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Drop slot's LWLock before returning from SaveSlotToPath()

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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
This commit is contained in:
Peter Eisentraut 2020-03-26 11:51:39 +01:00
parent 58995db07e
commit ba4cc05ce2
1 changed files with 9 additions and 0 deletions
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9
src/backend/replication/slot.c
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@ -1257,6 +1257,12 @@ 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",
@ -1288,6 +1294,7 @@ 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;
@ -1307,6 +1314,7 @@ 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(),
@ -1321,6 +1329,7 @@ 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",