diff options
| -rw-r--r-- | src/backend/port/unix_latch.c | 50 |
1 files changed, 34 insertions, 16 deletions
diff --git a/src/backend/port/unix_latch.c b/src/backend/port/unix_latch.c index 9f8b8d54f07..e7be7ec1179 100644 --- a/src/backend/port/unix_latch.c +++ b/src/backend/port/unix_latch.c @@ -56,6 +56,22 @@ #include "storage/pmsignal.h" #include "storage/shmem.h" +/* + * Select the fd readiness primitive to use. Normally the "most modern" + * primitive supported by the OS will be used, but for testing it can be + * useful to manually specify the used primitive. If desired, just add a + * define somewhere before this block. + */ +#if defined(LATCH_USE_POLL) || defined(LATCH_USE_SELECT) +/* don't overwrite manual choice */ +#elif defined(HAVE_POLL) +#define LATCH_USE_POLL +#elif HAVE_SYS_SELECT_H +#define LATCH_USE_SELECT +#else +#error "no latch implementation available" +#endif + /* Are we currently in WaitLatch? The signal handler would like to know. */ static volatile sig_atomic_t waiting = false; @@ -215,10 +231,10 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock, cur_time; long cur_timeout; -#ifdef HAVE_POLL +#if defined(LATCH_USE_POLL) struct pollfd pfds[3]; int nfds; -#else +#elif defined(LATCH_USE_SELECT) struct timeval tv, *tvp; fd_set input_mask; @@ -248,7 +264,7 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock, Assert(timeout >= 0 && timeout <= INT_MAX); cur_timeout = timeout; -#ifndef HAVE_POLL +#ifdef LATCH_USE_SELECT tv.tv_sec = cur_timeout / 1000L; tv.tv_usec = (cur_timeout % 1000L) * 1000L; tvp = &tv; @@ -258,7 +274,7 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock, { cur_timeout = -1; -#ifndef HAVE_POLL +#ifdef LATCH_USE_SELECT tvp = NULL; #endif } @@ -292,16 +308,10 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock, } /* - * Must wait ... we use poll(2) if available, otherwise select(2). - * - * On at least older linux kernels select(), in violation of POSIX, - * doesn't reliably return a socket as writable if closed - but we - * rely on that. So far all the known cases of this problem are on - * platforms that also provide a poll() implementation without that - * bug. If we find one where that's not the case, we'll need to add a - * workaround. + * Must wait ... we use the polling interface determined at the top of + * this file to do so. */ -#ifdef HAVE_POLL +#if defined(LATCH_USE_POLL) nfds = 0; if (wakeEvents & (WL_SOCKET_READABLE | WL_SOCKET_WRITEABLE)) { @@ -397,8 +407,16 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock, result |= WL_POSTMASTER_DEATH; } } -#else /* !HAVE_POLL */ +#elif defined(LATCH_USE_SELECT) + /* + * On at least older linux kernels select(), in violation of POSIX, + * doesn't reliably return a socket as writable if closed - but we + * rely on that. So far all the known cases of this problem are on + * platforms that also provide a poll() implementation without that + * bug. If we find one where that's not the case, we'll need to add a + * workaround. + */ FD_ZERO(&input_mask); FD_ZERO(&output_mask); @@ -478,7 +496,7 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock, result |= WL_POSTMASTER_DEATH; } } -#endif /* HAVE_POLL */ +#endif /* LATCH_USE_SELECT */ /* If we're not done, update cur_timeout for next iteration */ if (result == 0 && (wakeEvents & WL_TIMEOUT)) @@ -491,7 +509,7 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock, /* Timeout has expired, no need to continue looping */ result |= WL_TIMEOUT; } -#ifndef HAVE_POLL +#ifdef LATCH_USE_SELECT else { tv.tv_sec = cur_timeout / 1000L; |