Teach on_exit_reset() to discard pending cleanups for dsm.

If a postmaster child invokes fork() and then calls on_exit_reset, that
should be sufficient to let it exit() without breaking anything, but
dynamic shared memory broke that by not updating on_exit_reset() to
discard callbacks registered with dynamic shared memory segments.

Per investigation of a complaint from Tom Lane.

diff --git a/src/backend/storage/ipc/dsm.c b/src/backend/storage/ipc/dsm.c
index 327d6850971af4a19e3ea2c25c38a99a6149dcd7..31e592e06e7b74d1f5da052424110c9eb0fe3770 100644 (file)
--- a/src/backend/storage/ipc/dsm.c
+++ b/src/backend/storage/ipc/dsm.c
@@ -979,6 +979,37 @@ cancel_on_dsm_detach(dsm_segment *seg, on_dsm_detach_callback function,
        }
 }
 
+/*
+ * Discard all registered on-detach callbacks without executing them.
+ */
+void
+reset_on_dsm_detach(void)
+{
+       dlist_iter              iter;
+
+       dlist_foreach(iter, &dsm_segment_list)
+       {
+               dsm_segment *seg = dlist_container(dsm_segment, node, iter.cur);
+
+               /* Throw away explicit on-detach actions one by one. */
+               while (!slist_is_empty(&seg->on_detach))
+               {
+                       slist_node *node;
+                       dsm_segment_detach_callback *cb;
+
+                       node = slist_pop_head_node(&seg->on_detach);
+                       cb = slist_container(dsm_segment_detach_callback, node, node);
+                       pfree(cb);
+               }
+
+               /*
+                * Decrementing the reference count is a sort of implicit on-detach
+                * action; make sure we don't do that, either.
+                */
+               seg->control_slot = INVALID_CONTROL_SLOT;
+       }
+}
+
 /*
  * Create a segment descriptor.
  */

diff --git a/src/backend/storage/ipc/ipc.c b/src/backend/storage/ipc/ipc.c
index 9dc48c30b611c5bf7550322a86d80ad2bc31e70f..5dea0ed8ddb3d646c2eadddf65346b988755f36f 100644 (file)
--- a/src/backend/storage/ipc/ipc.c
+++ b/src/backend/storage/ipc/ipc.c
@@ -400,4 +400,5 @@ on_exit_reset(void)
        before_shmem_exit_index = 0;
        on_shmem_exit_index = 0;
        on_proc_exit_index = 0;
+       reset_on_dsm_detach();
 }

diff --git a/src/include/storage/dsm.h b/src/include/storage/dsm.h
index 71901bf8c5acff7a87762770fc51953385a2eb98..46d3cbdd8ab6cd6ba576ef86b611025b8eec404d 100644 (file)
--- a/src/include/storage/dsm.h
+++ b/src/include/storage/dsm.h
@@ -43,5 +43,6 @@ extern void on_dsm_detach(dsm_segment *seg,
                          on_dsm_detach_callback function, Datum arg);
 extern void cancel_on_dsm_detach(dsm_segment *seg,
                          on_dsm_detach_callback function, Datum arg);
+extern void reset_on_dsm_detach(void);
 
 #endif   /* DSM_H */