From 44fc6e259b799f9924de206eeddc1b1fcbcd172f Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Wed, 16 Sep 2020 16:04:36 -0400 Subject: [PATCH] Centralize setup of SIGQUIT handling for postmaster child processes. We decided that the policy established in commit 7634bd4f6 for the bgwriter, checkpointer, walwriter, and walreceiver processes, namely that they should accept SIGQUIT at all times, really ought to apply uniformly to all postmaster children. Therefore, get rid of the duplicative and inconsistent per-process code for establishing that signal handler and removing SIGQUIT from BlockSig. Instead, make InitPostmasterChild do it. The handler set up by InitPostmasterChild is SignalHandlerForCrashExit, which just summarily does _exit(2). In interactive backends, we almost immediately replace that with quickdie, since we would prefer to try to tell the client that we're dying. However, this patch is changing the behavior of autovacuum (both launcher and workers), as well as walsenders. Those processes formerly also used quickdie, but AFAICS that was just mindless copy-and-paste: they don't have any interactive client that's likely to benefit from being told this. The stats collector continues to be an outlier, in that it thinks SIGQUIT means normal exit. That should probably be changed for consistency, but there's another patch set where that's being dealt with, so I didn't do so here. Discussion: https://postgr.es/m/644875.1599933441@sss.pgh.pa.us --- src/backend/postmaster/autovacuum.c | 18 ++++++++++-------- src/backend/postmaster/bgworker.c | 2 +- src/backend/postmaster/bgwriter.c | 6 +----- src/backend/postmaster/checkpointer.c | 6 +----- src/backend/postmaster/pgarch.c | 2 +- src/backend/postmaster/postmaster.c | 8 ++------ src/backend/postmaster/startup.c | 2 +- src/backend/postmaster/walwriter.c | 6 +----- src/backend/replication/walreceiver.c | 6 +----- src/backend/replication/walsender.c | 2 +- src/backend/tcop/postgres.c | 16 +++++----------- src/backend/utils/init/miscinit.c | 26 ++++++++++++++++++++++++++ 12 files changed, 51 insertions(+), 49 deletions(-) diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c index 19ba26b914..2cef56f115 100644 --- a/src/backend/postmaster/autovacuum.c +++ b/src/backend/postmaster/autovacuum.c @@ -454,8 +454,8 @@ AutoVacLauncherMain(int argc, char *argv[]) pqsignal(SIGHUP, SignalHandlerForConfigReload); pqsignal(SIGINT, StatementCancelHandler); pqsignal(SIGTERM, SignalHandlerForShutdownRequest); + /* SIGQUIT handler was already set up by InitPostmasterChild */ - pqsignal(SIGQUIT, quickdie); InitializeTimeouts(); /* establishes SIGALRM handler */ pqsignal(SIGPIPE, SIG_IGN); @@ -498,9 +498,10 @@ AutoVacLauncherMain(int argc, char *argv[]) * * Note that we use sigsetjmp(..., 1), so that the prevailing signal mask * (to wit, BlockSig) will be restored when longjmp'ing to here. Thus, - * signals will be blocked until we complete error recovery. It might - * seem that this policy makes the HOLD_INTERRUPTS() call redundant, but - * it is not since InterruptPending might be set already. + * signals other than SIGQUIT will be blocked until we complete error + * recovery. It might seem that this policy makes the HOLD_INTERRUPTS() + * call redundant, but it is not since InterruptPending might be set + * already. */ if (sigsetjmp(local_sigjmp_buf, 1) != 0) { @@ -1531,7 +1532,8 @@ AutoVacWorkerMain(int argc, char *argv[]) */ pqsignal(SIGINT, StatementCancelHandler); pqsignal(SIGTERM, die); - pqsignal(SIGQUIT, quickdie); + /* SIGQUIT handler was already set up by InitPostmasterChild */ + InitializeTimeouts(); /* establishes SIGALRM handler */ pqsignal(SIGPIPE, SIG_IGN); @@ -1562,9 +1564,9 @@ AutoVacWorkerMain(int argc, char *argv[]) * * Note that we use sigsetjmp(..., 1), so that the prevailing signal mask * (to wit, BlockSig) will be restored when longjmp'ing to here. Thus, - * signals will be blocked until we exit. It might seem that this policy - * makes the HOLD_INTERRUPTS() call redundant, but it is not since - * InterruptPending might be set already. + * signals other than SIGQUIT will be blocked until we exit. It might + * seem that this policy makes the HOLD_INTERRUPTS() call redundant, but + * it is not since InterruptPending might be set already. */ if (sigsetjmp(local_sigjmp_buf, 1) != 0) { diff --git a/src/backend/postmaster/bgworker.c b/src/backend/postmaster/bgworker.c index d043ced686..5a9a0e3435 100644 --- a/src/backend/postmaster/bgworker.c +++ b/src/backend/postmaster/bgworker.c @@ -731,9 +731,9 @@ StartBackgroundWorker(void) pqsignal(SIGFPE, SIG_IGN); } pqsignal(SIGTERM, bgworker_die); + /* SIGQUIT handler was already set up by InitPostmasterChild */ pqsignal(SIGHUP, SIG_IGN); - pqsignal(SIGQUIT, SignalHandlerForCrashExit); InitializeTimeouts(); /* establishes SIGALRM handler */ pqsignal(SIGPIPE, SIG_IGN); diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index c96568149f..a7afa758b6 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -104,7 +104,7 @@ BackgroundWriterMain(void) pqsignal(SIGHUP, SignalHandlerForConfigReload); pqsignal(SIGINT, SIG_IGN); pqsignal(SIGTERM, SignalHandlerForShutdownRequest); - pqsignal(SIGQUIT, SignalHandlerForCrashExit); + /* SIGQUIT handler was already set up by InitPostmasterChild */ pqsignal(SIGALRM, SIG_IGN); pqsignal(SIGPIPE, SIG_IGN); pqsignal(SIGUSR1, procsignal_sigusr1_handler); @@ -115,10 +115,6 @@ BackgroundWriterMain(void) */ pqsignal(SIGCHLD, SIG_DFL); - /* We allow SIGQUIT (SignalHandlerForCrashExit) at all times */ - sigdelset(&BlockSig, SIGQUIT); - PG_SETMASK(&BlockSig); - /* * We just started, assume there has been either a shutdown or * end-of-recovery snapshot. diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c index 45f5deca72..3e7dcd4f76 100644 --- a/src/backend/postmaster/checkpointer.c +++ b/src/backend/postmaster/checkpointer.c @@ -198,7 +198,7 @@ CheckpointerMain(void) pqsignal(SIGHUP, SignalHandlerForConfigReload); pqsignal(SIGINT, ReqCheckpointHandler); /* request checkpoint */ pqsignal(SIGTERM, SIG_IGN); /* ignore SIGTERM */ - pqsignal(SIGQUIT, SignalHandlerForCrashExit); + /* SIGQUIT handler was already set up by InitPostmasterChild */ pqsignal(SIGALRM, SIG_IGN); pqsignal(SIGPIPE, SIG_IGN); pqsignal(SIGUSR1, procsignal_sigusr1_handler); @@ -209,10 +209,6 @@ CheckpointerMain(void) */ pqsignal(SIGCHLD, SIG_DFL); - /* We allow SIGQUIT (SignalHandlerForCrashExit) at all times */ - sigdelset(&BlockSig, SIGQUIT); - PG_SETMASK(&BlockSig); - /* * Initialize so that first time-driven event happens at the correct time. */ diff --git a/src/backend/postmaster/pgarch.c b/src/backend/postmaster/pgarch.c index 37be0e2bbb..ed1b65358d 100644 --- a/src/backend/postmaster/pgarch.c +++ b/src/backend/postmaster/pgarch.c @@ -228,7 +228,7 @@ PgArchiverMain(int argc, char *argv[]) pqsignal(SIGHUP, SignalHandlerForConfigReload); pqsignal(SIGINT, SIG_IGN); pqsignal(SIGTERM, SignalHandlerForShutdownRequest); - pqsignal(SIGQUIT, SignalHandlerForCrashExit); + /* SIGQUIT handler was already set up by InitPostmasterChild */ pqsignal(SIGALRM, SIG_IGN); pqsignal(SIGPIPE, SIG_IGN); pqsignal(SIGUSR1, pgarch_waken); diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c index 3cd6fa30eb..959e3b8873 100644 --- a/src/backend/postmaster/postmaster.c +++ b/src/backend/postmaster/postmaster.c @@ -4355,7 +4355,7 @@ BackendInitialize(Port *port) * cleaned up. */ pqsignal(SIGTERM, process_startup_packet_die); - pqsignal(SIGQUIT, SignalHandlerForCrashExit); + /* SIGQUIT handler was already set up by InitPostmasterChild */ InitializeTimeouts(); /* establishes SIGALRM handler */ PG_SETMASK(&StartupBlockSig); @@ -4435,7 +4435,7 @@ BackendInitialize(Port *port) status = ProcessStartupPacket(port, false, false); /* - * Disable the timeout, and prevent SIGTERM/SIGQUIT again. + * Disable the timeout, and prevent SIGTERM again. */ disable_timeout(STARTUP_PACKET_TIMEOUT, false); PG_SETMASK(&BlockSig); @@ -4983,10 +4983,6 @@ SubPostmasterMain(int argc, char *argv[]) if (strcmp(argv[1], "--forkavworker") == 0) AutovacuumWorkerIAm(); - /* In EXEC_BACKEND case we will not have inherited these settings */ - pqinitmask(); - PG_SETMASK(&BlockSig); - /* Read in remaining GUC variables */ read_nondefault_variables(); diff --git a/src/backend/postmaster/startup.c b/src/backend/postmaster/startup.c index fd9ac35dac..64af7b8707 100644 --- a/src/backend/postmaster/startup.c +++ b/src/backend/postmaster/startup.c @@ -175,7 +175,7 @@ StartupProcessMain(void) pqsignal(SIGHUP, StartupProcSigHupHandler); /* reload config file */ pqsignal(SIGINT, SIG_IGN); /* ignore query cancel */ pqsignal(SIGTERM, StartupProcShutdownHandler); /* request shutdown */ - pqsignal(SIGQUIT, SignalHandlerForCrashExit); + /* SIGQUIT handler was already set up by InitPostmasterChild */ InitializeTimeouts(); /* establishes SIGALRM handler */ pqsignal(SIGPIPE, SIG_IGN); pqsignal(SIGUSR1, procsignal_sigusr1_handler); diff --git a/src/backend/postmaster/walwriter.c b/src/backend/postmaster/walwriter.c index 358c0916ac..a52832fe90 100644 --- a/src/backend/postmaster/walwriter.c +++ b/src/backend/postmaster/walwriter.c @@ -101,7 +101,7 @@ WalWriterMain(void) pqsignal(SIGHUP, SignalHandlerForConfigReload); pqsignal(SIGINT, SignalHandlerForShutdownRequest); pqsignal(SIGTERM, SignalHandlerForShutdownRequest); - pqsignal(SIGQUIT, SignalHandlerForCrashExit); + /* SIGQUIT handler was already set up by InitPostmasterChild */ pqsignal(SIGALRM, SIG_IGN); pqsignal(SIGPIPE, SIG_IGN); pqsignal(SIGUSR1, procsignal_sigusr1_handler); @@ -112,10 +112,6 @@ WalWriterMain(void) */ pqsignal(SIGCHLD, SIG_DFL); - /* We allow SIGQUIT (SignalHandlerForCrashExit) at all times */ - sigdelset(&BlockSig, SIGQUIT); - PG_SETMASK(&BlockSig); - /* * Create a memory context that we will do all our work in. We do this so * that we can reset the context during error recovery and thereby avoid diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c index b180598507..17f1a49f87 100644 --- a/src/backend/replication/walreceiver.c +++ b/src/backend/replication/walreceiver.c @@ -270,7 +270,7 @@ WalReceiverMain(void) pqsignal(SIGHUP, WalRcvSigHupHandler); /* set flag to read config file */ pqsignal(SIGINT, SIG_IGN); pqsignal(SIGTERM, WalRcvShutdownHandler); /* request shutdown */ - pqsignal(SIGQUIT, SignalHandlerForCrashExit); + /* SIGQUIT handler was already set up by InitPostmasterChild */ pqsignal(SIGALRM, SIG_IGN); pqsignal(SIGPIPE, SIG_IGN); pqsignal(SIGUSR1, procsignal_sigusr1_handler); @@ -279,10 +279,6 @@ WalReceiverMain(void) /* Reset some signals that are accepted by postmaster but not here */ pqsignal(SIGCHLD, SIG_DFL); - /* We allow SIGQUIT (SignalHandlerForCrashExit) at all times */ - sigdelset(&BlockSig, SIGQUIT); - PG_SETMASK(&BlockSig); - /* Load the libpq-specific functions */ load_file("libpqwalreceiver", false); if (WalReceiverFunctions == NULL) diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c index 67093383e6..4dbffea240 100644 --- a/src/backend/replication/walsender.c +++ b/src/backend/replication/walsender.c @@ -3041,7 +3041,7 @@ WalSndSignals(void) pqsignal(SIGHUP, SignalHandlerForConfigReload); pqsignal(SIGINT, StatementCancelHandler); /* query cancel */ pqsignal(SIGTERM, die); /* request shutdown */ - pqsignal(SIGQUIT, quickdie); /* hard crash time */ + /* SIGQUIT handler was already set up by InitPostmasterChild */ InitializeTimeouts(); /* establishes SIGALRM handler */ pqsignal(SIGPIPE, SIG_IGN); pqsignal(SIGUSR1, procsignal_sigusr1_handler); diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c index c9424f167c..411cfadbff 100644 --- a/src/backend/tcop/postgres.c +++ b/src/backend/tcop/postgres.c @@ -3820,7 +3820,8 @@ PostgresMain(int argc, char *argv[], } /* - * Set up signal handlers and masks. + * Set up signal handlers. (InitPostmasterChild or InitStandaloneProcess + * has already set up BlockSig and made that the active signal mask.) * * Note that postmaster blocked all signals before forking child process, * so there is no race condition whereby we might receive a signal before @@ -3842,6 +3843,9 @@ PostgresMain(int argc, char *argv[], pqsignal(SIGTERM, die); /* cancel current query and exit */ /* + * In a postmaster child backend, replace SignalHandlerForCrashExit + * with quickdie, so we can tell the client we're dying. + * * In a standalone backend, SIGQUIT can be generated from the keyboard * easily, while SIGTERM cannot, so we make both signals do die() * rather than quickdie(). @@ -3871,16 +3875,6 @@ PostgresMain(int argc, char *argv[], * platforms */ } - pqinitmask(); - - if (IsUnderPostmaster) - { - /* We allow SIGQUIT (quickdie) at all times */ - sigdelset(&BlockSig, SIGQUIT); - } - - PG_SETMASK(&BlockSig); /* block everything except SIGQUIT */ - if (!IsUnderPostmaster) { /* diff --git a/src/backend/utils/init/miscinit.c b/src/backend/utils/init/miscinit.c index cf8f9579c3..ed2ab4b5b2 100644 --- a/src/backend/utils/init/miscinit.c +++ b/src/backend/utils/init/miscinit.c @@ -32,10 +32,12 @@ #include "catalog/pg_authid.h" #include "common/file_perm.h" #include "libpq/libpq.h" +#include "libpq/pqsignal.h" #include "mb/pg_wchar.h" #include "miscadmin.h" #include "pgstat.h" #include "postmaster/autovacuum.h" +#include "postmaster/interrupt.h" #include "postmaster/postmaster.h" #include "storage/fd.h" #include "storage/ipc.h" @@ -133,6 +135,23 @@ InitPostmasterChild(void) elog(FATAL, "setsid() failed: %m"); #endif + /* In EXEC_BACKEND case we will not have inherited BlockSig etc values */ +#ifdef EXEC_BACKEND + pqinitmask(); +#endif + + /* + * Every postmaster child process is expected to respond promptly to + * SIGQUIT at all times. Therefore we centrally remove SIGQUIT from + * BlockSig and install a suitable signal handler. (Client-facing + * processes may choose to replace this default choice of handler with + * quickdie().) All other blockable signals remain blocked for now. + */ + pqsignal(SIGQUIT, SignalHandlerForCrashExit); + + sigdelset(&BlockSig, SIGQUIT); + PG_SETMASK(&BlockSig); + /* Request a signal if the postmaster dies, if possible. */ PostmasterDeathSignalInit(); } @@ -155,6 +174,13 @@ InitStandaloneProcess(const char *argv0) InitLatch(MyLatch); InitializeLatchWaitSet(); + /* + * For consistency with InitPostmasterChild, initialize signal mask here. + * But we don't unblock SIGQUIT or provide a default handler for it. + */ + pqinitmask(); + PG_SETMASK(&BlockSig); + /* Compute paths, no postmaster to inherit from */ if (my_exec_path[0] == '\0') {