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Drop slot's LWLock before returning from SaveSlotToPath()

author Peter Eisentraut <peter@eisentraut.org>

2020年3月26日 10:51:39 +0000 (11:51 +0100)

committer Peter Eisentraut <peter@eisentraut.org>

2020年3月26日 12:31:07 +0000 (13:31 +0100)

When SaveSlotToPath() is called with elevel=LOG, the early exits didn't
release the slot's io_in_progress_lock.

This could result in a walsender being stuck on the lock forever. A
possible way to get into this situation is if the offending code paths
are triggered in a low disk space situation.

Author: Pavan Deolasee <pavan.deolasee@2ndquadrant.com>
Reported-by: Craig Ringer <craig@2ndquadrant.com>
Discussion: https://www.postgresql.org/message-id/flat/56a138c5-de61-f553-7e8f-6789296de785%402ndquadrant.com

src/backend/replication/slot.c patch | blob | blame | history

diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c

index f2fd8f336ed5e1a031782aa9c2b51d2518a5b09f..409db4b2eff2f52a91d2ee7d74cb35f18f4ead27 100644 (file)

--- a/src/backend/replication/slot.c

+++ b/src/backend/replication/slot.c

@@ -1256,6 +1256,12 @@ SaveSlotToPath(ReplicationSlot *slot, const char *dir, int elevel)

fd = OpenTransientFile(tmppath, O_CREAT | O_EXCL | O_WRONLY | PG_BINARY);

if (fd < 0)

{

+ /*

+ * If not an ERROR, then release the lock before returning. In case

+ * of an ERROR, the error recovery path automatically releases the

+ * lock, but no harm in explicitly releasing even in that case.

+ */

+ LWLockRelease(&slot->io_in_progress_lock);

ereport(elevel,

(errcode_for_file_access(),

errmsg("could not create file \"%s\": %m",

@@ -1287,6 +1293,7 @@ SaveSlotToPath(ReplicationSlot *slot, const char *dir, int elevel)

pgstat_report_wait_end();

CloseTransientFile(fd);

+ LWLockRelease(&slot->io_in_progress_lock);

/* if write didn't set errno, assume problem is no disk space */

errno = save_errno ? save_errno : ENOSPC;

@@ -1306,6 +1313,7 @@ SaveSlotToPath(ReplicationSlot *slot, const char *dir, int elevel)

pgstat_report_wait_end();

CloseTransientFile(fd);

+ LWLockRelease(&slot->io_in_progress_lock);

errno = save_errno;

ereport(elevel,

(errcode_for_file_access(),

@@ -1317,6 +1325,7 @@ SaveSlotToPath(ReplicationSlot *slot, const char *dir, int elevel)

if (CloseTransientFile(fd))

{

+ LWLockRelease(&slot->io_in_progress_lock);

ereport(elevel,

(errcode_for_file_access(),

errmsg("could not close file \"%s\": %m",

@@ -1327,6 +1336,7 @@ SaveSlotToPath(ReplicationSlot *slot, const char *dir, int elevel)

/* rename to permanent file, fsync file and directory */

if (rename(tmppath, path) != 0)

{

+ LWLockRelease(&slot->io_in_progress_lock);

ereport(elevel,

(errcode_for_file_access(),

errmsg("could not rename file \"%s\" to \"%s\": %m",

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