From 1f0bd35300dd0c669d4bbf1f50857f17ae64b08c Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Mon, 13 Mar 2023 10:45:14 +1300 Subject: [PATCH 3/3] Use nanosleep() to implement pg_usleep(). The previous coding based on select() required a lot of commentary about historical portability concerns. We can just get rid of all that and use the POSIX nanosleep() function. The newer clock_nanosleep() variant might be better, because it can take a CLOCK_MONOTONIC argument to avoid the chance that ntpd adjustments affect sleep times, but macOS hasn't caught up with that yet. --- src/port/pgsleep.c | 24 +++++++++--------------- 1 file changed, 9 insertions(+), 15 deletions(-) diff --git a/src/port/pgsleep.c b/src/port/pgsleep.c index dcba7eda44..3f42021596 100644 --- a/src/port/pgsleep.c +++ b/src/port/pgsleep.c @@ -12,9 +12,7 @@ */ #include "c.h" -#include -#include -#include +#include /* * In a Windows backend, we don't use this implementation, but rather @@ -32,15 +30,11 @@ * * On machines where "long" is 32 bits, the maximum delay is ~2000 seconds. * - * CAUTION: the behavior when a signal arrives during the sleep is platform - * dependent. On most Unix-ish platforms, a signal does not terminate the - * sleep; but on some, it will (the Windows implementation also allows signals - * to terminate pg_usleep). And there are platforms where not only does a - * signal not terminate the sleep, but it actually resets the timeout counter - * so that the sleep effectively starts over! It is therefore rather hazardous - * to use this for long sleeps; a continuing stream of signal events could - * prevent the sleep from ever terminating. Better practice for long sleeps - * is to use WaitLatch() with a timeout. + * CAUTION: if interrupted by a signal, this function will return, but its + * interface doesn't report that. It's not a good idea to use this + * for long sleeps in the backend, because backends are expected to respond to + * interrupts promptly. Better practice for long sleeps is to use WaitLatch() + * with a timeout. */ void pg_usleep(long microsec) @@ -48,11 +42,11 @@ pg_usleep(long microsec) if (microsec > 0) { #ifndef WIN32 - struct timeval delay; + struct timespec delay; delay.tv_sec = microsec / 1000000L; - delay.tv_usec = microsec % 1000000L; - (void) select(0, NULL, NULL, NULL, &delay); + delay.tv_nsec = (microsec % 1000000L) * 1000; + (void) nanosleep(&delay, NULL); #else SleepEx((microsec < 500 ? 1 : (microsec + 500) / 1000), FALSE); #endif -- 2.39.2