#47227 [Bgs]: children forked with pcntl_fork release flock()s created by parent

ID: 47227 User updated by: murphyk at yahoo-inc dot com Reported By: murphyk at yahoo-inc dot com Status: Bogus Bug Type: PCNTL related Operating System: RHEL 4.4 PHP Version: 5.2.8 New Comment: I have RTFM, thanks. From the man 2 flock: "Locks created by flock() are associated with a file, or, more precisely, an open file table entry. This means that duplicate file descriptors (created by, for example, fork(2) or dup(2)) refer to the same lock, and this lock may be modified or released using any of these descriptors. Furthermore, the lock is released either by an explicit LOCK_UN operation on any of these duplicate descriptors, or when all such descriptors have been closed." "by an explicit LOCK_UN" - my child process did NOT call flock() in my user code. "or when all such descriptors have been closed" - my parent process still has an open copy of the the filehandle. To be clear, the "expected result" output is what happens in php4 - the child closes the filehandle, but doesn't unlock the flock(). php5 appears to be explicitly unlocking all held flocks() during shutdown. If this is intentional, fine, but it's not documented, and it's a change in behavior between php4 and php5 which breaks previously running code. Previous Comments: ------------------------------------------------------------------------ [2009-01-28 08:44:50] jani@php.net RTFM: man 2 flock man 2 fork The behaviour is exactly how it should be and is. ------------------------------------------------------------------------ [2009-01-27 22:07:47] murphyk at yahoo-inc dot com Description: ------------ The behavior of flock()ed files across forks appears to have changed between php 4.4.8 and php 5.2.8. Previously, children would inherit filehandles from their parent, and would close() their copies of the filehandles on exit, but this would not clear flock()s on the files locked in the parent. Now, it appears that if any child exits(), this will clear flock()s on any filehandles inherited from the parent. Reproduce code: --------------- <?php $fp = fopen("/tmp/lock.txt", "w+"); if (flock($fp, LOCK_EX + LOCK_NB )) { print "Got lock.\n"; } else { print "Couldn't lock the file.\n"; exit(); } $pid = pcntl_fork(); if ($pid) { pcntl_waitpid($pid,$status); } else { exit(); } sleep(100); ?> Expected result: ---------------- $ php flock.php & [1] 22054 $ Got lock. $ php flock.php Couldn't lock the file. Actual result: -------------- $php flock.php & [1] 31085 $Got lock. $php flock.php Got lock. ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=47227&edit=1