[pgpool-hackers: 49] Re: [pgpool-II 0000009]: dont call syslog(3) family in signal handler.

[Tatsuo Ishii]

Hi,

A fundamental problem with syslog support has been reported to the bug
track. Syslog support was introduced in 3.1:

>	  - Add syslog support. Patch contributed by Gilles Darold. Review and
>		editing by Guillaume Lelarge.

Problem is, syslog support implementation is just replacing vsprintf
etc. like this:

	/* Write error message to syslog */
	if (pool_config->logsyslog == 1) {
	   va_start(ap, fmt);
	   vsyslog(pool_config->syslog_facility | LOG_ERR, fmt, ap);
	   va_end(ap);
	   return;
	}

So if pool_log() or pool_debug() etc. is called within a signal
handler, it causes a serious problem as reported in the bug track.
(please note that calling pool_log or pool_debug with syslog support
disabled is safe).

Any idea better than dropping the syslog support to fix this?
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese: http://www.sraoss.co.jp

From: pgpool Bug Tracker <bugtracker at pgpool.net>
Subject: [pgpool-II 0000009]: dont call syslog(3) family in signal handler.
Date: Tue, 27 Mar 2012 18:23:39 +0900
Message-ID: <096846c6f220607be9fa757c536ca1b8 at www.pgpool.net>

> 
> The following issue has been SUBMITTED. 
> ====================================================================== 
> http://www.pgpool.net/mantisbt/view.php?id=9 
> ====================================================================== 
> Reported By:                harukat
> Assigned To:                
> ====================================================================== 
> Project:                    pgpool-II
> Issue ID:                   9
> Category:                   Bug
> Reproducibility:            sometimes
> Severity:                   block
> Priority:                   high
> Status:                     new
> ====================================================================== 
> Date Submitted:             2012-03-27 18:23 JST
> Last Modified:              2012-03-27 18:23 JST
> ====================================================================== 
> Summary:                    dont call syslog(3) family in signal handler.
> Description: 
> Dont call syslog(3) family in signal handler.
> it causes process deadlock.
> 
> /* signal handler for SIGALRM */
> static RETSIGTYPE authentication_timeout(int sig)
> {
>     pool_log("authentication is timeout");
>     child_exit(1);
> }
> 
> # gstack 12345
> http://www.pgpool.net/mantisbt/view.php?id=0  0x000000303b2f508e in
> __lll_lock_wait_private () from /lib64/libc.so.6
> http://www.pgpool.net/mantisbt/view.php?id=1  0x000000303b2e22a8 in _L_lock_798
> () from /lib64/libc.so.6
> http://www.pgpool.net/mantisbt/view.php?id=2  0x000000303b2e1d72 in
> __vsyslog_chk () from /lib64/libc.so.6
> http://www.pgpool.net/mantisbt/view.php?id=3  0x000000000041232c in pool_log ()
> http://www.pgpool.net/mantisbt/view.php?id=4  0x0000000000408b20 in
> authentication_timeout ()
> http://www.pgpool.net/mantisbt/view.php?id=5  <signal handler called>
> http://www.pgpool.net/mantisbt/view.php?id=6  0x000000303b2e6812 in send () from
> /lib64/libc.so.6
> http://www.pgpool.net/mantisbt/view.php?id=7  0x000000303b2e1e80 in
> __vsyslog_chk () from /lib64/libc.so.6
> http://www.pgpool.net/mantisbt/view.php?id=8  0x000000000041232c in pool_log ()
> http://www.pgpool.net/mantisbt/view.php?id=9  0x0000000000409872 in do_accept ()
> http://www.pgpool.net/mantisbt/view.php?id=10 0x0000000000409b5b in do_child ()
> http://www.pgpool.net/mantisbt/view.php?id=11 0x0000000000404085 in fork_a_child
> ()
> http://www.pgpool.net/mantisbt/view.php?id=12 0x00000000004059bc in reaper ()
> http://www.pgpool.net/mantisbt/view.php?id=13 0x00000000004073c3 in main ()
> 
> Additional Information: 
> pgpool-II 3.1.3
> ====================================================================== 
> 
> Issue History 
> Date Modified    Username       Field                    Change               
> ====================================================================== 
> 2012-03-27 18:23 harukat        New Issue                                    
> ======================================================================
>