Fix Pgpool-II child process crash during shutdown.

It is reported that pgpool child process crashes during shutdown.
 [pgpool-general: 9261] Re: Segmentation fault during shutdown

The actual crash was in close_all_backend_connections().
close_all_backend_connections() was called because on_system_exit
registers child_will_ho_down(). At the moment it seems pgpool child
had just started up and doing pool_init_cp(). The connection pool
object had not been completely initialized, that's cause of the crash.

To fix this, just remove the call to close_all_backend_connections()
in child_will_ho_down(). Although this will prevent the terminate
message ('X') being sent to backend, it should be harmless since
backend can take care such a disconnection without a terminate
message.

Problem reported and analyzed by: Emond Papegaaij
Backpatch-through: v4.2
Discussion: https://www.pgpool.net/pipermail/pgpool-general/2024-November/001938.html

diff --git a/src/protocol/child.c b/src/protocol/child.c
index c12a5a2c1b2deef8b99e6e980e3879678f6d84c4..4e2a3443bf32ab9a700361339563915f90591874 100644 (file)
--- a/src/protocol/child.c
+++ b/src/protocol/child.c
@@ -1350,9 +1350,12 @@ child_will_go_down(int code, Datum arg)
                memcached_disconnect();
        }
 
-       /* let backend know now we are exiting */
-       if (pool_connection_pool)
-               close_all_backend_connections();
+       /*
+        * We used to call close_all_backend_connections() here so that we send
+        * 'X' (terminate) message to backend. However it was possible that the
+        * function is called while initializing the connection pool object, which
+        * leads to crash. So we stopped to call close_all_backend_connections().
+        */
 }
 
 /*