ID: 16986 Updated by: [EMAIL PROTECTED] Reported By: [EMAIL PROTECTED] -Status: Feedback +Status: Open Bug Type: Semaphore related Operating System: Linux 2.4.18 PHP Version: 4.1.2 New Comment:
It cause deadlock, but only on the script... if you test your script and have a deadlock, you fix it and release the sem you forgot. I think the auto release may be a good DEFAULT, but it is important to be able to modify this behaviour. If you want to fulfill any classical IPC problem (see Tanenbuam!) You have to be able to acquire a sem, and not to realease it. Here you ca nfind an explanation of the problems one can have and that auto release make impossible to solve: http://joda.cis.temple.edu/~ingargio/old/cis307f95/readings/readwriters.html Previous Comments: ------------------------------------------------------------------------ [2002-05-03 06:47:10] [EMAIL PROTECTED] But a process that acquires a semaphore and then exits will case deadlocks, because no one else can acquire the semaphore?? Can you give a good example of where leaving the semaphore acquired is actually useful? ------------------------------------------------------------------------ [2002-05-03 05:37:33] [EMAIL PROTECTED] sem_acquire() function has this behavior: After processing a request, any semaphores acquired by the process but not explicitly released will be released automatically and a warning will be generated. This is not a great thing, infact in this way the readers/writers classical IPC problem, with writers precedence is impossible to implement !!! I think an option to disable autorelease is usefull. (I sent a feature/change request, but I had no feadback :-( ) ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=16986&edit=1
