From e584628bb846be11a137b5216e955284dfd646a5 Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Thu, 8 Feb 2018 18:50:32 +1300 Subject: [PATCH] Remove volatile qualifiers from shm_mq.c. Since commit 0709b7ee, spinlock primitives include a compiler barrier so it is no longer necessary to access either spinlocks or the memory they protect through pointer-to-volatile. Like earlier commits e93b6298, d53e3d5f, 430008b5, 8f6bb851, df4077cd. Thomas Munro --- src/backend/storage/ipc/shm_mq.c | 60 ++++++++++++++++++---------------------- 1 file changed, 27 insertions(+), 33 deletions(-) diff --git a/src/backend/storage/ipc/shm_mq.c b/src/backend/storage/ipc/shm_mq.c index 1131e27e2e7..5a2a16c995d 100644 --- a/src/backend/storage/ipc/shm_mq.c +++ b/src/backend/storage/ipc/shm_mq.c @@ -146,15 +146,15 @@ static shm_mq_result shm_mq_send_bytes(shm_mq_handle *mq, Size nbytes, const void *data, bool nowait, Size *bytes_written); static shm_mq_result shm_mq_receive_bytes(shm_mq *mq, Size bytes_needed, bool nowait, Size *nbytesp, void **datap); -static bool shm_mq_counterparty_gone(volatile shm_mq *mq, +static bool shm_mq_counterparty_gone(shm_mq *mq, BackgroundWorkerHandle *handle); -static bool shm_mq_wait_internal(volatile shm_mq *mq, PGPROC *volatile *ptr, +static bool shm_mq_wait_internal(shm_mq *mq, PGPROC **ptr, BackgroundWorkerHandle *handle); -static uint64 shm_mq_get_bytes_read(volatile shm_mq *mq, bool *detached); -static void shm_mq_inc_bytes_read(volatile shm_mq *mq, Size n); -static uint64 shm_mq_get_bytes_written(volatile shm_mq *mq, bool *detached); -static void shm_mq_inc_bytes_written(volatile shm_mq *mq, Size n); -static shm_mq_result shm_mq_notify_receiver(volatile shm_mq *mq); +static uint64 shm_mq_get_bytes_read(shm_mq *mq, bool *detached); +static void shm_mq_inc_bytes_read(shm_mq *mq, Size n); +static uint64 shm_mq_get_bytes_written(shm_mq *mq, bool *detached); +static void shm_mq_inc_bytes_written(shm_mq *mq, Size n); +static shm_mq_result shm_mq_notify_receiver(shm_mq *mq); static void shm_mq_detach_callback(dsm_segment *seg, Datum arg); /* Minimum queue size is enough for header and at least one chunk of data. */ @@ -198,13 +198,12 @@ shm_mq_create(void *address, Size size) void shm_mq_set_receiver(shm_mq *mq, PGPROC *proc) { - volatile shm_mq *vmq = mq; PGPROC *sender; SpinLockAcquire(&mq->mq_mutex); - Assert(vmq->mq_receiver == NULL); - vmq->mq_receiver = proc; - sender = vmq->mq_sender; + Assert(mq->mq_receiver == NULL); + mq->mq_receiver = proc; + sender = mq->mq_sender; SpinLockRelease(&mq->mq_mutex); if (sender != NULL) @@ -217,13 +216,12 @@ shm_mq_set_receiver(shm_mq *mq, PGPROC *proc) void shm_mq_set_sender(shm_mq *mq, PGPROC *proc) { - volatile shm_mq *vmq = mq; PGPROC *receiver; SpinLockAcquire(&mq->mq_mutex); - Assert(vmq->mq_sender == NULL); - vmq->mq_sender = proc; - receiver = vmq->mq_receiver; + Assert(mq->mq_sender == NULL); + mq->mq_sender = proc; + receiver = mq->mq_receiver; SpinLockRelease(&mq->mq_mutex); if (receiver != NULL) @@ -236,11 +234,10 @@ shm_mq_set_sender(shm_mq *mq, PGPROC *proc) PGPROC * shm_mq_get_receiver(shm_mq *mq) { - volatile shm_mq *vmq = mq; PGPROC *receiver; SpinLockAcquire(&mq->mq_mutex); - receiver = vmq->mq_receiver; + receiver = mq->mq_receiver; SpinLockRelease(&mq->mq_mutex); return receiver; @@ -252,11 +249,10 @@ shm_mq_get_receiver(shm_mq *mq) PGPROC * shm_mq_get_sender(shm_mq *mq) { - volatile shm_mq *vmq = mq; PGPROC *sender; SpinLockAcquire(&mq->mq_mutex); - sender = vmq->mq_sender; + sender = mq->mq_sender; SpinLockRelease(&mq->mq_mutex); return sender; @@ -806,18 +802,17 @@ shm_mq_detach(shm_mq_handle *mqh) static void shm_mq_detach_internal(shm_mq *mq) { - volatile shm_mq *vmq = mq; PGPROC *victim; SpinLockAcquire(&mq->mq_mutex); - if (vmq->mq_sender == MyProc) - victim = vmq->mq_receiver; + if (mq->mq_sender == MyProc) + victim = mq->mq_receiver; else { - Assert(vmq->mq_receiver == MyProc); - victim = vmq->mq_sender; + Assert(mq->mq_receiver == MyProc); + victim = mq->mq_sender; } - vmq->mq_detached = true; + mq->mq_detached = true; SpinLockRelease(&mq->mq_mutex); if (victim != NULL) @@ -1035,7 +1030,7 @@ shm_mq_receive_bytes(shm_mq *mq, Size bytes_needed, bool nowait, * Test whether a counterparty who may not even be alive yet is definitely gone. */ static bool -shm_mq_counterparty_gone(volatile shm_mq *mq, BackgroundWorkerHandle *handle) +shm_mq_counterparty_gone(shm_mq *mq, BackgroundWorkerHandle *handle) { bool detached; pid_t pid; @@ -1082,8 +1077,7 @@ shm_mq_counterparty_gone(volatile shm_mq *mq, BackgroundWorkerHandle *handle) * non-NULL when our counterpart attaches to the queue. */ static bool -shm_mq_wait_internal(volatile shm_mq *mq, PGPROC *volatile *ptr, - BackgroundWorkerHandle *handle) +shm_mq_wait_internal(shm_mq *mq, PGPROC **ptr, BackgroundWorkerHandle *handle) { bool result = false; @@ -1137,7 +1131,7 @@ shm_mq_wait_internal(volatile shm_mq *mq, PGPROC *volatile *ptr, * the count of bytes read, but the sender must. */ static uint64 -shm_mq_get_bytes_read(volatile shm_mq *mq, bool *detached) +shm_mq_get_bytes_read(shm_mq *mq, bool *detached) { uint64 v; @@ -1153,7 +1147,7 @@ shm_mq_get_bytes_read(volatile shm_mq *mq, bool *detached) * Increment the number of bytes read. */ static void -shm_mq_inc_bytes_read(volatile shm_mq *mq, Size n) +shm_mq_inc_bytes_read(shm_mq *mq, Size n) { PGPROC *sender; @@ -1172,7 +1166,7 @@ shm_mq_inc_bytes_read(volatile shm_mq *mq, Size n) * the count of bytes written, but the receiver must. */ static uint64 -shm_mq_get_bytes_written(volatile shm_mq *mq, bool *detached) +shm_mq_get_bytes_written(shm_mq *mq, bool *detached) { uint64 v; @@ -1188,7 +1182,7 @@ shm_mq_get_bytes_written(volatile shm_mq *mq, bool *detached) * Increment the number of bytes written. */ static void -shm_mq_inc_bytes_written(volatile shm_mq *mq, Size n) +shm_mq_inc_bytes_written(shm_mq *mq, Size n) { SpinLockAcquire(&mq->mq_mutex); mq->mq_bytes_written += n; @@ -1199,7 +1193,7 @@ shm_mq_inc_bytes_written(volatile shm_mq *mq, Size n) * Set receiver's latch, unless queue is detached. */ static shm_mq_result -shm_mq_notify_receiver(volatile shm_mq *mq) +shm_mq_notify_receiver(shm_mq *mq) { PGPROC *receiver; bool detached; -- 2.15.1