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authorTom Lane2009-05-05 19:59:00 +0000
committerTom Lane2009-05-05 19:59:00 +0000
commit969d7cd4315bfe30aed5221b69ee34e7cd132789 (patch)
tree958e2b4b6332c01c0e2adee52a79653e5c588a13 /src/include/miscadmin.h
parent8f348112f35d9dcc28fc575f8bae458883c5700a (diff)
Install a "dead man switch" to allow the postmaster to detect cases where
a backend has done exit(0) or exit(1) without having disengaged itself from shared memory. We are at risk for this whenever third-party code is loaded into a backend, since such code might not know it's supposed to go through proc_exit() instead. Also, it is reported that under Windows there are ways to externally kill a process that cause the status code returned to the postmaster to be indistinguishable from a voluntary exit (thank you, Microsoft). If this does happen then the system is probably hosed --- for instance, the dead session might still be holding locks. So the best recovery method is to treat this like a backend crash. The dead man switch is armed for a particular child process when it acquires a regular PGPROC, and disarmed when the PGPROC is released; these should be the first and last touches of shared memory resources in a backend, or close enough anyway. This choice means there is no coverage for auxiliary processes, but I doubt we need that, since they shouldn't be executing any user-provided code anyway. This patch also improves the management of the EXEC_BACKEND ShmemBackendArray array a bit, by reducing search costs. Although this problem is of long standing, the lack of field complaints seems to mean it's not critical enough to risk back-patching; at least not till we get some more testing of this mechanism.
Diffstat (limited to 'src/include/miscadmin.h')
-rw-r--r--src/include/miscadmin.h3
1 files changed, 2 insertions, 1 deletions
diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
index 57ee0f93dd4..51649380d51 100644
--- a/src/include/miscadmin.h
+++ b/src/include/miscadmin.h
@@ -13,7 +13,7 @@
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/miscadmin.h,v 1.209 2009/01/05 02:27:45 alvherre Exp $
+ * $PostgreSQL: pgsql/src/include/miscadmin.h,v 1.210 2009/05/05 19:59:00 tgl Exp $
*
* NOTES
* some of the information in this file should be moved to other files.
@@ -137,6 +137,7 @@ extern PGDLLIMPORT int MyProcPid;
extern PGDLLIMPORT pg_time_t MyStartTime;
extern PGDLLIMPORT struct Port *MyProcPort;
extern long MyCancelKey;
+extern int MyPMChildSlot;
extern char OutputFileName[];
extern PGDLLIMPORT char my_exec_path[];