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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.

Author: Thomas Munro
Discussion: https://postgr.es/m/CAEepm=204T37SxcHo4=xw5btho9jQ-=ZYYrVdcKyz82XYzMoqg@mail.gmail.com
This commit is contained in:
Andres Freund 2018-03-01 16:21:52 -08:00
parent 8ecdc2ffe3
commit 07c6e5163e
1 changed files with 27 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

60
src/backend/storage/ipc/shm_mq.c
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@ -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;