On Sat, Aug 6, 2016 at 6:35 PM, Andreas Seltenreich <[email protected]> wrote:
> Michael Paquier writes:
>
>> Andreas, with the patch attached is the assertion still triggered?
>> [2. text/x-diff; base-backup-crash-v2.patch]
>
> I didn't observe the crashes since applying this patch. There should
> have been about five by the amount of fuzzing done.
I have reworked the patch, replacing those two booleans with a single
enum. That's definitely clearer. Also, I have added this patch to the
CF to not lose track of it:
https://commitfest.postgresql.org/10/731/
Horiguchi-san, I have added you as a reviewer as you provided some
input. I hope you don't mind.
--
Michael
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index f13f9c1..2b8c09c 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -460,6 +460,25 @@ typedef union WALInsertLockPadded
} WALInsertLockPadded;
/*
+ * State of an exclusive backup
+ *
+ * EXCLUSIVE_BACKUP_NONE means that there is no exclusive backup actually
+ * running, to be more precise pg_start_backup() is not being executed for
+ * an exclusive backup and there is exclusive backup in progress.
+ * EXCLUSIVE_BACKUP_STARTING means that pg_start_backup() is running and
+ * that is is not done yet.
+ * EXCLUSIVE_BACKUP_IN_PROGRESS means that pg_start_backup() has finished
+ * running and an exclusive backup is in progress. pg_stop_backup() is
+ * needed to finish it.
+ */
+typedef enum ExclusiveBackupState
+{
+ EXCLUSIVE_BACKUP_NONE = 0,
+ EXCLUSIVE_BACKUP_STARTING,
+ EXCLUSIVE_BACKUP_IN_PROGRESS
+} ExclusiveBackupState;
+
+/*
* Shared state data for WAL insertion.
*/
typedef struct XLogCtlInsert
@@ -500,13 +519,14 @@ typedef struct XLogCtlInsert
bool fullPageWrites;
/*
- * exclusiveBackup is true if a backup started with pg_start_backup() is
- * in progress, and nonExclusiveBackups is a counter indicating the number
+ * exclusiveBackupState is changed to EXCLUSIVE_BACKUP_STARTING for the
+ * duration of pg_start_backup(), then to EXCLUSIVE_BACKUP_IN_PROGRESS once
+ * it is done, and nonExclusiveBackups is a counter indicating the number
* of streaming base backups currently in progress. forcePageWrites is set
* to true when either of these is non-zero. lastBackupStart is the latest
* checkpoint redo location used as a starting point for an online backup.
*/
- bool exclusiveBackup;
+ ExclusiveBackupState exclusiveBackupState;
int nonExclusiveBackups;
XLogRecPtr lastBackupStart;
@@ -9833,7 +9853,7 @@ do_pg_start_backup(const char *backupidstr, bool fast, TimeLineID *starttli_p,
WALInsertLockAcquireExclusive();
if (exclusive)
{
- if (XLogCtl->Insert.exclusiveBackup)
+ if (XLogCtl->Insert.exclusiveBackupState != EXCLUSIVE_BACKUP_NONE)
{
WALInsertLockRelease();
ereport(ERROR,
@@ -9841,7 +9861,7 @@ do_pg_start_backup(const char *backupidstr, bool fast, TimeLineID *starttli_p,
errmsg("a backup is already in progress"),
errhint("Run pg_stop_backup() and try again.")));
}
- XLogCtl->Insert.exclusiveBackup = true;
+ XLogCtl->Insert.exclusiveBackupState = EXCLUSIVE_BACKUP_STARTING;
}
else
XLogCtl->Insert.nonExclusiveBackups++;
@@ -10096,7 +10116,7 @@ do_pg_start_backup(const char *backupidstr, bool fast, TimeLineID *starttli_p,
{
/*
* Check for existing backup label --- implies a backup is already
- * running. (XXX given that we checked exclusiveBackup above,
+ * running. (XXX given that we checked exclusiveBackupState above,
* maybe it would be OK to just unlink any such label file?)
*/
if (stat(BACKUP_LABEL_FILE, &stat_buf) != 0)
@@ -10178,6 +10198,16 @@ do_pg_start_backup(const char *backupidstr, bool fast, TimeLineID *starttli_p,
PG_END_ENSURE_ERROR_CLEANUP(pg_start_backup_callback, (Datum) BoolGetDatum(exclusive));
/*
+ * Mark that start phase has correctly finished for an exclusive backup.
+ */
+ if (exclusive)
+ {
+ WALInsertLockAcquireExclusive();
+ XLogCtl->Insert.exclusiveBackupState = EXCLUSIVE_BACKUP_IN_PROGRESS;
+ WALInsertLockRelease();
+ }
+
+ /*
* We're done. As a convenience, return the starting WAL location.
*/
if (starttli_p)
@@ -10195,8 +10225,8 @@ pg_start_backup_callback(int code, Datum arg)
WALInsertLockAcquireExclusive();
if (exclusive)
{
- Assert(XLogCtl->Insert.exclusiveBackup);
- XLogCtl->Insert.exclusiveBackup = false;
+ Assert(XLogCtl->Insert.exclusiveBackupState == EXCLUSIVE_BACKUP_STARTING);
+ XLogCtl->Insert.exclusiveBackupState = EXCLUSIVE_BACKUP_NONE;
}
else
{
@@ -10204,7 +10234,7 @@ pg_start_backup_callback(int code, Datum arg)
XLogCtl->Insert.nonExclusiveBackups--;
}
- if (!XLogCtl->Insert.exclusiveBackup &&
+ if (XLogCtl->Insert.exclusiveBackupState == EXCLUSIVE_BACKUP_NONE &&
XLogCtl->Insert.nonExclusiveBackups == 0)
{
XLogCtl->Insert.forcePageWrites = false;
@@ -10280,14 +10310,21 @@ do_pg_stop_backup(char *labelfile, bool waitforarchive, TimeLineID *stoptli_p)
WALInsertLockAcquireExclusive();
if (exclusive)
{
- if (!XLogCtl->Insert.exclusiveBackup)
+ if (XLogCtl->Insert.exclusiveBackupState == EXCLUSIVE_BACKUP_NONE)
{
WALInsertLockRelease();
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("exclusive backup not in progress")));
}
- XLogCtl->Insert.exclusiveBackup = false;
+ if (XLogCtl->Insert.exclusiveBackupState == EXCLUSIVE_BACKUP_STARTING)
+ {
+ WALInsertLockRelease();
+ ereport(ERROR,
+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+ errmsg("exclusive backup currently starting")));
+ }
+ XLogCtl->Insert.exclusiveBackupState = EXCLUSIVE_BACKUP_NONE;
}
else
{
@@ -10301,7 +10338,7 @@ do_pg_stop_backup(char *labelfile, bool waitforarchive, TimeLineID *stoptli_p)
XLogCtl->Insert.nonExclusiveBackups--;
}
- if (!XLogCtl->Insert.exclusiveBackup &&
+ if (XLogCtl->Insert.exclusiveBackupState == EXCLUSIVE_BACKUP_NONE &&
XLogCtl->Insert.nonExclusiveBackups == 0)
{
XLogCtl->Insert.forcePageWrites = false;
@@ -10597,7 +10634,7 @@ do_pg_abort_backup(void)
Assert(XLogCtl->Insert.nonExclusiveBackups > 0);
XLogCtl->Insert.nonExclusiveBackups--;
- if (!XLogCtl->Insert.exclusiveBackup &&
+ if (XLogCtl->Insert.exclusiveBackupState == EXCLUSIVE_BACKUP_NONE &&
XLogCtl->Insert.nonExclusiveBackups == 0)
{
XLogCtl->Insert.forcePageWrites = false;
--
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