From 239b1753421ccbd52f4f628a9265c3034d38b80f Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Wed, 25 Jan 2023 14:28:01 +1300 Subject: [PATCH] Process pending postmaster work before connections. Modify the new event loop code from commit 7389aad6 so that it checks for work requested by signal handlers even if it doesn't see a latch event yet. This gives priority to shutdown and reload requests where the latch will be reported later in the event array, or in a later call to WaitEventSetWait(), due to scheduling details. In particular, this guarantees that a SIGHUP-then-connect sequence (as seen in authentication tests) causes the postmaster to process the reload before accepting the connection. If the WaitEventSetWait() call saw the socket as ready, and the reload signal was generated before the connection, then the latest time the signal handler should be able to run is after poll/epoll_wait/kevent returns but before we check the pending_pm_reload_request flag. While here, also shift the handling of child exit below reload requests, per Tom Lane's observation that that might start new processes, so we should make sure we pick up new settings first. This probably explains the one-off failure of build farm animal malleefowl. Reported-by: Hou Zhijie Reported-by: Tom Lane Discussion: https://postgr.es/m/OS0PR01MB57163D3BF2AB42ECAA94E5C394C29%40OS0PR01MB5716.jpnprd01.prod.outlook.com --- src/backend/postmaster/postmaster.c | 29 +++++++++++++++++------------ 1 file changed, 17 insertions(+), 12 deletions(-) diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c index 711efc35e3..5b775cf7d0 100644 --- a/src/backend/postmaster/postmaster.c +++ b/src/backend/postmaster/postmaster.c @@ -1750,20 +1750,25 @@ ServerLoop(void) for (int i = 0; i < nevents; i++) { if (events[i].events & WL_LATCH_SET) - { ResetLatch(MyLatch); - /* Process work requested via signal handlers. */ - if (pending_pm_shutdown_request) - process_pm_shutdown_request(); - if (pending_pm_child_exit) - process_pm_child_exit(); - if (pending_pm_reload_request) - process_pm_reload_request(); - if (pending_pm_pmsignal) - process_pm_pmsignal(); - } - else if (events[i].events & WL_SOCKET_ACCEPT) + /* + * The following requests are handled unconditionally, even if we + * didn't see WL_LATCH_SET. This gives high priority to shutdown + * and reload requests where the latch happens to appear later in + * events[] or will be reported by a later call to + * WaitEventSetWait(). + */ + if (pending_pm_shutdown_request) + process_pm_shutdown_request(); + if (pending_pm_reload_request) + process_pm_reload_request(); + if (pending_pm_child_exit) + process_pm_child_exit(); + if (pending_pm_pmsignal) + process_pm_pmsignal(); + + if (events[i].events & WL_SOCKET_ACCEPT) { Port *port;