From 9a2dd1ed57c3364c98fe459071e84702015c5814 Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Sat, 14 May 2022 10:15:30 +1200 Subject: [PATCH v3] Don't trust signalfd() on illumos. Hangs and kernel panics have been reported on illumos systems since we started using signalfd() to receive latch wakeup events. A bug report exists at https://www.illumos.org/issues/13700 but no fix is available yet. Provide a way to go back to using a self-pipe with -DWAIT_USE_SELF_PIPE, and make that the default on that platform. Users can explicitly provide -DWAIT_USE_SIGNALFD if required in case that's helpful to investigate what's going wrong. Back-patch to 14, where we started using signalfd(). Reported-by: Japin Li Reported-by: Olaf Bohlen (off-list) Reviewed-by: Japin Li Discussion: https://postgr.es/m/MEYP282MB1669C8D88F0997354C2313C1B6CA9%40MEYP282MB1669.AUSP282.PROD.OUTLOOK.COM --- src/backend/storage/ipc/latch.c | 58 +++++++++++++++++++++++---------- 1 file changed, 40 insertions(+), 18 deletions(-) diff --git a/src/backend/storage/ipc/latch.c b/src/backend/storage/ipc/latch.c index 78c6a89271..fba8a9ea94 100644 --- a/src/backend/storage/ipc/latch.c +++ b/src/backend/storage/ipc/latch.c @@ -72,7 +72,7 @@ #if defined(WAIT_USE_EPOLL) || defined(WAIT_USE_POLL) || \ defined(WAIT_USE_KQUEUE) || defined(WAIT_USE_WIN32) /* don't overwrite manual choice */ -#elif defined(HAVE_SYS_EPOLL_H) && defined(HAVE_SYS_SIGNALFD_H) +#elif defined(HAVE_SYS_EPOLL_H) #define WAIT_USE_EPOLL #elif defined(HAVE_KQUEUE) #define WAIT_USE_KQUEUE @@ -84,6 +84,22 @@ #error "no wait set implementation available" #endif +/* + * By default, we use a self-pipe with poll() and a signalfd with epoll(), if + * available. We avoid signalfd on illumos for now based on problem reports. + * For testing the choice can also be manually specified. + */ +#if defined(WAIT_USE_POLL) || defined(WAIT_USE_EPOLL) +#if defined(WAIT_USE_SELF_PIPE) || defined(WAIT_USE_SIGNALFD) +/* don't overwrite manual choice */ +#elif defined(WAIT_USE_EPOLL) && defined(HAVE_SYS_SIGNALFD_H) && \ + !defined(__illumos__) +#define WAIT_USE_SIGNALFD +#else +#define WAIT_USE_SELF_PIPE +#endif +#endif + /* typedef in latch.h */ struct WaitEventSet { @@ -146,12 +162,12 @@ static WaitEventSet *LatchWaitSet; static volatile sig_atomic_t waiting = false; #endif -#ifdef WAIT_USE_EPOLL +#ifdef WAIT_USE_SIGNALFD /* On Linux, we'll receive SIGURG via a signalfd file descriptor. */ static int signal_fd = -1; #endif -#if defined(WAIT_USE_POLL) +#ifdef WAIT_USE_SELF_PIPE /* Read and write ends of the self-pipe */ static int selfpipe_readfd = -1; static int selfpipe_writefd = -1; @@ -164,7 +180,7 @@ static void latch_sigurg_handler(SIGNAL_ARGS); static void sendSelfPipeByte(void); #endif -#if defined(WAIT_USE_POLL) || defined(WAIT_USE_EPOLL) +#if defined(WAIT_USE_SELF_PIPE) || defined(WAIT_USE_SIGNALFD) static void drain(void); #endif @@ -190,7 +206,7 @@ static inline int WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout, void InitializeLatchSupport(void) { -#if defined(WAIT_USE_POLL) +#if defined(WAIT_USE_SELF_PIPE) int pipefd[2]; if (IsUnderPostmaster) @@ -264,7 +280,7 @@ InitializeLatchSupport(void) pqsignal(SIGURG, latch_sigurg_handler); #endif -#ifdef WAIT_USE_EPOLL +#ifdef WAIT_USE_SIGNALFD sigset_t signalfd_mask; /* Block SIGURG, because we'll receive it through a signalfd. */ @@ -316,7 +332,7 @@ ShutdownLatchSupport(void) LatchWaitSet = NULL; } -#if defined(WAIT_USE_POLL) +#if defined(WAIT_USE_SELF_PIPE) close(selfpipe_readfd); close(selfpipe_writefd); selfpipe_readfd = -1; @@ -324,7 +340,7 @@ ShutdownLatchSupport(void) selfpipe_owner_pid = InvalidPid; #endif -#if defined(WAIT_USE_EPOLL) +#if defined(WAIT_USE_SIGNALFD) close(signal_fd); signal_fd = -1; #endif @@ -341,9 +357,12 @@ InitLatch(Latch *latch) latch->owner_pid = MyProcPid; latch->is_shared = false; -#if defined(WAIT_USE_POLL) +#if defined(WAIT_USE_SELF_PIPE) /* Assert InitializeLatchSupport has been called in this process */ Assert(selfpipe_readfd >= 0 && selfpipe_owner_pid == MyProcPid); +#elif defined(WAIT_USE_SIGNALFD) + /* Assert InitializeLatchSupport has been called in this process */ + Assert(signal_fd >= 0); #elif defined(WAIT_USE_WIN32) latch->event = CreateEvent(NULL, TRUE, FALSE, NULL); if (latch->event == NULL) @@ -405,9 +424,12 @@ OwnLatch(Latch *latch) /* Sanity checks */ Assert(latch->is_shared); -#if defined(WAIT_USE_POLL) +#if defined(WAIT_USE_SELF_PIPE) /* Assert InitializeLatchSupport has been called in this process */ Assert(selfpipe_readfd >= 0 && selfpipe_owner_pid == MyProcPid); +#elif defined(WAIT_USE_SIGNALFD) + /* Assert InitializeLatchSupport has been called in this process */ + Assert(signal_fd >= 0); #endif if (latch->owner_pid != 0) @@ -617,7 +639,7 @@ SetLatch(Latch *latch) return; else if (owner_pid == MyProcPid) { -#if defined(WAIT_USE_POLL) +#if defined(WAIT_USE_SELF_PIPE) if (waiting) sendSelfPipeByte(); #else @@ -904,9 +926,9 @@ AddWaitEventToSet(WaitEventSet *set, uint32 events, pgsocket fd, Latch *latch, { set->latch = latch; set->latch_pos = event->pos; -#if defined(WAIT_USE_POLL) +#if defined(WAIT_USE_SELF_PIPE) event->fd = selfpipe_readfd; -#elif defined(WAIT_USE_EPOLL) +#elif defined(WAIT_USE_SIGNALFD) event->fd = signal_fd; #else event->fd = PGINVALID_SOCKET; @@ -2083,7 +2105,7 @@ GetNumRegisteredWaitEvents(WaitEventSet *set) return set->nevents; } -#if defined(WAIT_USE_POLL) +#if defined(WAIT_USE_SELF_PIPE) /* * SetLatch uses SIGURG to wake up the process waiting on the latch. @@ -2134,7 +2156,7 @@ retry: #endif -#if defined(WAIT_USE_POLL) || defined(WAIT_USE_EPOLL) +#if defined(WAIT_USE_SELF_PIPE) || defined(WAIT_USE_SIGNALFD) /* * Read all available data from self-pipe or signalfd. @@ -2150,7 +2172,7 @@ drain(void) int rc; int fd; -#ifdef WAIT_USE_POLL +#ifdef WAIT_USE_SELF_PIPE fd = selfpipe_readfd; #else fd = signal_fd; @@ -2168,7 +2190,7 @@ drain(void) else { waiting = false; -#ifdef WAIT_USE_POLL +#ifdef WAIT_USE_SELF_PIPE elog(ERROR, "read() on self-pipe failed: %m"); #else elog(ERROR, "read() on signalfd failed: %m"); @@ -2178,7 +2200,7 @@ drain(void) else if (rc == 0) { waiting = false; -#ifdef WAIT_USE_POLL +#ifdef WAIT_USE_SELF_PIPE elog(ERROR, "unexpected EOF on self-pipe"); #else elog(ERROR, "unexpected EOF on signalfd"); -- 2.36.0