Bug #79412 [NEW]: Opcache chokes and uses 100% CPU on specific script

From: bugs at rudeirer dot wtf Operating system: Debian 10 (amd64) PHP version: 7.4.4 Package: opcache Bug Type: Bug Bug description:Opcache chokes and uses 100% CPU on specific script Description: ------------ I observed several non-responding FPM worker processes using 100% CPU. Attaching gdb and printing a stack trace indicated that the issue might be with opcache. In /proc/PID/fd, it could be seen that all affected processes had opened a specific file. Disabling opcache or blacklisting the file worked around the problem. By trial and error, I removed lines from the problematic file in order to produce a short test script. The code is not runnable any more, but it's small and still causes the problem. (In the original code, all referenced variables were properly defined.) I originally encountered this problem while using PHP 7.3.14 as supplied by Debian, so I believe 7.3 is also affected. For testing, I downloaded and compiled PHP 7.4.4 in a clean Debian 10 chroot. The configure line was "./configure --enable-debug --prefix=/opt/php/7.4.4". No changes were made to php.ini or any other file. Saving the test script as "bug.php" and running it with "php -d zend_extension=opcache.so -d opcache.enable_cli=1 bug.php" exhibits the problematic behavior. This is a stack trace obtained after letting php run the test script for a few seconds: #0 0x00007f3c0717639b in zend_infer_ranges (op_array=0x7f3c07277008, ssa=0x7f3c07286028) at /home/build/php-7.4.4/ext/opcache/Optimizer/zend_inference.c:1815 #1 0x00007f3c0719268d in zend_ssa_inference (arena=0x7ffc6c37df10, op_array=0x7f3c07277008, script=0x7f3c07277000, ssa=0x7f3c07286028, optimization_level=2147401727) at /home/build/php-7.4.4/ext/opcache/Optimizer/zend_inference.c:4330 #2 0x00007f3c0715ee7a in zend_dfa_analyze_op_array (op_array=0x7f3c07277008, ctx=0x7ffc6c37df10, ssa=0x7f3c07286028) at /home/build/php-7.4.4/ext/opcache/Optimizer/dfa_pass.c:113 #3 0x00007f3c07142fdb in zend_optimize_script (script=0x7f3c07277000, optimization_level=2147401727, debug_level=0) at /home/build/php-7.4.4/ext/opcache/Optimizer/zend_optimizer.c:1382 #4 0x00007f3c071113f8 in cache_script_in_shared_memory (new_persistent_script=0x7f3c07277000, key=0x7f3c071d6da4 <accel_globals+484> "bug.php:2274224:2220784", key_length=23, from_shared_memory=0x7ffc6c37e220) at /home/build/php-7.4.4/ext/opcache/ZendAccelerator.c:1451 #5 0x00007f3c071132da in persistent_compile_file (file_handle=0x7ffc6c381810, type=8) at /home/build/php-7.4.4/ext/opcache/ZendAccelerator.c:2136 #6 0x0000563a74674bf5 in zend_execute_scripts (type=8, retval=0x0, file_count=3) at /home/build/php-7.4.4/Zend/zend.c:1659 #7 0x0000563a745dd9dd in php_execute_script (primary_file=0x7ffc6c381810) at /home/build/php-7.4.4/main/main.c:2617 #8 0x0000563a7474a481 in do_cli (argc=6, argv=0x563a767e78c0) at /home/build/php-7.4.4/sapi/cli/php_cli.c:961 #9 0x0000563a7474b451 in main (argc=6, argv=0x563a767e78c0) at /home/build/php-7.4.4/sapi/cli/php_cli.c:1356 Test script: --------------- <?php $limitPerRun = 10; foreach ($foo as $bar) { $count = 0; foreach ($runs as $run) { ++$count; if ($count >= $limitPerRun) { break; } } foo($limitPerRun); } -- Edit bug report at https://bugs.php.net/bug.php?id=79412&edit=1 -- Fix committed: https://bugs.php.net/fix.php?id=79412&r=fixed Fixed in release: https://bugs.php.net/fix.php?id=79412&r=alreadyfixed Need backtrace: https://bugs.php.net/fix.php?id=79412&r=needtrace Need Reproduce Script: https://bugs.php.net/fix.php?id=79412&r=needscript Try newer version: https://bugs.php.net/fix.php?id=79412&r=oldversion Not developer issue: https://bugs.php.net/fix.php?id=79412&r=support Expected behavior: https://bugs.php.net/fix.php?id=79412&r=notwrong Not enough info: https://bugs.php.net/fix.php?id=79412&r=notenoughinfo Submitted twice: https://bugs.php.net/fix.php?id=79412&r=submittedtwice register_globals: https://bugs.php.net/fix.php?id=79412&r=globals PHP version support discontinued: https://bugs.php.net/fix.php?id=79412&r=phptooold Daylight Savings: https://bugs.php.net/fix.php?id=79412&r=dst IIS Stability: https://bugs.php.net/fix.php?id=79412&r=isapi Install GNU Sed: https://bugs.php.net/fix.php?id=79412&r=gnused Floating point limitations: https://bugs.php.net/fix.php?id=79412&r=float No Zend Extensions: https://bugs.php.net/fix.php?id=79412&r=nozend MySQL Configuration Error: https://bugs.php.net/fix.php?id=79412&r=mysqlcfg