Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commit9abb2bf

Browse files
committed
In the postmaster, rely on the signal infrastructure to block signals.
POSIX sigaction(2) can be told to block a set of signals while asignal handler executes. Make use of that instead of manuallyblocking and unblocking signals in the postmaster's signal handlers.This should save a few cycles, and it also prevents recursiveinvocation of signal handlers when many signals arrive in closesuccession. We have seen buildfarm failures that seem to be due topostmaster stack overflow caused by such recursion (exacerbated bya Linux PPC64 kernel bug).This doesn't change anything about the way that it works on Windows.Somebody might consider adjusting port/win32/signal.c to let it worksimilarly, but I'm not in a position to do that.For the moment, just apply to HEAD. Possibly we should considerback-patching this, but it'd be good to let it age awhile first.Discussion:https://postgr.es/m/14878.1570820201@sss.pgh.pa.us
1 parentf38291e commit9abb2bf

File tree

5 files changed

+116
-57
lines changed

5 files changed

+116
-57
lines changed

‎src/backend/libpq/pqsignal.c

Lines changed: 49 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -95,3 +95,52 @@ pqinitmask(void)
9595
sigdelset(&StartupBlockSig,SIGALRM);
9696
#endif
9797
}
98+
99+
/*
100+
* Set up a postmaster signal handler for signal "signo"
101+
*
102+
* Returns the previous handler.
103+
*
104+
* This is used only in the postmaster, which has its own odd approach to
105+
* signal handling. For signals with handlers, we block all signals for the
106+
* duration of signal handler execution. We also do not set the SA_RESTART
107+
* flag; this should be safe given the tiny range of code in which the
108+
* postmaster ever unblocks signals.
109+
*
110+
* pqinitmask() must have been invoked previously.
111+
*
112+
* On Windows, this function is just an alias for pqsignal()
113+
* (and note that it's calling the code in src/backend/port/win32/signal.c,
114+
* not src/port/pqsignal.c). On that platform, the postmaster's signal
115+
* handlers still have to block signals for themselves.
116+
*/
117+
pqsigfunc
118+
pqsignal_pm(intsigno,pqsigfuncfunc)
119+
{
120+
#ifndefWIN32
121+
structsigactionact,
122+
oact;
123+
124+
act.sa_handler=func;
125+
if (func==SIG_IGN||func==SIG_DFL)
126+
{
127+
/* in these cases, act the same as pqsignal() */
128+
sigemptyset(&act.sa_mask);
129+
act.sa_flags=SA_RESTART;
130+
}
131+
else
132+
{
133+
act.sa_mask=BlockSig;
134+
act.sa_flags=0;
135+
}
136+
#ifdefSA_NOCLDSTOP
137+
if (signo==SIGCHLD)
138+
act.sa_flags |=SA_NOCLDSTOP;
139+
#endif
140+
if (sigaction(signo,&act,&oact)<0)
141+
returnSIG_ERR;
142+
returnoact.sa_handler;
143+
#else/* WIN32 */
144+
returnpqsignal(signo,func);
145+
#endif
146+
}

‎src/backend/postmaster/postmaster.c

Lines changed: 64 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -606,14 +606,25 @@ PostmasterMain(int argc, char *argv[])
606606
/*
607607
* Set up signal handlers for the postmaster process.
608608
*
609-
* In the postmaster, we want to install non-ignored handlers *without*
610-
* SA_RESTART. This is because they'll be blocked at all times except
611-
* when ServerLoop is waiting for something to happen, and during that
612-
* window, we want signals to exit the select(2) wait so that ServerLoop
613-
* can respond if anything interesting happened. On some platforms,
614-
* signals marked SA_RESTART would not cause the select() wait to end.
615-
* Child processes will generally want SA_RESTART, but we expect them to
616-
* set up their own handlers before unblocking signals.
609+
* In the postmaster, we use pqsignal_pm() rather than pqsignal() (which
610+
* is used by all child processes and client processes). That has a
611+
* couple of special behaviors:
612+
*
613+
* 1. Except on Windows, we tell sigaction() to block all signals for the
614+
* duration of the signal handler. This is faster than our old approach
615+
* of blocking/unblocking explicitly in the signal handler, and it should
616+
* also prevent excessive stack consumption if signals arrive quickly.
617+
*
618+
* 2. We do not set the SA_RESTART flag. This is because signals will be
619+
* blocked at all times except when ServerLoop is waiting for something to
620+
* happen, and during that window, we want signals to exit the select(2)
621+
* wait so that ServerLoop can respond if anything interesting happened.
622+
* On some platforms, signals marked SA_RESTART would not cause the
623+
* select() wait to end.
624+
*
625+
* Child processes will generally want SA_RESTART, so pqsignal() sets that
626+
* flag. We expect children to set up their own handlers before
627+
* unblocking signals.
617628
*
618629
* CAUTION: when changing this list, check for side-effects on the signal
619630
* handling setup of child processes. See tcop/postgres.c,
@@ -625,18 +636,16 @@ PostmasterMain(int argc, char *argv[])
625636
pqinitmask();
626637
PG_SETMASK(&BlockSig);
627638

628-
pqsignal_no_restart(SIGHUP,SIGHUP_handler);/* reread config file and
629-
* have children do same */
630-
pqsignal_no_restart(SIGINT,pmdie);/* send SIGTERM and shut down */
631-
pqsignal_no_restart(SIGQUIT,pmdie);/* send SIGQUIT and die */
632-
pqsignal_no_restart(SIGTERM,pmdie);/* wait for children and shut down */
633-
pqsignal(SIGALRM,SIG_IGN);/* ignored */
634-
pqsignal(SIGPIPE,SIG_IGN);/* ignored */
635-
pqsignal_no_restart(SIGUSR1,sigusr1_handler);/* message from child
636-
* process */
637-
pqsignal_no_restart(SIGUSR2,dummy_handler);/* unused, reserve for
638-
* children */
639-
pqsignal_no_restart(SIGCHLD,reaper);/* handle child termination */
639+
pqsignal_pm(SIGHUP,SIGHUP_handler);/* reread config file and have
640+
* children do same */
641+
pqsignal_pm(SIGINT,pmdie);/* send SIGTERM and shut down */
642+
pqsignal_pm(SIGQUIT,pmdie);/* send SIGQUIT and die */
643+
pqsignal_pm(SIGTERM,pmdie);/* wait for children and shut down */
644+
pqsignal_pm(SIGALRM,SIG_IGN);/* ignored */
645+
pqsignal_pm(SIGPIPE,SIG_IGN);/* ignored */
646+
pqsignal_pm(SIGUSR1,sigusr1_handler);/* message from child process */
647+
pqsignal_pm(SIGUSR2,dummy_handler);/* unused, reserve for children */
648+
pqsignal_pm(SIGCHLD,reaper);/* handle child termination */
640649

641650
/*
642651
* No other place in Postgres should touch SIGTTIN/SIGTTOU handling. We
@@ -646,15 +655,15 @@ PostmasterMain(int argc, char *argv[])
646655
* child processes should just allow the inherited settings to stand.
647656
*/
648657
#ifdefSIGTTIN
649-
pqsignal(SIGTTIN,SIG_IGN);/* ignored */
658+
pqsignal_pm(SIGTTIN,SIG_IGN);/* ignored */
650659
#endif
651660
#ifdefSIGTTOU
652-
pqsignal(SIGTTOU,SIG_IGN);/* ignored */
661+
pqsignal_pm(SIGTTOU,SIG_IGN);/* ignored */
653662
#endif
654663

655664
/* ignore SIGXFSZ, so that ulimit violations work like disk full */
656665
#ifdefSIGXFSZ
657-
pqsignal(SIGXFSZ,SIG_IGN);/* ignored */
666+
pqsignal_pm(SIGXFSZ,SIG_IGN);/* ignored */
658667
#endif
659668

660669
/*
@@ -2640,7 +2649,13 @@ SIGHUP_handler(SIGNAL_ARGS)
26402649
{
26412650
intsave_errno=errno;
26422651

2652+
/*
2653+
* We rely on the signal mechanism to have blocked all signals ... except
2654+
* on Windows, which lacks sigaction(), so we have to do it manually.
2655+
*/
2656+
#ifdefWIN32
26432657
PG_SETMASK(&BlockSig);
2658+
#endif
26442659

26452660
if (Shutdown <=SmartShutdown)
26462661
{
@@ -2700,7 +2715,9 @@ SIGHUP_handler(SIGNAL_ARGS)
27002715
#endif
27012716
}
27022717

2718+
#ifdefWIN32
27032719
PG_SETMASK(&UnBlockSig);
2720+
#endif
27042721

27052722
errno=save_errno;
27062723
}
@@ -2714,7 +2731,13 @@ pmdie(SIGNAL_ARGS)
27142731
{
27152732
intsave_errno=errno;
27162733

2734+
/*
2735+
* We rely on the signal mechanism to have blocked all signals ... except
2736+
* on Windows, which lacks sigaction(), so we have to do it manually.
2737+
*/
2738+
#ifdefWIN32
27172739
PG_SETMASK(&BlockSig);
2740+
#endif
27182741

27192742
ereport(DEBUG2,
27202743
(errmsg_internal("postmaster received signal %d",
@@ -2880,7 +2903,9 @@ pmdie(SIGNAL_ARGS)
28802903
break;
28812904
}
28822905

2906+
#ifdefWIN32
28832907
PG_SETMASK(&UnBlockSig);
2908+
#endif
28842909

28852910
errno=save_errno;
28862911
}
@@ -2895,7 +2920,13 @@ reaper(SIGNAL_ARGS)
28952920
intpid;/* process id of dead child process */
28962921
intexitstatus;/* its exit status */
28972922

2923+
/*
2924+
* We rely on the signal mechanism to have blocked all signals ... except
2925+
* on Windows, which lacks sigaction(), so we have to do it manually.
2926+
*/
2927+
#ifdefWIN32
28982928
PG_SETMASK(&BlockSig);
2929+
#endif
28992930

29002931
ereport(DEBUG4,
29012932
(errmsg_internal("reaping dead processes")));
@@ -3212,7 +3243,9 @@ reaper(SIGNAL_ARGS)
32123243
PostmasterStateMachine();
32133244

32143245
/* Done with signal handler */
3246+
#ifdefWIN32
32153247
PG_SETMASK(&UnBlockSig);
3248+
#endif
32163249

32173250
errno=save_errno;
32183251
}
@@ -5114,7 +5147,13 @@ sigusr1_handler(SIGNAL_ARGS)
51145147
{
51155148
intsave_errno=errno;
51165149

5150+
/*
5151+
* We rely on the signal mechanism to have blocked all signals ... except
5152+
* on Windows, which lacks sigaction(), so we have to do it manually.
5153+
*/
5154+
#ifdefWIN32
51175155
PG_SETMASK(&BlockSig);
5156+
#endif
51185157

51195158
/* Process background worker state change. */
51205159
if (CheckPostmasterSignal(PMSIGNAL_BACKGROUND_WORKER_CHANGE))
@@ -5272,7 +5311,9 @@ sigusr1_handler(SIGNAL_ARGS)
52725311
signal_child(StartupPID,SIGUSR2);
52735312
}
52745313

5314+
#ifdefWIN32
52755315
PG_SETMASK(&UnBlockSig);
5316+
#endif
52765317

52775318
errno=save_errno;
52785319
}

‎src/include/libpq/pqsignal.h

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -36,4 +36,7 @@ extern sigset_t UnBlockSig,
3636

3737
externvoidpqinitmask(void);
3838

39+
/* pqsigfunc is declared in src/include/port.h */
40+
externpqsigfuncpqsignal_pm(intsigno,pqsigfuncfunc);
41+
3942
#endif/* PQSIGNAL_H */

‎src/include/port.h

Lines changed: 0 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -525,11 +525,6 @@ extern intpg_mkdir_p(char *path, int omode);
525525
/* port/pqsignal.c */
526526
typedefvoid (*pqsigfunc) (intsigno);
527527
externpqsigfuncpqsignal(intsigno,pqsigfuncfunc);
528-
#ifndefWIN32
529-
externpqsigfuncpqsignal_no_restart(intsigno,pqsigfuncfunc);
530-
#else
531-
#definepqsignal_no_restart(signo,func) pqsignal(signo, func)
532-
#endif
533528

534529
/* port/quotes.c */
535530
externchar*escape_single_quotes_ascii(constchar*src);

‎src/port/pqsignal.c

Lines changed: 0 additions & 29 deletions
Original file line numberDiff line numberDiff line change
@@ -58,33 +58,4 @@ pqsignal(int signo, pqsigfunc func)
5858
#endif
5959
}
6060

61-
/*
62-
* Set up a signal handler, without SA_RESTART, for signal "signo"
63-
*
64-
* Returns the previous handler.
65-
*
66-
* On Windows, this would be identical to pqsignal(), so don't bother.
67-
*/
68-
#ifndefWIN32
69-
70-
pqsigfunc
71-
pqsignal_no_restart(intsigno,pqsigfuncfunc)
72-
{
73-
structsigactionact,
74-
oact;
75-
76-
act.sa_handler=func;
77-
sigemptyset(&act.sa_mask);
78-
act.sa_flags=0;
79-
#ifdefSA_NOCLDSTOP
80-
if (signo==SIGCHLD)
81-
act.sa_flags |=SA_NOCLDSTOP;
82-
#endif
83-
if (sigaction(signo,&act,&oact)<0)
84-
returnSIG_ERR;
85-
returnoact.sa_handler;
86-
}
87-
88-
#endif/* !WIN32 */
89-
9061
#endif/* !defined(WIN32) || defined(FRONTEND) */

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp