Save errno across LWLockRelease() calls

Fixup for "Drop slot's LWLock before returning from SaveSlotToPath()"

Reported-by: Michael Paquier 

diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index d90c7235e986f52341744b04202cb55a7e4c1f82..47851ec4c1a9945db2f8366d634ccc0fbd16d81e 100644 (file)
--- 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",