ID: 44994
Comment by: stephen dot cuppett at sas dot com
Reported By: dbarrett at vistaprint dot com
Status: Open
Bug Type: Reproducible crash
Operating System: Windows 2003 Server, 64-bit
PHP Version: 5.2.6
New Comment:
I am also experiencing this problem. I have been able to recreate it
with system() as well as proc_open(). With proc_open() it doesn't seem
to matter if I set bypass_shell or not, just determines whether I have a
dangling cmd.exe process or not...
cmd.exe seems to stop at Wait:UserReq, but that probably doesn't mean
much.
I am able to reproduce it with XAMPP 1.6.6a (PHP 5.2.5) on Windows XP
or Windows Server 2003 (32-bit).
I don't have much to add in terms of documentation as I don't get
anything in the httpd logs, but using the following code snippet:
protected function runSAS($filename) {
$this->log("Requested to run SAS file:
" . $filename, LOG_DEBUG);
$toRun = "\"" . SAS . "\"";
$toRun .= " -sysin '" . $filename .
"'";
$toRun .= " -CONFIG '" . SASV9CFG .
"'";
$toRun .= " -PRINT '" . TEMP_DIR . "/"
. basename($filename) . ".lst'";
$toRun .= " -LOG '" . TEMP_DIR . "/" .
basename($filename) . ".log'";
$toRun .= " -NOSPLASH";
$this->log("SAS command to run: " .
$toRun, LOG_DEBUG);
$descriptorspec = array(
0 => array("pipe",
"r"), // stdin is a pipe that the child will read from
1 => array("pipe",
"w"), // stdout is a pipe that the child will write to
2 => array("pipe", "w")
// stderr is a file to write to
);
$res = proc_open($toRun,
$descriptorspec, $pipes, null, null, array(/*"bypass_shell" =>
true*/));
if (is_resource($res)) {
//fwrite($pipes[0],
"exit\n");
//fflush($pipes[0]);
fclose($pipes[0]);
fclose($pipes[1]);
fclose($pipes[2]);
$return_value =
proc_close($res);
$this->log("Return
value from SAS: " . $return_value, LOG_DEBUG);
}
}
When it does seem to complete, I'll get this in my log:
2008-06-26 20:23:55 Debug: Return value from SAS: 1
Nothing should come out on the pipes at all and when I set it up to
read those and it completes, there is no data read. However, in a hang
case, PHP blocks reading STDOUT instead of on proc_close never getting
any data... even if I set the stream to be non-blocking on the pipe
explicitely after proc_open.
Previous Comments:
------------------------------------------------------------------------
[2008-07-07 18:27:57] dbarrett at vistaprint dot com
I received a report from [EMAIL PROTECTED] that he is also
experiencing this problem. I've tried to post it several times but the
CAPTCHA is blocking it with "Please do not SPAM our bug system." I'll
keep trying.
------------------------------------------------------------------------
[2008-05-29 13:21:51] dbarrett at vistaprint dot com
I replaced all occurrences of exec() and shell_exec() in MediaWiki with
calls to a custom COM object that invokes programs. The problem went
away. This strongly suggests that PHP's implementation of exec(0 and
shell_exec() is the culprit. I suspect a race condition.
------------------------------------------------------------------------
[2008-05-14 15:09:43] dbarrett at vistaprint dot com
Description:
------------
This is an intermittent but fatal problem. I cannot reproduce it on
demand, but it occurs regularly on our MediaWiki 1.12.0 site running on
Apache 2.2.8.
When invoking a non-interactive Microsoft Windows command via exec() or
shell_exec(), sometimes the resulting process will hang. Once this
occurs, most or all subsequent exec() calls (within the same Apache
instance) will hang as well. Eventually the wiki becomes unusable. The
only way to kill these processes is to restart Apache. Other
traditional "kill" techniques fail.
This is not the same as Bug #30794, which was about interactive
commands like Notepad. I'm speaking of diverse shell commands like
perl.exe, gnuplot.exe, latex.exe, and others. All of them process text
input, if that matters.
If the process is "foo" and you run exec("foo"), you wind up with
several hung processes:
foo.exe
cmd.exe*32
This may be a race condition. I ran the "handle" utility (from
sysinternals) on the hung processes. It seemed to indicate that the
processes were waiting on c:\Apache2\logs\error.log. Then handle itself
(handle64.exe) hung!
Because this is an intermittent problem, I am looking for advice on how
to debug it and report more detailed information to you. Please don't
append the generic "install the latest snapshot and let us know if the
problem is still there" message to this ticket, because I can't install
an experimental PHP release on a production server, and the problem
happens ONLY on our production server (probably because of the load),
not on any of our development or test servers.
Expected result:
----------------
exec() and shell_exec() should never hang.
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/?id=44994&edit=1
