On 2020-03-27 08:48, Michael Paquier wrote:
On Thu, Mar 26, 2020 at 02:16:05PM +0100, Peter Eisentraut wrote:
committed and backpatched
The patch committed does that in three places:
/* 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",
But why do you assume that LWLockRelease() never changes errno? It
seems to me that you should save errno before calling LWLockRelease(),
and then restore it back before using %m in the log message, no? See
for example the case where trace_lwlocks is set.
Good catch. How about the attached patch?
--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>From 484d734e9a985fa3e9242644ca9173658b9efe2c Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <pe...@eisentraut.org>
Date: Wed, 1 Apr 2020 16:24:47 +0200
Subject: [PATCH] Save errno across LWLockRelease() calls
Fixup for "Drop slot's LWLock before returning from SaveSlotToPath()"
Reported-by: Michael Paquier <mich...@paquier.xyz>
---
src/backend/replication/slot.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index d90c7235e9..47851ec4c1 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -1259,9 +1259,13 @@ SaveSlotToPath(ReplicationSlot *slot, const char *dir,
int elevel)
/*
* 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.
+ * lock, but no harm in explicitly releasing even in that case.
Note
+ * that LWLockRelease() could affect errno.
*/
+ int save_errno = errno;
+
LWLockRelease(&slot->io_in_progress_lock);
+ errno = save_errno;
ereport(elevel,
(errcode_for_file_access(),
errmsg("could not create file \"%s\": %m",
@@ -1325,7 +1329,10 @@ SaveSlotToPath(ReplicationSlot *slot, const char *dir,
int elevel)
if (CloseTransientFile(fd) != 0)
{
+ int save_errno = errno;
+
LWLockRelease(&slot->io_in_progress_lock);
+ errno = save_errno;
ereport(elevel,
(errcode_for_file_access(),
errmsg("could not close file \"%s\": %m",
@@ -1336,7 +1343,10 @@ SaveSlotToPath(ReplicationSlot *slot, const char *dir,
int elevel)
/* rename to permanent file, fsync file and directory */
if (rename(tmppath, path) != 0)
{
+ int save_errno = errno;
+
LWLockRelease(&slot->io_in_progress_lock);
+ errno = save_errno;
ereport(elevel,
(errcode_for_file_access(),
errmsg("could not rename file \"%s\" to
\"%s\": %m",
--
2.26.0
