#49010 [Opn]: spl_object_hash not unique for Objects used in concurrent (forked) environment

ID: 49010 User updated by: benjamin at josefus dot net Reported By: benjamin at josefus dot net Status: Open Bug Type: SPL related Operating System: Ubuntu 9.04, Kernel2.6.27 PHP Version: 5.3SVN-2009-07-21 (snap) New Comment: This is the result with spl_object_hash() invoked first off (as it should be): not yet shared, initialize SHM 0000000016c4f93000000000506bf64a Worker: --> Wait!, ID: 0000000016c4f93000000000506bf64a Producer: --> Producing 0, ID: 0000000016c4f93000000000506bf64a Worker: --> Working on 0, ID: 0000000016c4f93000000000506bf64a Producer: --> Producing 1, ID: 0000000016c4f93000000000506bf64a Worker: --> Working on 1, ID: 0000000016c4f93000000000506bf64a Producer: --> Producing 2, ID: 0000000016c4f93000000000506bf64a Worker: --> Working on 2, ID: 0000000016c4f93000000000506bf64a Producer: --> Producing 3, ID: 0000000016c4f93000000000506bf64a Worker: --> Working on 3, ID: 0000000016c4f93000000000506bf64a Producer: --> Producing 4, ID: 0000000016c4f93000000000506bf64a Worker: --> Working on 4, ID: 0000000016c4f93000000000506bf64a Worker: --> Wait!, ID: 0000000016c4f93000000000506bf64a Producer: --> Producing 5, ID: 0000000016c4f93000000000506bf64a Worker: --> Working on 5, ID: 0000000016c4f93000000000506bf64a Producer: --> Producing 6, ID: 0000000016c4f93000000000506bf64a Worker: --> Working on 6, ID: 0000000016c4f93000000000506bf64a Producer: --> Producing 7, ID: 0000000016c4f93000000000506bf64a Worker: --> Working on 7, ID: 0000000016c4f93000000000506bf64a Producer: --> Producing 8, ID: 0000000016c4f93000000000506bf64a Worker: --> Working on 8, ID: 0000000016c4f93000000000506bf64a Producer: --> Producing 9, ID: 0000000016c4f93000000000506bf64a Worker: --> Working on 9, ID: 0000000016c4f93000000000506bf64a This one happens when spl_object_hash() has not been invoked first off: not yet shared, initialize SHM 0000000051f9a9a50000000056018292 not yet shared, initialize SHM 00000000187ccfd60000000067032181 Worker: --> Wait!, ID: 00000000187ccfd60000000067032181 Producer: --> Producing 0, ID: 0000000051f9a9a50000000056018292 Worker: --> Wait!, ID: 00000000187ccfd60000000067032181 Producer: --> Producing 1, ID: 0000000051f9a9a50000000056018292 Worker: --> Wait!, ID: 00000000187ccfd60000000067032181 Producer: --> Producing 2, ID: 0000000051f9a9a50000000056018292 Worker: --> Wait!, ID: 00000000187ccfd60000000067032181 Producer: --> Producing 3, ID: 0000000051f9a9a50000000056018292 Worker: --> Wait!, ID: 00000000187ccfd60000000067032181 Producer: --> Producing 4, ID: 0000000051f9a9a50000000056018292 Worker: --> Wait!, ID: 00000000187ccfd60000000067032181 Producer: --> Producing 5, ID: 0000000051f9a9a50000000056018292 Worker: --> Wait!, ID: 00000000187ccfd60000000067032181 Worker: --> Wait!, ID: 00000000187ccfd60000000067032181 Producer: --> Producing 6, ID: 0000000051f9a9a50000000056018292 Worker: --> Wait!, ID: 00000000187ccfd60000000067032181 Producer: --> Producing 7, ID: 0000000051f9a9a50000000056018292 Worker: --> Wait!, ID: 00000000187ccfd60000000067032181 Producer: --> Producing 8, ID: 0000000051f9a9a50000000056018292 Producer: --> Producing 9, ID: 0000000051f9a9a50000000056018292 Previous Comments: ------------------------------------------------------------------------ [2009-07-21 20:54:56] benjamin at josefus dot net Description: ------------ I am working on a Task Management (java-like Threads) where each Task implements a pcntl_fork(), which works with shared Objects using IPC and Semaphore to access concurrently and synchronized. The Synchronisation should happen by unique Key per Object and SHM Segment (delivered by spl_object_hash). I am using sem_acquire(), sem_release(), shm_attach(), shm_release(), shm_[put|get]_var() and so on. When providing two concurrent Tasks with the same Object to be shared, spl_object_hash delivers two different Hashes, when invoked in each Task. Interestingly, if i call spl_object_hash for the shared Object before it is assigned to both "Producer" and "Worker" Task, the Hash IS unique, as it should be! In short: - new Object - fork -> spl_object_hash(Object) is NOT unique - new Object - call spl_object_hash(Object) first off - fork -> spl_object_hash(Object) IS unique and correct System Notes: PHP 5.3.0 (cli) (built: Jul 21 2009 22:19:17) Configure Command './configure' '--enable-pcntl' '--enable-shmop' '--enable-sysvmsg' '--enable-sysvsem' '--enable-sysvshm' '--with-apxs2=/usr/bin/apxs2' '--disable-short-tags' '--with-openssl' '--with-zlib' '--enable-bcmath' '--with-bz2=/bin/bzip2' '--enable-calendar' '--with-curl' '--with-curlwrappers' '--enable-exif' '--enable-ftp' '--with-gd' '--with-jpeg-dir=/usr/lib' '--with-png-dir=/usr/lib' '--with-xpm-dir=/usr/lib' '--with-t1lib' '--enable-gd-native-ttf' '--enable-gd-jis-conv' '--with-gettext' '--with-imap' '--with-imap-ssl' '--with-ldap' '--with-ldap-sasl' '--enable-mbstring' '--with-mcrypt' '--with-mhash' '--with-mysql=mysqlnd' '--with-mysqli=mysqlnd' '--with-pdo-mysql' '--with-pspell' '--with-readline' '--with-snmp' '--enable-soap' '--enable-sockets' '--without-sqlite' '--enable-sqlite-utf8' '--with-tidy' '--enable-wddx' '--with-xmlrpc' '--with-xsl' '--enable-zip' '--with-pear' '--with-kerberos' '--with-pgsql' '--with-pdo-pgsql' Reproduce code: --------------- $shared = new MySharedObj(); spl_object_hash($shared); //toggle this line to for in/correct result /** * $shared is referenced member variable in each task */ $producer = new ProducerTask($shared); $worker = new WorkerTask($shared); $producer->start(); $worker->start(); //outputs different Hash for $shared provided by spl_object_hash ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=49010&edit=1