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Commite615605

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Revert "Use pselect(2) not select(2), if available, to wait in postmaster's loop."
This reverts commitb9515b6.Buildfarm results suggest that some platforms have versions of pselect(2)that are not merely non-atomic, but flat out non-functional. Revert theuse-pselect patch to confirm this diagnosis (and exclude the no-SA_RESTARTpatch as the source of trouble). If it's so, we should probably look intoblacklisting specific platforms that have broken pselect.Discussion:https://postgr.es/m/9696.1493072081@sss.pgh.pa.us
1 parentb9515b6 commite615605

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5 files changed

+19
-54
lines changed

5 files changed

+19
-54
lines changed

‎configure

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -12504,7 +12504,7 @@ fi
1250412504
LIBS_including_readline="$LIBS"
1250512505
LIBS=`echo"$LIBS"| sed -e's/-ledit//g' -e's/-lreadline//g'`
1250612506

12507-
forac_funcin cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove pollpselectpstat pthread_is_threaded_np readlink setproctitle setsid shm_open symlink sync_file_range towlower utime utimes wcstombs wcstombs_l
12507+
forac_funcin cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove poll pstat pthread_is_threaded_np readlink setproctitle setsid shm_open symlink sync_file_range towlower utime utimes wcstombs wcstombs_l
1250812508
do:
1250912509
as_ac_var=`$as_echo"ac_cv_func_$ac_func"|$as_tr_sh`
1251012510
ac_fn_c_check_func"$LINENO""$ac_func""$as_ac_var"

‎configure.in

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1456,7 +1456,7 @@ PGAC_FUNC_WCSTOMBS_L
14561456
LIBS_including_readline="$LIBS"
14571457
LIBS=`echo "$LIBS" | sed -e 's/-ledit//g' -e 's/-lreadline//g'`
14581458

1459-
AC_CHECK_FUNCS([cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove pollpselectpstat pthread_is_threaded_np readlink setproctitle setsid shm_open symlink sync_file_range towlower utime utimes wcstombs wcstombs_l])
1459+
AC_CHECK_FUNCS([cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit mbstowcs_l memmove poll pstat pthread_is_threaded_np readlink setproctitle setsid shm_open symlink sync_file_range towlower utime utimes wcstombs wcstombs_l])
14601460

14611461
AC_REPLACE_FUNCS(fseeko)
14621462
case $host_os in

‎src/backend/postmaster/postmaster.c

Lines changed: 17 additions & 46 deletions
Original file line numberDiff line numberDiff line change
@@ -606,9 +606,9 @@ PostmasterMain(int argc, char *argv[])
606606
* In the postmaster, we want to install non-ignored handlers *without*
607607
* SA_RESTART. This is because they'll be blocked at all times except
608608
* when ServerLoop is waiting for something to happen, and during that
609-
* window, we want signals to exit thepselect(2) wait so that ServerLoop
609+
* window, we want signals to exit theselect(2) wait so that ServerLoop
610610
* can respond if anything interesting happened. On some platforms,
611-
* signals marked SA_RESTART would not cause thepselect() wait to end.
611+
* signals marked SA_RESTART would not cause theselect() wait to end.
612612
* Child processes will generally want SA_RESTART, but we expect them to
613613
* set up their own handlers before unblocking signals.
614614
*
@@ -1642,8 +1642,6 @@ ServerLoop(void)
16421642
for (;;)
16431643
{
16441644
fd_setrmask;
1645-
fd_set*rmask_p;
1646-
structtimevaltimeout;
16471645
intselres;
16481646
time_tnow;
16491647

@@ -1653,64 +1651,37 @@ ServerLoop(void)
16531651
* We block all signals except while sleeping. That makes it safe for
16541652
* signal handlers, which again block all signals while executing, to
16551653
* do nontrivial work.
1654+
*
1655+
* If we are in PM_WAIT_DEAD_END state, then we don't want to accept
1656+
* any new connections, so we don't call select(), and just sleep.
16561657
*/
1658+
memcpy((char*)&rmask, (char*)&readmask,sizeof(fd_set));
1659+
16571660
if (pmState==PM_WAIT_DEAD_END)
16581661
{
1659-
/*
1660-
* If we are in PM_WAIT_DEAD_END state, then we don't want to
1661-
* accept any new connections, so pass a null rmask.
1662-
*/
1663-
rmask_p=NULL;
1664-
timeout.tv_sec=0;
1665-
timeout.tv_usec=100000;/* 100 msec seems reasonable */
1662+
PG_SETMASK(&UnBlockSig);
1663+
1664+
pg_usleep(100000L);/* 100 msec seems reasonable */
1665+
selres=0;
1666+
1667+
PG_SETMASK(&BlockSig);
16661668
}
16671669
else
16681670
{
1669-
/* Normal case: check sockets, and compute a suitable timeout */
1670-
memcpy(&rmask,&readmask,sizeof(fd_set));
1671-
rmask_p=&rmask;
1671+
/* must set timeout each time; some OSes change it! */
1672+
structtimevaltimeout;
16721673

16731674
/* Needs to run with blocked signals! */
16741675
DetermineSleepTime(&timeout);
1675-
}
16761676

1677-
/*
1678-
* We prefer to wait with pselect(2) if available, as using that,
1679-
* together with *not* using SA_RESTART for signals, guarantees that
1680-
* we will get kicked off the wait if a signal occurs.
1681-
*
1682-
* If we lack pselect(2), fake it with select(2). This has a race
1683-
* condition: a signal that was already pending will be delivered
1684-
* before we reach the select(), and therefore the select() will wait,
1685-
* even though we might wish to do something in response. Therefore,
1686-
* beware of putting any time-critical signal response logic into
1687-
* ServerLoop rather than into the signal handler itself. It will run
1688-
* eventually, but maybe not till after a timeout delay.
1689-
*
1690-
* Some implementations of pselect() are reportedly not atomic, making
1691-
* the first alternative here functionally equivalent to the second.
1692-
* Not much we can do about that though.
1693-
*/
1694-
{
1695-
#ifdefHAVE_PSELECT
1696-
/* pselect uses a randomly different timeout API, sigh */
1697-
structtimespecptimeout;
1698-
1699-
ptimeout.tv_sec=timeout.tv_sec;
1700-
ptimeout.tv_nsec=timeout.tv_usec*1000;
1701-
1702-
selres=pselect(nSockets,rmask_p,NULL,NULL,
1703-
&ptimeout,&UnBlockSig);
1704-
#else
17051677
PG_SETMASK(&UnBlockSig);
17061678

1707-
selres=select(nSockets,rmask_p,NULL,NULL,&timeout);
1679+
selres=select(nSockets,&rmask,NULL,NULL,&timeout);
17081680

17091681
PG_SETMASK(&BlockSig);
1710-
#endif
17111682
}
17121683

1713-
/* Now check the select()/pselect() result */
1684+
/* Now check the select() result */
17141685
if (selres<0)
17151686
{
17161687
if (errno!=EINTR&&errno!=EWOULDBLOCK)

‎src/include/pg_config.h.in

Lines changed: 0 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -397,9 +397,6 @@
397397
/* Define to 1 if the assembler supports PPC's LWARX mutex hint bit. */
398398
#undef HAVE_PPC_LWARX_MUTEX_HINT
399399

400-
/* Define to 1 if you have the `pselect' function. */
401-
#undef HAVE_PSELECT
402-
403400
/* Define to 1 if you have the `pstat' function. */
404401
#undef HAVE_PSTAT
405402

‎src/include/pg_config.h.win32

Lines changed: 0 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -264,9 +264,6 @@
264264
/* Define to 1 if you have the <poll.h> header file. */
265265
/* #undef HAVE_POLL_H */
266266

267-
/* Define to 1 if you have the `pselect' function. */
268-
/* #undef HAVE_PSELECT */
269-
270267
/* Define to 1 if you have the `pstat' function. */
271268
/* #undef HAVE_PSTAT */
272269

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