#include "postmaster/bgworker.h"
#include "storage/dsm.h"
#include "storage/proc.h"

Include dependency graph for shm_mq.h:

This graph shows which files directly or indirectly include this file:

Data Structures
struct	shm_mq_iovec

Typedefs
typedef struct shm_mq	shm_mq

typedef struct shm_mq_handle	shm_mq_handle

Enumerations
enum	shm_mq_result { SHM_MQ_SUCCESS, SHM_MQ_WOULD_BLOCK, SHM_MQ_DETACHED }

Functions
shm_mq *	shm_mq_create (void *address, Size size)

void	shm_mq_set_receiver (shm_mq mq, PGPROC )

void	shm_mq_set_sender (shm_mq mq, PGPROC )

PGPROC *	shm_mq_get_receiver (shm_mq *)

PGPROC *	shm_mq_get_sender (shm_mq *)

shm_mq_handle *	shm_mq_attach (shm_mq mq, dsm_segment seg, BackgroundWorkerHandle *handle)

void	shm_mq_set_handle (shm_mq_handle , BackgroundWorkerHandle )

void	shm_mq_detach (shm_mq *)

shm_mq *	shm_mq_get_queue (shm_mq_handle *mqh)

shm_mq_result	shm_mq_send (shm_mq_handle mqh, Size nbytes, const void data, bool nowait)

shm_mq_result	shm_mq_sendv (shm_mq_handle mqh, shm_mq_iovec iov, int iovcnt, bool nowait)

shm_mq_result	shm_mq_receive (shm_mq_handle mqh, Size nbytesp, void **datap, bool nowait)

shm_mq_result	shm_mq_wait_for_attach (shm_mq_handle *mqh)

Variables
PGDLLIMPORT const Size	shm_mq_minimum_size

Typedef Documentation

typedef struct shm_mq shm_mq

Definition at line 22 of file shm_mq.h.

typedef struct shm_mq_handle shm_mq_handle

Definition at line 26 of file shm_mq.h.

Enumeration Type Documentation

enum shm_mq_result

Enumerator
SHM_MQ_SUCCESS
SHM_MQ_WOULD_BLOCK
SHM_MQ_DETACHED

Definition at line 36 of file shm_mq.h.

 {
     SHM_MQ_SUCCESS,             /* Sent or received a message. */
     SHM_MQ_WOULD_BLOCK,         /* Not completed; retry later. */
     SHM_MQ_DETACHED             /* Other process has detached queue. */
 } shm_mq_result;

Function Documentation

shm_mq_handle* shm_mq_attach	(	shm_mq *	mq,
		dsm_segment *	seg,
		BackgroundWorkerHandle *	handle
	)

Definition at line 284 of file shm_mq.c.

References Assert, CurrentMemoryContext, shm_mq::mq_receiver, shm_mq::mq_sender, shm_mq_handle::mqh_buffer, shm_mq_handle::mqh_buflen, shm_mq_handle::mqh_consume_pending, shm_mq_handle::mqh_context, shm_mq_handle::mqh_counterparty_attached, shm_mq_handle::mqh_handle, shm_mq_handle::mqh_length_word_complete, shm_mq_handle::mqh_partial_bytes, shm_mq_handle::mqh_queue, shm_mq_handle::mqh_segment, MyProc, NULL, on_dsm_detach(), palloc(), PointerGetDatum, and shm_mq_detach_callback().

Referenced by attach_to_queues(), ExecParallelGetReceiver(), ExecParallelSetupTupleQueues(), InitializeParallelDSM(), ParallelWorkerMain(), ReinitializeParallelDSM(), and test_shm_mq_setup().

 {
     shm_mq_handle *mqh = palloc(sizeof(shm_mq_handle));
 
     Assert(mq->mq_receiver == MyProc || mq->mq_sender == MyProc);
     mqh->mqh_queue = mq;
     mqh->mqh_segment = seg;
     mqh->mqh_buffer = NULL;
     mqh->mqh_handle = handle;
     mqh->mqh_buflen = 0;
     mqh->mqh_consume_pending = 0;
     mqh->mqh_context = CurrentMemoryContext;
     mqh->mqh_partial_bytes = 0;
     mqh->mqh_length_word_complete = false;
     mqh->mqh_counterparty_attached = false;
 
     if (seg != NULL)
         on_dsm_detach(seg, shm_mq_detach_callback, PointerGetDatum(mq));
 
     return mqh;
 }

shm_mq* shm_mq_create	(	void *	address,
		Size	size
	)

Definition at line 167 of file shm_mq.c.

References Assert, MAXALIGN, MAXALIGN_DOWN, shm_mq::mq_bytes_read, shm_mq::mq_bytes_written, shm_mq::mq_detached, shm_mq::mq_mutex, shm_mq::mq_receiver, shm_mq::mq_ring_offset, shm_mq::mq_ring_size, shm_mq::mq_sender, NULL, offsetof, and SpinLockInit.

Referenced by ExecParallelSetupTupleQueues(), InitializeParallelDSM(), ReinitializeParallelDSM(), and setup_dynamic_shared_memory().

 {
     shm_mq     *mq = address;
     Size        data_offset = MAXALIGN(offsetof(shm_mq, mq_ring));
 
     /* If the size isn't MAXALIGN'd, just discard the odd bytes. */
     size = MAXALIGN_DOWN(size);
 
     /* Queue size must be large enough to hold some data. */
     Assert(size > data_offset);
 
     /* Initialize queue header. */
     SpinLockInit(&mq->mq_mutex);
     mq->mq_receiver = NULL;
     mq->mq_sender = NULL;
     mq->mq_bytes_read = 0;
     mq->mq_bytes_written = 0;
     mq->mq_ring_size = size - data_offset;
     mq->mq_detached = false;
     mq->mq_ring_offset = data_offset - offsetof(shm_mq, mq_ring);
 
     return mq;
 }

void shm_mq_detach ( shm_mq * )

Definition at line 778 of file shm_mq.c.

References Assert, shm_mq::mq_detached, shm_mq::mq_mutex, shm_mq::mq_receiver, shm_mq::mq_sender, MyProc, NULL, PGPROC::procLatch, SetLatch(), SpinLockAcquire, and SpinLockRelease.

Referenced by DestroyTupleQueueReader(), mq_putmessage(), shm_mq_detach_callback(), and tqueueShutdownReceiver().

 {
     volatile shm_mq *vmq = mq;
     PGPROC     *victim;
 
     SpinLockAcquire(&mq->mq_mutex);
     if (vmq->mq_sender == MyProc)
         victim = vmq->mq_receiver;
     else
     {
         Assert(vmq->mq_receiver == MyProc);
         victim = vmq->mq_sender;
     }
     vmq->mq_detached = true;
     SpinLockRelease(&mq->mq_mutex);
 
     if (victim != NULL)
         SetLatch(&victim->procLatch);
 }

shm_mq* shm_mq_get_queue ( shm_mq_handle * mqh )

Definition at line 802 of file shm_mq.c.

References shm_mq_handle::mqh_queue.

Referenced by DestroyTupleQueueReader(), pq_redirect_to_shm_mq(), and tqueueShutdownReceiver().

 {
     return mqh->mqh_queue;
 }

PGPROC* shm_mq_get_receiver ( shm_mq * )

Definition at line 234 of file shm_mq.c.

References shm_mq::mq_mutex, shm_mq::mq_receiver, SpinLockAcquire, and SpinLockRelease.

Referenced by shm_mq_send_bytes(), and shm_mq_wait_for_attach().

 {
     volatile shm_mq *vmq = mq;
     PGPROC     *receiver;
 
     SpinLockAcquire(&mq->mq_mutex);
     receiver = vmq->mq_receiver;
     SpinLockRelease(&mq->mq_mutex);
 
     return receiver;
 }

PGPROC* shm_mq_get_sender ( shm_mq * )

Definition at line 250 of file shm_mq.c.

References shm_mq::mq_mutex, shm_mq::mq_sender, SpinLockAcquire, and SpinLockRelease.

Referenced by shm_mq_receive(), and shm_mq_wait_for_attach().

 {
     volatile shm_mq *vmq = mq;
     PGPROC     *sender;
 
     SpinLockAcquire(&mq->mq_mutex);
     sender = vmq->mq_sender;
     SpinLockRelease(&mq->mq_mutex);
 
     return sender;
 }

shm_mq_result shm_mq_receive	(	shm_mq_handle *	mqh,
		Size *	nbytesp,
		void **	datap,
		bool	nowait
	)

Definition at line 518 of file shm_mq.c.

Referenced by copy_messages(), HandleParallelMessages(), test_shm_mq(), test_shm_mq_pipelined(), and TupleQueueReaderNext().

 {
     shm_mq     *mq = mqh->mqh_queue;
     shm_mq_result res;
     Size        rb = 0;
     Size        nbytes;
     void       *rawdata;
 
     Assert(mq->mq_receiver == MyProc);
 
     /* We can't receive data until the sender has attached. */
     if (!mqh->mqh_counterparty_attached)
     {
         if (nowait)
         {
             int         counterparty_gone;
 
             /*
              * We shouldn't return at this point at all unless the sender
              * hasn't attached yet.  However, the correct return value depends
              * on whether the sender is still attached.  If we first test
              * whether the sender has ever attached and then test whether the
              * sender has detached, there's a race condition: a sender that
              * attaches and detaches very quickly might fool us into thinking
              * the sender never attached at all.  So, test whether our
              * counterparty is definitively gone first, and only afterwards
              * check whether the sender ever attached in the first place.
              */
             counterparty_gone = shm_mq_counterparty_gone(mq, mqh->mqh_handle);
             if (shm_mq_get_sender(mq) == NULL)
             {
                 if (counterparty_gone)
                     return SHM_MQ_DETACHED;
                 else
                     return SHM_MQ_WOULD_BLOCK;
             }
         }
         else if (!shm_mq_wait_internal(mq, &mq->mq_sender, mqh->mqh_handle)
                  && shm_mq_get_sender(mq) == NULL)
         {
             mq->mq_detached = true;
             return SHM_MQ_DETACHED;
         }
         mqh->mqh_counterparty_attached = true;
     }
 
     /* Consume any zero-copy data from previous receive operation. */
     if (mqh->mqh_consume_pending > 0)
     {
         shm_mq_inc_bytes_read(mq, mqh->mqh_consume_pending);
         mqh->mqh_consume_pending = 0;
     }
 
     /* Try to read, or finish reading, the length word from the buffer. */
     while (!mqh->mqh_length_word_complete)
     {
         /* Try to receive the message length word. */
         Assert(mqh->mqh_partial_bytes < sizeof(Size));
         res = shm_mq_receive_bytes(mq, sizeof(Size) - mqh->mqh_partial_bytes,
                                    nowait, &rb, &rawdata);
         if (res != SHM_MQ_SUCCESS)
             return res;
 
         /*
          * Hopefully, we'll receive the entire message length word at once.
          * But if sizeof(Size) > MAXIMUM_ALIGNOF, then it might be split over
          * multiple reads.
          */
         if (mqh->mqh_partial_bytes == 0 && rb >= sizeof(Size))
         {
             Size        needed;
 
             nbytes = *(Size *) rawdata;
 
             /* If we've already got the whole message, we're done. */
             needed = MAXALIGN(sizeof(Size)) + MAXALIGN(nbytes);
             if (rb >= needed)
             {
                 /*
                  * Technically, we could consume the message length
                  * information at this point, but the extra write to shared
                  * memory wouldn't be free and in most cases we would reap no
                  * benefit.
                  */
                 mqh->mqh_consume_pending = needed;
                 *nbytesp = nbytes;
                 *datap = ((char *) rawdata) + MAXALIGN(sizeof(Size));
                 return SHM_MQ_SUCCESS;
             }
 
             /*
              * We don't have the whole message, but we at least have the whole
              * length word.
              */
             mqh->mqh_expected_bytes = nbytes;
             mqh->mqh_length_word_complete = true;
             shm_mq_inc_bytes_read(mq, MAXALIGN(sizeof(Size)));
             rb -= MAXALIGN(sizeof(Size));
         }
         else
         {
             Size        lengthbytes;
 
             /* Can't be split unless bigger than required alignment. */
             Assert(sizeof(Size) > MAXIMUM_ALIGNOF);
 
             /* Message word is split; need buffer to reassemble. */
             if (mqh->mqh_buffer == NULL)
             {
                 mqh->mqh_buffer = MemoryContextAlloc(mqh->mqh_context,
                                                      MQH_INITIAL_BUFSIZE);
                 mqh->mqh_buflen = MQH_INITIAL_BUFSIZE;
             }
             Assert(mqh->mqh_buflen >= sizeof(Size));
 
             /* Copy and consume partial length word. */
             if (mqh->mqh_partial_bytes + rb > sizeof(Size))
                 lengthbytes = sizeof(Size) - mqh->mqh_partial_bytes;
             else
                 lengthbytes = rb;
             memcpy(&mqh->mqh_buffer[mqh->mqh_partial_bytes], rawdata,
                    lengthbytes);
             mqh->mqh_partial_bytes += lengthbytes;
             shm_mq_inc_bytes_read(mq, MAXALIGN(lengthbytes));
             rb -= lengthbytes;
 
             /* If we now have the whole word, we're ready to read payload. */
             if (mqh->mqh_partial_bytes >= sizeof(Size))
             {
                 Assert(mqh->mqh_partial_bytes == sizeof(Size));
                 mqh->mqh_expected_bytes = *(Size *) mqh->mqh_buffer;
                 mqh->mqh_length_word_complete = true;
                 mqh->mqh_partial_bytes = 0;
             }
         }
     }
     nbytes = mqh->mqh_expected_bytes;
 
     if (mqh->mqh_partial_bytes == 0)
     {
         /*
          * Try to obtain the whole message in a single chunk.  If this works,
          * we need not copy the data and can return a pointer directly into
          * shared memory.
          */
         res = shm_mq_receive_bytes(mq, nbytes, nowait, &rb, &rawdata);
         if (res != SHM_MQ_SUCCESS)
             return res;
         if (rb >= nbytes)
         {
             mqh->mqh_length_word_complete = false;
             mqh->mqh_consume_pending = MAXALIGN(nbytes);
             *nbytesp = nbytes;
             *datap = rawdata;
             return SHM_MQ_SUCCESS;
         }
 
         /*
          * The message has wrapped the buffer.  We'll need to copy it in order
          * to return it to the client in one chunk.  First, make sure we have
          * a large enough buffer available.
          */
         if (mqh->mqh_buflen < nbytes)
         {
             Size        newbuflen = Max(mqh->mqh_buflen, MQH_INITIAL_BUFSIZE);
 
             while (newbuflen < nbytes)
                 newbuflen *= 2;
 
             if (mqh->mqh_buffer != NULL)
             {
                 pfree(mqh->mqh_buffer);
                 mqh->mqh_buffer = NULL;
                 mqh->mqh_buflen = 0;
             }
             mqh->mqh_buffer = MemoryContextAlloc(mqh->mqh_context, newbuflen);
             mqh->mqh_buflen = newbuflen;
         }
     }
 
     /* Loop until we've copied the entire message. */
     for (;;)
     {
         Size        still_needed;
 
         /* Copy as much as we can. */
         Assert(mqh->mqh_partial_bytes + rb <= nbytes);
         memcpy(&mqh->mqh_buffer[mqh->mqh_partial_bytes], rawdata, rb);
         mqh->mqh_partial_bytes += rb;
 
         /*
          * Update count of bytes read, with alignment padding.  Note that this
          * will never actually insert any padding except at the end of a
          * message, because the buffer size is a multiple of MAXIMUM_ALIGNOF,
          * and each read and write is as well.
          */
         Assert(mqh->mqh_partial_bytes == nbytes || rb == MAXALIGN(rb));
         shm_mq_inc_bytes_read(mq, MAXALIGN(rb));
 
         /* If we got all the data, exit the loop. */
         if (mqh->mqh_partial_bytes >= nbytes)
             break;
 
         /* Wait for some more data. */
         still_needed = nbytes - mqh->mqh_partial_bytes;
         res = shm_mq_receive_bytes(mq, still_needed, nowait, &rb, &rawdata);
         if (res != SHM_MQ_SUCCESS)
             return res;
         if (rb > still_needed)
             rb = still_needed;
     }
 
     /* Return the complete message, and reset for next message. */
     *nbytesp = nbytes;
     *datap = mqh->mqh_buffer;
     mqh->mqh_length_word_complete = false;
     mqh->mqh_partial_bytes = 0;
     return SHM_MQ_SUCCESS;
 }

shm_mq_result shm_mq_send	(	shm_mq_handle *	mqh,
		Size	nbytes,
		const void *	data,
		bool	nowait
	)

Definition at line 321 of file shm_mq.c.

References shm_mq_iovec::data, shm_mq_iovec::len, and shm_mq_sendv().

Referenced by copy_messages(), test_shm_mq(), test_shm_mq_pipelined(), TQSendRecordInfo(), and tqueueReceiveSlot().

 {
     shm_mq_iovec iov;
 
     iov.data = data;
     iov.len = nbytes;
 
     return shm_mq_sendv(mqh, &iov, 1, nowait);
 }

shm_mq_result shm_mq_sendv	(	shm_mq_handle *	mqh,
		shm_mq_iovec *	iov,
		int	iovcnt,
		bool	nowait
	)

Definition at line 347 of file shm_mq.c.

References Assert, shm_mq_iovec::data, i, shm_mq_iovec::len, MAXALIGN_DOWN, shm_mq::mq_sender, shm_mq_handle::mqh_length_word_complete, shm_mq_handle::mqh_partial_bytes, shm_mq_handle::mqh_queue, MyProc, SHM_MQ_DETACHED, shm_mq_notify_receiver(), shm_mq_send_bytes(), SHM_MQ_SUCCESS, and tmpbuf.

Referenced by mq_putmessage(), and shm_mq_send().

 {
     shm_mq_result res;
     shm_mq     *mq = mqh->mqh_queue;
     Size        nbytes = 0;
     Size        bytes_written;
     int         i;
     int         which_iov = 0;
     Size        offset;
 
     Assert(mq->mq_sender == MyProc);
 
     /* Compute total size of write. */
     for (i = 0; i < iovcnt; ++i)
         nbytes += iov[i].len;
 
     /* Try to write, or finish writing, the length word into the buffer. */
     while (!mqh->mqh_length_word_complete)
     {
         Assert(mqh->mqh_partial_bytes < sizeof(Size));
         res = shm_mq_send_bytes(mqh, sizeof(Size) - mqh->mqh_partial_bytes,
                                 ((char *) &nbytes) + mqh->mqh_partial_bytes,
                                 nowait, &bytes_written);
 
         if (res == SHM_MQ_DETACHED)
         {
             /* Reset state in case caller tries to send another message. */
             mqh->mqh_partial_bytes = 0;
             mqh->mqh_length_word_complete = false;
             return res;
         }
         mqh->mqh_partial_bytes += bytes_written;
 
         if (mqh->mqh_partial_bytes >= sizeof(Size))
         {
             Assert(mqh->mqh_partial_bytes == sizeof(Size));
 
             mqh->mqh_partial_bytes = 0;
             mqh->mqh_length_word_complete = true;
         }
 
         if (res != SHM_MQ_SUCCESS)
             return res;
 
         /* Length word can't be split unless bigger than required alignment. */
         Assert(mqh->mqh_length_word_complete || sizeof(Size) > MAXIMUM_ALIGNOF);
     }
 
     /* Write the actual data bytes into the buffer. */
     Assert(mqh->mqh_partial_bytes <= nbytes);
     offset = mqh->mqh_partial_bytes;
     do
     {
         Size        chunksize;
 
         /* Figure out which bytes need to be sent next. */
         if (offset >= iov[which_iov].len)
         {
             offset -= iov[which_iov].len;
             ++which_iov;
             if (which_iov >= iovcnt)
                 break;
             continue;
         }
 
         /*
          * We want to avoid copying the data if at all possible, but every
          * chunk of bytes we write into the queue has to be MAXALIGN'd, except
          * the last.  Thus, if a chunk other than the last one ends on a
          * non-MAXALIGN'd boundary, we have to combine the tail end of its
          * data with data from one or more following chunks until we either
          * reach the last chunk or accumulate a number of bytes which is
          * MAXALIGN'd.
          */
         if (which_iov + 1 < iovcnt &&
             offset + MAXIMUM_ALIGNOF > iov[which_iov].len)
         {
             char        tmpbuf[MAXIMUM_ALIGNOF];
             int         j = 0;
 
             for (;;)
             {
                 if (offset < iov[which_iov].len)
                 {
                     tmpbuf[j] = iov[which_iov].data[offset];
                     j++;
                     offset++;
                     if (j == MAXIMUM_ALIGNOF)
                         break;
                 }
                 else
                 {
                     offset -= iov[which_iov].len;
                     which_iov++;
                     if (which_iov >= iovcnt)
                         break;
                 }
             }
 
             res = shm_mq_send_bytes(mqh, j, tmpbuf, nowait, &bytes_written);
 
             if (res == SHM_MQ_DETACHED)
             {
                 /* Reset state in case caller tries to send another message. */
                 mqh->mqh_partial_bytes = 0;
                 mqh->mqh_length_word_complete = false;
                 return res;
             }
 
             mqh->mqh_partial_bytes += bytes_written;
             if (res != SHM_MQ_SUCCESS)
                 return res;
             continue;
         }
 
         /*
          * If this is the last chunk, we can write all the data, even if it
          * isn't a multiple of MAXIMUM_ALIGNOF.  Otherwise, we need to
          * MAXALIGN_DOWN the write size.
          */
         chunksize = iov[which_iov].len - offset;
         if (which_iov + 1 < iovcnt)
             chunksize = MAXALIGN_DOWN(chunksize);
         res = shm_mq_send_bytes(mqh, chunksize, &iov[which_iov].data[offset],
                                 nowait, &bytes_written);
 
         if (res == SHM_MQ_DETACHED)
         {
             /* Reset state in case caller tries to send another message. */
             mqh->mqh_length_word_complete = false;
             mqh->mqh_partial_bytes = 0;
             return res;
         }
 
         mqh->mqh_partial_bytes += bytes_written;
         offset += bytes_written;
         if (res != SHM_MQ_SUCCESS)
             return res;
     } while (mqh->mqh_partial_bytes < nbytes);
 
     /* Reset for next message. */
     mqh->mqh_partial_bytes = 0;
     mqh->mqh_length_word_complete = false;
 
     /* Notify receiver of the newly-written data, and return. */
     return shm_mq_notify_receiver(mq);
 }

void shm_mq_set_handle	(	shm_mq_handle *	,
		BackgroundWorkerHandle *
	)

Definition at line 311 of file shm_mq.c.

References Assert, shm_mq_handle::mqh_handle, and NULL.

Referenced by ExecGather(), ExecGatherMerge(), and LaunchParallelWorkers().

 {
     Assert(mqh->mqh_handle == NULL);
     mqh->mqh_handle = handle;
 }

void shm_mq_set_receiver	(	shm_mq *	mq,
		PGPROC *
	)

Definition at line 196 of file shm_mq.c.

References Assert, shm_mq::mq_mutex, shm_mq::mq_receiver, shm_mq::mq_sender, NULL, PGPROC::procLatch, SetLatch(), SpinLockAcquire, and SpinLockRelease.

Referenced by attach_to_queues(), ExecParallelSetupTupleQueues(), InitializeParallelDSM(), ReinitializeParallelDSM(), and setup_dynamic_shared_memory().

 {
     volatile shm_mq *vmq = mq;
     PGPROC     *sender;
 
     SpinLockAcquire(&mq->mq_mutex);
     Assert(vmq->mq_receiver == NULL);
     vmq->mq_receiver = proc;
     sender = vmq->mq_sender;
     SpinLockRelease(&mq->mq_mutex);
 
     if (sender != NULL)
         SetLatch(&sender->procLatch);
 }

void shm_mq_set_sender	(	shm_mq *	mq,
		PGPROC *
	)

Definition at line 215 of file shm_mq.c.

References Assert, shm_mq::mq_mutex, shm_mq::mq_receiver, shm_mq::mq_sender, NULL, PGPROC::procLatch, SetLatch(), SpinLockAcquire, and SpinLockRelease.

Referenced by attach_to_queues(), ExecParallelGetReceiver(), ParallelWorkerMain(), and setup_dynamic_shared_memory().

 {
     volatile shm_mq *vmq = mq;
     PGPROC     *receiver;
 
     SpinLockAcquire(&mq->mq_mutex);
     Assert(vmq->mq_sender == NULL);
     vmq->mq_sender = proc;
     receiver = vmq->mq_receiver;
     SpinLockRelease(&mq->mq_mutex);
 
     if (receiver != NULL)
         SetLatch(&receiver->procLatch);
 }

shm_mq_result shm_mq_wait_for_attach ( shm_mq_handle * mqh )

Definition at line 748 of file shm_mq.c.

References Assert, shm_mq::mq_receiver, shm_mq::mq_sender, shm_mq_handle::mqh_handle, shm_mq_handle::mqh_queue, MyProc, SHM_MQ_DETACHED, shm_mq_get_receiver(), shm_mq_get_sender(), SHM_MQ_SUCCESS, and shm_mq_wait_internal().

 {
     shm_mq     *mq = mqh->mqh_queue;
     PGPROC    **victim;
 
     if (shm_mq_get_receiver(mq) == MyProc)
         victim = &mq->mq_sender;
     else
     {
         Assert(shm_mq_get_sender(mq) == MyProc);
         victim = &mq->mq_receiver;
     }
 
     if (shm_mq_wait_internal(mq, victim, mqh->mqh_handle))
         return SHM_MQ_SUCCESS;
     else
         return SHM_MQ_DETACHED;
 }

Variable Documentation

PGDLLIMPORT const Size shm_mq_minimum_size

Definition at line 158 of file shm_mq.c.

Referenced by setup_dynamic_shared_memory().

Data Structures

Typedefs

Enumerations

Functions

Variables

Typedef Documentation

Enumeration Type Documentation

Function Documentation

Variable Documentation