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commit    eb144dfcafdd7fcce817c75db0c353667b819e11
Author:   Michael Paquier <michael@paquier.xyz>
Date:     Thu Jun 27 00:44:55 2024 +0000

    Fix overflow with pgstats DSA reference count
    
    When pgstats is initialized for a backend, it uses dsa_attach_in_place()
    without a "segment" provided.  Hence, no callback is registered to
    automatically release the DSA attached once a backend exits.  Not doing
    any cleanup causes the reference count of the pgstats DSA to
    continuously increment, at some point overflowing it (the more the
    number of connections, the faster it is to reach this state).  Once the
    reference count overflows and then gets back to 0, new backends are not
    able to attach to the pgstats DSA, failing startup.
    
    This issue is resolved by adding in the pgstats shutdown hook a call to
    dsa_release_in_place(), ensuring that the DSA attached at backend
    startup is correctly released, keeping the reference count at bay.
    
    The author of this patch has been able to see this issue on a server
    with a long uptime and a high connection turnover.
    
    Issue introduced by 5891c7a8ed8f, so backpatch down to 15.
    
    Author: Anthonin Bonnefoy
    Discussion: https://postgr.es/m/CAO6_XqqJbJBL=M7Ym13TcB4Xnq58vRa2jcC+gwEPBgbAda6B1Q@mail.gmail.com
    Backpatch-through: 15


 src/backend/utils/activity/pgstat_shmem.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/backend/utils/activity/pgstat_shmem.c b/src/backend/utils/activity/pgstat_shmem.c
index cee0bd60234..2b6c7a07f88 100644
--- a/src/backend/utils/activity/pgstat_shmem.c
+++ b/src/backend/utils/activity/pgstat_shmem.c
@@ -241,6 +241,14 @@ pgstat_detach_shmem(void)
 	pgStatLocal.shared_hash = NULL;
 
 	dsa_detach(pgStatLocal.dsa);
+
+	/*
+	 * dsa_detach() does not decrement the DSA reference count as no segment
+	 * was provided to dsa_attach_in_place(), causing no cleanup callbacks to
+	 * be registered.  Hence, release it manually now.
+	 */
+	dsa_release_in_place(pgStatLocal.shmem->raw_dsa_area);
+
 	pgStatLocal.dsa = NULL;
 }
 


[parent: c809a2b2d68c]