From d34c03b034a8ac6d806468dde16810fadaa5cbcc Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Tue, 25 Aug 2026 19:00:58 +0300 Subject: [PATCH v2 1/3] Fix backend state after a failed after-startup shmem request RegisterShmemCallbacks() left the backend in a bad state, if an error occurred in the callbacks or if an allocation failed. Firstly, 'shmem_request_state' was left in wrong state, causing a subsequent call to RegisterShmemCallbacks() to wrongly take the postmaster startup codepath or assertion failures in some other functions. Secondly, the 'pending_shmem_requests' list was not properly cleaned up, causing a subsequent RegisterShmemCallbacks() to try to process the stale, already-freed requests. To fix, add a PG_TRY() block to clean those things up on error. Author: Ayush Tiwari Reviewed-by: Ashutosh Bapat Discussion: https://www.postgresql.org/message-id/CAJTYsWVRRWH48=PcuAo_2Y4Ap6M0QRmzxgUfFkNRtdWK74LjBQ@mail.gmail.com Backpatch-through: 19 --- src/backend/storage/ipc/shmem.c | 58 +++++++++++++++++++++------------ 1 file changed, 38 insertions(+), 20 deletions(-) diff --git a/src/backend/storage/ipc/shmem.c b/src/backend/storage/ipc/shmem.c index 228871d2525..0fadbf85a02 100644 --- a/src/backend/storage/ipc/shmem.c +++ b/src/backend/storage/ipc/shmem.c @@ -274,6 +274,7 @@ typedef struct static bool firstNumaTouch = true; static void CallShmemCallbacksAfterStartup(const ShmemCallbacks *callbacks); +static void ProcessShmemRequestsAfterStartup(const ShmemCallbacks *callbacks); static void InitShmemIndexEntry(ShmemRequest *request); static bool AttachShmemIndexEntry(ShmemRequest *request, bool missing_ok); @@ -897,26 +898,44 @@ RegisterShmemCallbacks(const ShmemCallbacks *callbacks) static void CallShmemCallbacksAfterStartup(const ShmemCallbacks *callbacks) { - bool found_any; - bool notfound_any; - Assert(shmem_request_state == SRS_DONE); - shmem_request_state = SRS_REQUESTING; - - /* - * Call the request callback first. The callback makes ShmemRequest*() - * calls for each shmem area, adding them to pending_shmem_requests. - */ Assert(pending_shmem_requests == NIL); - if (callbacks->request_fn) - callbacks->request_fn(callbacks->opaque_arg); - shmem_request_state = SRS_AFTER_STARTUP_ATTACH_OR_INIT; - if (pending_shmem_requests == NIL) + PG_TRY(); + { + /* + * Call the request callback first. The callback makes + * ShmemRequest*() calls for each shmem area, adding them to + * pending_shmem_requests. + */ + shmem_request_state = SRS_REQUESTING; + if (callbacks->request_fn) + callbacks->request_fn(callbacks->opaque_arg); + + /* Process all the requests */ + shmem_request_state = SRS_AFTER_STARTUP_ATTACH_OR_INIT; + if (pending_shmem_requests != NIL) + ProcessShmemRequestsAfterStartup(callbacks); + } + PG_FINALLY(); { shmem_request_state = SRS_DONE; - return; + pending_shmem_requests = NIL; } + PG_END_TRY(); +} + +static void +ProcessShmemRequestsAfterStartup(const ShmemCallbacks *callbacks) +{ + bool found_any; + bool notfound_any; + + /* There should be some requests to process */ + Assert(pending_shmem_requests != NIL); + + /* Caller manages the global state variable */ + Assert(shmem_request_state == SRS_AFTER_STARTUP_ATTACH_OR_INIT); /* * Hold ShmemIndexLock while we allocate all the shmem entries and run all @@ -934,7 +953,11 @@ CallShmemCallbacksAfterStartup(const ShmemCallbacks *callbacks) found_any = notfound_any = false; foreach_ptr(ShmemRequest, request, pending_shmem_requests) { - if (hash_search(ShmemIndex, request->options->name, HASH_FIND, NULL)) + ShmemIndexEnt *index_entry; + + index_entry = (ShmemIndexEnt *) + hash_search(ShmemIndex, request->options->name, HASH_FIND, NULL); + if (index_entry) found_any = true; else notfound_any = true; @@ -952,11 +975,7 @@ CallShmemCallbacksAfterStartup(const ShmemCallbacks *callbacks) AttachShmemIndexEntry(request, false); else InitShmemIndexEntry(request); - - pfree(request->options); } - list_free_deep(pending_shmem_requests); - pending_shmem_requests = NIL; /* Finish by calling the appropriate subsystem-specific callback */ if (found_any) @@ -971,7 +990,6 @@ CallShmemCallbacksAfterStartup(const ShmemCallbacks *callbacks) } LWLockRelease(ShmemIndexLock); - shmem_request_state = SRS_DONE; } /* -- 2.47.3