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Commit6492560

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Revert "Use pselect(2) not select(2), if available, to wait in postmaster's loop."
This reverts commit81069a9.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 parent81069a9 commit6492560

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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
@@ -12892,7 +12892,7 @@ fi
1289212892
LIBS_including_readline="$LIBS"
1289312893
LIBS=`echo"$LIBS"| sed -e's/-ledit//g' -e's/-lreadline//g'`
1289412894

12895-
forac_funcin cbrt clock_gettime 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
12895+
forac_funcin cbrt clock_gettime 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
1289612896
do:
1289712897
as_ac_var=`$as_echo"ac_cv_func_$ac_func"|$as_tr_sh`
1289812898
ac_fn_c_check_func"$LINENO""$ac_func""$as_ac_var"

‎configure.in

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1429,7 +1429,7 @@ PGAC_FUNC_WCSTOMBS_L
14291429
LIBS_including_readline="$LIBS"
14301430
LIBS=`echo "$LIBS" | sed -e 's/-ledit//g' -e 's/-lreadline//g'`
14311431

1432-
AC_CHECK_FUNCS([cbrt clock_gettime 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])
1432+
AC_CHECK_FUNCS([cbrt clock_gettime 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])
14331433

14341434
AC_REPLACE_FUNCS(fseeko)
14351435
case $host_os in

‎src/backend/postmaster/postmaster.c

Lines changed: 17 additions & 46 deletions
Original file line numberDiff line numberDiff line change
@@ -614,9 +614,9 @@ PostmasterMain(int argc, char *argv[])
614614
* In the postmaster, we want to install non-ignored handlers *without*
615615
* SA_RESTART. This is because they'll be blocked at all times except
616616
* when ServerLoop is waiting for something to happen, and during that
617-
* window, we want signals to exit thepselect(2) wait so that ServerLoop
617+
* window, we want signals to exit theselect(2) wait so that ServerLoop
618618
* can respond if anything interesting happened. On some platforms,
619-
* signals marked SA_RESTART would not cause thepselect() wait to end.
619+
* signals marked SA_RESTART would not cause theselect() wait to end.
620620
* Child processes will generally want SA_RESTART, but we expect them to
621621
* set up their own handlers before unblocking signals.
622622
*
@@ -1670,8 +1670,6 @@ ServerLoop(void)
16701670
for (;;)
16711671
{
16721672
fd_setrmask;
1673-
fd_set*rmask_p;
1674-
structtimevaltimeout;
16751673
intselres;
16761674
time_tnow;
16771675

@@ -1681,64 +1679,37 @@ ServerLoop(void)
16811679
* We block all signals except while sleeping. That makes it safe for
16821680
* signal handlers, which again block all signals while executing, to
16831681
* do nontrivial work.
1682+
*
1683+
* If we are in PM_WAIT_DEAD_END state, then we don't want to accept
1684+
* any new connections, so we don't call select(), and just sleep.
16841685
*/
1686+
memcpy((char*)&rmask, (char*)&readmask,sizeof(fd_set));
1687+
16851688
if (pmState==PM_WAIT_DEAD_END)
16861689
{
1687-
/*
1688-
* If we are in PM_WAIT_DEAD_END state, then we don't want to
1689-
* accept any new connections, so pass a null rmask.
1690-
*/
1691-
rmask_p=NULL;
1692-
timeout.tv_sec=0;
1693-
timeout.tv_usec=100000;/* 100 msec seems reasonable */
1690+
PG_SETMASK(&UnBlockSig);
1691+
1692+
pg_usleep(100000L);/* 100 msec seems reasonable */
1693+
selres=0;
1694+
1695+
PG_SETMASK(&BlockSig);
16941696
}
16951697
else
16961698
{
1697-
/* Normal case: check sockets, and compute a suitable timeout */
1698-
memcpy(&rmask,&readmask,sizeof(fd_set));
1699-
rmask_p=&rmask;
1699+
/* must set timeout each time; some OSes change it! */
1700+
structtimevaltimeout;
17001701

17011702
/* Needs to run with blocked signals! */
17021703
DetermineSleepTime(&timeout);
1703-
}
17041704

1705-
/*
1706-
* We prefer to wait with pselect(2) if available, as using that,
1707-
* together with *not* using SA_RESTART for signals, guarantees that
1708-
* we will get kicked off the wait if a signal occurs.
1709-
*
1710-
* If we lack pselect(2), fake it with select(2). This has a race
1711-
* condition: a signal that was already pending will be delivered
1712-
* before we reach the select(), and therefore the select() will wait,
1713-
* even though we might wish to do something in response. Therefore,
1714-
* beware of putting any time-critical signal response logic into
1715-
* ServerLoop rather than into the signal handler itself. It will run
1716-
* eventually, but maybe not till after a timeout delay.
1717-
*
1718-
* Some implementations of pselect() are reportedly not atomic, making
1719-
* the first alternative here functionally equivalent to the second.
1720-
* Not much we can do about that though.
1721-
*/
1722-
{
1723-
#ifdefHAVE_PSELECT
1724-
/* pselect uses a randomly different timeout API, sigh */
1725-
structtimespecptimeout;
1726-
1727-
ptimeout.tv_sec=timeout.tv_sec;
1728-
ptimeout.tv_nsec=timeout.tv_usec*1000;
1729-
1730-
selres=pselect(nSockets,rmask_p,NULL,NULL,
1731-
&ptimeout,&UnBlockSig);
1732-
#else
17331705
PG_SETMASK(&UnBlockSig);
17341706

1735-
selres=select(nSockets,rmask_p,NULL,NULL,&timeout);
1707+
selres=select(nSockets,&rmask,NULL,NULL,&timeout);
17361708

17371709
PG_SETMASK(&BlockSig);
1738-
#endif
17391710
}
17401711

1741-
/* Now check the select()/pselect() result */
1712+
/* Now check the select() result */
17421713
if (selres<0)
17431714
{
17441715
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
@@ -400,9 +400,6 @@
400400
/* Define to 1 if the assembler supports PPC's LWARX mutex hint bit. */
401401
#undef HAVE_PPC_LWARX_MUTEX_HINT
402402

403-
/* Define to 1 if you have the `pselect' function. */
404-
#undef HAVE_PSELECT
405-
406403
/* Define to 1 if you have the `pstat' function. */
407404
#undef HAVE_PSTAT
408405

‎src/include/pg_config.h.win32

Lines changed: 0 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -267,9 +267,6 @@
267267
/* Define to 1 if you have the <poll.h> header file. */
268268
/* #undef HAVE_POLL_H */
269269

270-
/* Define to 1 if you have the `pselect' function. */
271-
/* #undef HAVE_PSELECT */
272-
273270
/* Define to 1 if you have the `pstat' function. */
274271
/* #undef HAVE_PSTAT */
275272

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