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Commite921546

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Fix attach-related race condition in shm_mq_send_bytes.

Spotted by Antonin Houska.

1 parent8c7bb02 commite921546Copy full SHA for e921546

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1 file changed

+21

-17

lines changed

src/backend/storage/ipc
- shm_mq.c

1 file changed

+21

-17

lines changed

`‎src/backend/storage/ipc/shm_mq.c`

Lines changed: 21 additions & 17 deletions

Original file line number	Diff line number	Diff line change
`@@ -681,33 +681,37 @@ shm_mq_send_bytes(shm_mq_handle mqh, Size nbytes, void data, bool nowait,`
`681`	`681`	`returnSHM_MQ_DETACHED;`
`682`	`682`	`}`
`683`	`683`
`684`		`-if (available==0)`
	`684`	`+if (available==0&& !mqh->mqh_counterparty_attached)`
`685`	`685`	`{`
`686`		`-shm_mq_resultres;`
`687`		`-`
`688`	`686`	`/*`
`689`	`687`	`* The queue is full, so if the receiver isn't yet known to be`
`690`	`688`	`* attached, we must wait for that to happen.`
`691`	`689`	`*/`
`692`		`-if (!mqh->mqh_counterparty_attached)`
	`690`	`+if (nowait)`
`693`	`691`	`{`
`694`		`-if (nowait)`
	`692`	`+if (shm_mq_get_receiver(mq)==NULL)`
`695`	`693`	`{`
`696`		`-if (shm_mq_get_receiver(mq)==NULL)`
`697`		`-{`
`698`		`-*bytes_written=sent;`
`699`		`-returnSHM_MQ_WOULD_BLOCK;`
`700`		`-}`
`701`		`-}`
`702`		`-elseif (!shm_mq_wait_internal(mq,&mq->mq_receiver,`
`703`		`-mqh->mqh_handle))`
`704`		`-{`
`705`		`-mq->mq_detached= true;`
`706`	`694`	`*bytes_written=sent;`
`707`		`-returnSHM_MQ_DETACHED;`
	`695`	`+returnSHM_MQ_WOULD_BLOCK;`
`708`	`696`	`}`
`709`		`-mqh->mqh_counterparty_attached= true;`
`710`	`697`	`}`
	`698`	`+elseif (!shm_mq_wait_internal(mq,&mq->mq_receiver,`
	`699`	`+mqh->mqh_handle))`
	`700`	`+{`
	`701`	`+mq->mq_detached= true;`
	`702`	`+*bytes_written=sent;`
	`703`	`+returnSHM_MQ_DETACHED;`
	`704`	`+}`
	`705`	`+mqh->mqh_counterparty_attached= true;`
	`706`	`+`
	`707`	`+/*`
	`708`	`+ * The receiver may have read some data after attaching, so we`
	`709`	`+ * must not wait without rechecking the queue state.`
	`710`	`+ */`
	`711`	`+}`
	`712`	`+elseif (available==0)`
	`713`	`+{`
	`714`	`+shm_mq_resultres;`
`711`	`715`
`712`	`716`	`/* Let the receiver know that we need them to read some data. */`
`713`	`717`	`res=shm_mq_notify_receiver(mq);`

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Commite921546

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`‎src/backend/storage/ipc/shm_mq.c`

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