#46025 [Com]: zend_bailout can deadlock APC

ID: 46025 Comment by: pierre at archlinux dot de Reported By: askalski at gmail dot com Status: Suspended Bug Type: Reproducible crash Operating System: redhat PHP Version: 5.2.6 New Comment: This problem is still reproducable with version 5.2.9. The cgi version is affected, too (as expected). Previous Comments: ------------------------------------------------------------------------ [2009-02-15 00:01:20] dan at archlinux dot org Any progress here? This is definitely reproducible and we have seen it on archlinux.org about once every 3 or 4 days- it kind of stinks. Is there any current workaround besides increasing the timeout value and hoping for the best? Running: Apache 2.2.11 PHP 5.2.8 APC 3.0.19 ------------------------------------------------------------------------ [2008-09-09 00:46:09] scottmac@php.net This is essentially what http://wiki.php.net/rfc/zendsignals is for, it was considered for PHP 5.3 but has been deferred for the moment. ------------------------------------------------------------------------ [2008-09-08 23:56:04] askalski at gmail dot com Reproduced with latest checkouts from both the PHP_5_2 and PHP_5_3 tags. X-Powered-By: PHP/5.2.7-dev X-Powered-By: PHP/5.3.0alpha3-dev ------------------------------------------------------------------------ [2008-09-08 21:16:43] jani@php.net Can you reproduce this with latest CVS checkout of PHP_5_2 (and preferrably PHP_5_3) ?? ------------------------------------------------------------------------ [2008-09-08 20:50:12] askalski at gmail dot com To assist with implementing a fix: I wrote up a local fix that uses two executor globals: /* HANDLE_BLOCK_INTERRUPTIONS nesting depth */ zend_uint blocking_interruptions; /* true if a bailout was deferred while interruptions were blocked */ zend_bool deferred_bailout; In my testing, I quickly realized that APC in conjunction with Zend was making nested calls to HANDLE_BLOCK_INTERRUPTIONS(), so to keep from unblocking prematurely, it was necessary to track nesting depth. Example from my debugging: Block 0 /tmp/APC-3.0.19/php_apc.c:559 Block 1 /tmp/php-5.2.6/Zend/zend_alloc.c:1876 Unblock 1 /tmp/php-5.2.6/Zend/zend_alloc.c:1913 Unblock 0 /tmp/APC-3.0.19/php_apc.c:592 My updated macros: #define HANDLE_BLOCK_INTERRUPTIONS() if (!EG(blocking_interruptions)++) { if (zend_block_interruptions) { zend_block_interruptions(); } } #define HANDLE_UNBLOCK_INTERRUPTIONS() if (EG(blocking_interruptions) && !--EG(blocking_interruptions)) { if (zend_unblock_interruptions) { zend_unblock_interruptions(); } if (EG(deferred_bailout)) { zend_bailout(); } } And my mod to _zend_bailout: if (EG(blocking_interruptions)) { EG(deferred_bailout) = 1; return; } EG(deferred_bailout) = 0; ------------------------------------------------------------------------ The remainder of the comments for this report are too long. To view the rest of the comments, please view the bug report online at http://bugs.php.net/46025 -- Edit this bug report at http://bugs.php.net/?id=46025&edit=1