From: bugs dot php dot net at chsc dot dk
Operating system: Linux
PHP version: 5.0.5
PHP Bug Type: Directory function related
Bug description: Concurrency issue with recursive mkdir
Description:
------------
There appears to be a concurrency issue when mkdir is called on two
separate threads with the following parameters:
Thread 1:
mkdir('/tmp/foo/bar/1', 0777, true);
Thread 2:
mkdir('/tmp/foo/bar/2', 0777, true);
Sometimes one of the threads (e.g. thread 2) two fails with "Warning:
mkdir(): File exists" and the directory /tmp/foo/bar/2 does not exist
afterwards.
What I think is happening in thread 2 is is this:
PHP looks for /tmp/foo/bar/2 and sees that it does not exist. Neither does
/tmp/foo/bar and /tmp/foo. So it tries to create /tmp/foo, but that
directory was just created a millisecond second ago by another thread, so
mkdir gives instead of just moving on to create /tmp/foo/bar and
/tmp/foo/bar/2.
Reproduce code:
---------------
This code reproduces the problem in about every second attempt. It
consists of two files, index.php and iframe.php.
index.php:
<?php
$fire = time() + 2;
?>
<h1>Nr. 1</h1>
<iframe src="iframe.php?fire=<?= $fire ?>&no=1"></iframe>
<h1>Nr. 2</h1>
<iframe src="iframe.php?fire=<?= $fire ?>&no=2"></iframe>
iframe.php:
<?php
$fire = $_GET['fire'];
$no = $_GET['no'];
// synchronize the two threads
while ($fire > time());
$dir = '/tmp/' . $fire . '/foo/bar/foo/bar/' . $no;
//sleep($no);
var_dump(is_dir($dir));
echo "Making $dir ";
mkdir($dir, 0777, true);
var_dump(is_dir($dir));
?>
Expected result:
----------------
Thread 2 should output this:
bool(false) Making /tmp/1132653651/foo/bar/foo/bar/2 bool(true)
Actual result:
--------------
Thread 2 sometimes outputs this:
bool(false) Making /tmp/1132655181/foo/bar/foo/bar/2 Warning: mkdir():
File exists in /home/chsc/public_html/mkdir/iframe.php on line 10
bool(false)
Notice that the directory does not exist afterwards.
If I uncomment the sleep() call above, there are no problems.
A workaround:
$ok = mkdir($dir, 0777, true);
if (!$ok && !is_dir($dir)) {
sleep(1);
mkdir($dir, 0777, true);
}
In other words, it works if I try again. I hope that mkdir() can be
changed so that it only returns false if the directory cannot be created
at all (e.g. because of lack of permissions or because it already
exists).
--
Edit bug report at http://bugs.php.net/?id=35326&edit=1
--
Try a CVS snapshot (php4): http://bugs.php.net/fix.php?id=35326&r=trysnapshot4
Try a CVS snapshot (php5.0):
http://bugs.php.net/fix.php?id=35326&r=trysnapshot50
Try a CVS snapshot (php5.1):
http://bugs.php.net/fix.php?id=35326&r=trysnapshot51
Fixed in CVS: http://bugs.php.net/fix.php?id=35326&r=fixedcvs
Fixed in release: http://bugs.php.net/fix.php?id=35326&r=alreadyfixed
Need backtrace: http://bugs.php.net/fix.php?id=35326&r=needtrace
Need Reproduce Script: http://bugs.php.net/fix.php?id=35326&r=needscript
Try newer version: http://bugs.php.net/fix.php?id=35326&r=oldversion
Not developer issue: http://bugs.php.net/fix.php?id=35326&r=support
Expected behavior: http://bugs.php.net/fix.php?id=35326&r=notwrong
Not enough info:
http://bugs.php.net/fix.php?id=35326&r=notenoughinfo
Submitted twice:
http://bugs.php.net/fix.php?id=35326&r=submittedtwice
register_globals: http://bugs.php.net/fix.php?id=35326&r=globals
PHP 3 support discontinued: http://bugs.php.net/fix.php?id=35326&r=php3
Daylight Savings: http://bugs.php.net/fix.php?id=35326&r=dst
IIS Stability: http://bugs.php.net/fix.php?id=35326&r=isapi
Install GNU Sed: http://bugs.php.net/fix.php?id=35326&r=gnused
Floating point limitations: http://bugs.php.net/fix.php?id=35326&r=float
No Zend Extensions: http://bugs.php.net/fix.php?id=35326&r=nozend
MySQL Configuration Error: http://bugs.php.net/fix.php?id=35326&r=mysqlcfg
