From: Nathan Bossart Date: Thu, 9 Jul 2026 15:38:08 -0500 Subject: [PATCH v1 8/8] convert FastPathStrongRelationLocks to atomics --- 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--