[perl #24537] HP-UX 11.00 -- SA_RESTART not allowing EINTR through to select

On Fri Nov 21 07:42:11 2003, chaimf@pobox.com wrote:
> This is a bug report for perl from chaimf@pobox.com
> generated with the help of perlbug 1.34 running under perl v5.8.2.
> 
> The select call does not notice every SIGCHILD.
> 
> Even with a sigaction turning off SA_RESTART on SIGCHLD it only reacts
>    after
> all the children are done.
> 
> I need to be able to notice each SIGCHLD while waiting in a select
>    call.
> 
> I have been unable to reproduce the action in c code. In the c code,
>    if
> SA_RESTART is off, each SIGCHLD causes the select to return with
>    EINTR.
> 
> ---[output]---
> [29785]: doit: current handler is: main::c
> [29785]: started pid=29786
> [29786]: Sleeping for a while
> [29787]: Sleeping for a while
> [29785]: started pid=29787
> [29785]: Waiting in select
> [29787]: Awoken. Will leave nastily
> Illegal division by zero at ./child.pl line 46.
> [29785]: sa_handler invoked <CHLD>
> [29785]: reaping child.
> [29785]: pid 29787 - ret(255) signal(0) dumped(0)
> 				<<
> 				<< I expect a Select returned -1 here
>     				<<
> [29786]: Awoken. Will leave nicely
> [29785]: pid 29786 - ret(0) signal(0) dumped(0)
> [29785]: sa_handler invoked <CHLD>
> [29785]: reaping child.
> [29785]: Select returned -1 left=10
> [29785]: Waiting in select
> [29785]: Select returned 0 left=10
> [29785]: Waiting in select
> [29785]: Select returned 0 left=10
> [29785]: Waiting in select
> [29785]: Select returned 0 left=10
> 
> 
> ---[Code]---
> #!/u1/bea/cfx/perl5/bin/perl -w
> 
> $| = 1;
> 
> 
> use POSIX qw(:signal_h :fcntl_h :sys_stat_h :sys_wait_h :time_h);
> sub c()
> {
> 	print "[$$]: sa_handler invoked <", join(",", @_), ">\n";
> 	print "[$$]: reaping child.\n";
> 	while (-1 != ($somePid = waitpid(-1, 0)  )) {
> 		$status = $?;
> 		print "[$$]: pid $somePid - ret(", $status >>8
> 		    , ") signal(", $status & 127
> 		      ,") dumped(", $status & 128
> 			,")\n";
> 	}
> }
> 
> sub turnoff_sarestart
> {
>     my $sigact = POSIX::SigAction->new('DEFAULT');
>     my $newsig = POSIX::SigAction->new('DEFAULT');
> 
>     sigaction(SIGCHLD, $sigact, $newsig);		# get the value
>     $newsig->{FLAGS} &= ~SA_RESTART;			# Turn off SA_RESTART
>     sigaction(SIGCHLD, $newsig, $sigact);		# get the value
> }
> 
> sub startem
> {
> 	unless ($pid = fork) {
> 		print "[$$]: Sleeping for a while\n";
> 		sleep(5);
> 		print "[$$]: Awoken. Will leave nicely\n";
> 		exit 0;
> 	}
> 
> 	print "[$$]: started pid=$pid\n";
> 
> 	unless ($pid = fork) {
> 		print "[$$]: Sleeping for a while\n";
> 		sleep(2);
> 		print "[$$]: Awoken. Will leave nastily\n";
> 		$foo = 1; $bar = 0;
> 		print $foo / $bar;
> 		exit 1;
> 	}
> 	print "[$$]: started pid=$pid\n";
> }
> 
> sub doit
> {
> 	$SIG{CHLD} = "c";
> 	&turnoff_sarestart;
> 
> 	print "[$$]: doit: current handler is: $SIG{CHLD}\n";
> 
> 	startem;
> 
> 	for (0..3) {
> 		print "[$$]: Waiting in select\n";
> 		$r = $w = $e = "";
> 		($ret,$left) = select($r, $w, $e, 10);
> 		print "[$$]: Select returned $ret left=$left\n";
> 	}
> }
> 
> 
> &doit;
> exit 0;

Hugmeir reported on #p5p tonight, "I can reproduce this in HP-UX, Linux,
and OpenBSD. I don't know the first thing about signals, so could
someone check if this actually a bug?"

I know just as little about signals.  I reproduced the problem on Darwin
with a version of chaimf's program (attached) cleaned up a bit to run
under 'use strict'.

Thank you very much.
Jim Keenan

---
via perlbug:  queue: perl5 status: new
https://rt.perl.org:443/rt3/Ticket/Display.html?id=24537

• [perl #24537] HP-UX 11.00 -- SA_RESTART not allowing EINTR through to select by James E Keenan via RT
• Re: [perl #24537] HP-UX 11.00 -- SA_RESTART not allowing EINTRthrough to select by Leon Timmermans