRelationLocks[fasthashcode], 1);
}
}
@@ -4504,9 +4483,7 @@ lock_twophase_recover(FullTransactionId fxid, uint16 info,
{
uint32 fasthashcode = FastPathStrongLockHashPartition(hashcode);
- SpinLockAcquire(&FastPathStrongRelationLocks->mutex);
- FastPathStrongRelationLocks->count[fasthashcode]++;
- SpinLockRelease(&FastPathStrongRelationLocks->mutex);
+ pg_atomic_fetch_add_u32(&FastPathStrongRelationLocks[fasthashcode], 1);
}
LWLockRelease(partitionLock);
--
2.50.1 (Apple Git-155)
--Ot5x3ffkWEuxilWO--
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