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Commit44339b8

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shm_mq: After a send fails with SHM_MQ_DETACHED, later ones should too.
Prior to this patch, it was occasionally possible, after shm_mq_sendvhad previously returned SHM_MQ_DETACHED, for a later shm_mq_sendvoperation to fail an assertion instead of just again returningSHM_MQ_ATTACHED. From the shm_mq code's point of view, it wasexpecting to be called again with the same arguments, since theprevious operation had only partially completed. However, a callerwho isn't using non-blocking mode won't be prepared to repeat the callwith the same arguments, and this code shouldn't expect that theywill. Repair in such a way that we'll be OK whether the next calluses the same arguments or not.Found by Andreas Seltenreich. Analysis and sketch of fix by AmitKapila. Patch by me, reviewed by Amit Kapila.
1 parente191a69 commit44339b8

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‎src/backend/storage/ipc/shm_mq.c

Lines changed: 30 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -366,9 +366,15 @@ shm_mq_sendv(shm_mq_handle *mqh, shm_mq_iovec *iov, int iovcnt, bool nowait)
366366
res=shm_mq_send_bytes(mqh,sizeof(Size)-mqh->mqh_partial_bytes,
367367
((char*)&nbytes)+mqh->mqh_partial_bytes,
368368
nowait,&bytes_written);
369-
mqh->mqh_partial_bytes+=bytes_written;
370-
if (res!=SHM_MQ_SUCCESS)
369+
370+
if (res==SHM_MQ_DETACHED)
371+
{
372+
/* Reset state in case caller tries to send another message. */
373+
mqh->mqh_partial_bytes=0;
374+
mqh->mqh_length_word_complete= false;
371375
returnres;
376+
}
377+
mqh->mqh_partial_bytes+=bytes_written;
372378

373379
if (mqh->mqh_partial_bytes >=sizeof(Size))
374380
{
@@ -378,6 +384,9 @@ shm_mq_sendv(shm_mq_handle *mqh, shm_mq_iovec *iov, int iovcnt, bool nowait)
378384
mqh->mqh_length_word_complete= true;
379385
}
380386

387+
if (res!=SHM_MQ_SUCCESS)
388+
returnres;
389+
381390
/* Length word can't be split unless bigger than required alignment. */
382391
Assert(mqh->mqh_length_word_complete||sizeof(Size)>MAXIMUM_ALIGNOF);
383392
}
@@ -432,7 +441,17 @@ shm_mq_sendv(shm_mq_handle *mqh, shm_mq_iovec *iov, int iovcnt, bool nowait)
432441
break;
433442
}
434443
}
444+
435445
res=shm_mq_send_bytes(mqh,j,tmpbuf,nowait,&bytes_written);
446+
447+
if (res==SHM_MQ_DETACHED)
448+
{
449+
/* Reset state in case caller tries to send another message. */
450+
mqh->mqh_partial_bytes=0;
451+
mqh->mqh_length_word_complete= false;
452+
returnres;
453+
}
454+
436455
mqh->mqh_partial_bytes+=bytes_written;
437456
if (res!=SHM_MQ_SUCCESS)
438457
returnres;
@@ -449,6 +468,15 @@ shm_mq_sendv(shm_mq_handle *mqh, shm_mq_iovec *iov, int iovcnt, bool nowait)
449468
chunksize=MAXALIGN_DOWN(chunksize);
450469
res=shm_mq_send_bytes(mqh,chunksize,&iov[which_iov].data[offset],
451470
nowait,&bytes_written);
471+
472+
if (res==SHM_MQ_DETACHED)
473+
{
474+
/* Reset state in case caller tries to send another message. */
475+
mqh->mqh_length_word_complete= false;
476+
mqh->mqh_partial_bytes=0;
477+
returnres;
478+
}
479+
452480
mqh->mqh_partial_bytes+=bytes_written;
453481
offset+=bytes_written;
454482
if (res!=SHM_MQ_SUCCESS)

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