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Commita64ca63

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Use WaitLatch, not pg_usleep, for delaying in pg_sleep().
This avoids platform-dependent behavior wherein pg_sleep() might fail to beinterrupted by statement timeout, query cancel, SIGTERM, etc. Also, sincethere's no reason to wake up once a second any more, we can reduce thepower consumption of a sleeping backend a tad.Back-patch to 9.3, since use of SA_RESTART for SIGALRM makes this a biggerissue than it used to be.
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‎src/backend/utils/adt/misc.c

Lines changed: 17 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -384,16 +384,16 @@ pg_sleep(PG_FUNCTION_ARGS)
384384
float8endtime;
385385

386386
/*
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* Webreak the requested sleep into segments of no more than 1 second, to
388-
*put an upper bound on how long it will take us to respond to a cancel
389-
*or die interrupt. (Note that pg_usleepisinterruptible by signals on
390-
*some platforms but not others.)Also, this method avoids exposing
391-
*pg_usleep's upper bound on allowed delays.
387+
* Wesleep using WaitLatch, to ensure that we'll wake up promptly if an
388+
*important signal (such as SIGALRM or SIGINT) arrives. Because
389+
*WaitLatch's upper limit of delayisINT_MAX milliseconds, and the user
390+
*might ask for more than that, we sleep for at most 10 minutes and then
391+
*loop.
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*
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* By computing the intended stop time initially, we avoid accumulation of
394394
* extra delay across multiple sleeps.This also ensures we won't delay
395-
* less than the specified timeif pg_usleep isinterruptedbyother
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*signals such as SIGHUP.
395+
* less than the specified timewhen WaitLatch isterminated earlybya
396+
*non-query-cancelling signal such as SIGHUP.
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*/
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399399
#ifdefHAVE_INT64_TIMESTAMP
@@ -407,15 +407,22 @@ pg_sleep(PG_FUNCTION_ARGS)
407407
for (;;)
408408
{
409409
float8delay;
410+
longdelay_ms;
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411412
CHECK_FOR_INTERRUPTS();
413+
412414
delay=endtime-GetNowFloat();
413-
if (delay >=1.0)
414-
pg_usleep(1000000L);
415+
if (delay >=600.0)
416+
delay_ms=600000;
415417
elseif (delay>0.0)
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pg_usleep((long)ceil(delay*1000000.0));
418+
delay_ms= (long)ceil(delay*1000.0);
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else
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break;
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422+
(void)WaitLatch(&MyProc->procLatch,
423+
WL_LATCH_SET |WL_TIMEOUT,
424+
delay_ms);
425+
ResetLatch(&MyProc->procLatch);
419426
}
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421428
PG_RETURN_VOID();

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