#35894 [Fbk->Opn]: php-imap doesn't trap USR2 when mailbox is locked
ID: 35894 User updated by: jik at kamens dot brookline dot ma dot us Reported By: jik at kamens dot brookline dot ma dot us -Status: Feedback +Status: Open Bug Type: IMAP related Operating System: Linux PHP Version: 5.1.1 New Comment: You *don't* want to allow the simultaneous opening of a mailbox by two processes. The whole point of locking is to *prevent* the simultaneous opening of a mailbox by two processes. What the locking is *supposed* to do is to make one process *wait* for the other one, but what it does instead, if you don't catch the USR2 signal, is for the process that got the lock first to *die* after *being killed* by the other one. This is not correct behavior. Incidentally, I just tested with a newly compiled c-client 2004g and confirmed that the problem persists there without my patch. Previous Comments: [2006-01-05 10:07:30] [EMAIL PROTECTED] Why would you want to allow opening same mailbox by two simultaneous processes? [2006-01-05 04:13:45] jik at kamens dot brookline dot ma dot us Please look carefully at the output. The notices are not "harmless". Note that the message "successfully opened mailbox" only appears *once*. It should appear twice, because there are two processes who both want to open the mailbox. It only appears once because one of the two processes is killed by a USR2 signal as I've described. I don't know why the patch I sent didn't help for you. It reliably solves the problem for me. Perhaps I picked bad preprocessor symbols and it's not actually getting compiled into the object code on your system. Can you put debugging code in to see if the arm_signal calls are actually happening? Thanks. [2006-01-05 01:01:06] [EMAIL PROTECTED] I get the same notices, which seem quite harmless anyway. And your patch did not make any difference whatsoever. [2006-01-04 21:53:23] jik at kamens dot brookline dot ma dot us libc-client-2002e-18.1 RPM from Fedora Core. I checked the current c-client sources from washington.edu and they seem susceptible to this problem as well, judging from an examination of the source code. The USR2 functionality has been in c-client since 1993, as far as I can tell. [2006-01-04 21:49:48] [EMAIL PROTECTED] Exactly what c-client version you linked PHP with? And how was it compiled? 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/35894 -- Edit this bug report at http://bugs.php.net/?id=35894&edit=1
#35894 [Fbk->Opn]: php-imap doesn't trap USR2 when mailbox is locked
ID: 35894 User updated by: jik at kamens dot brookline dot ma dot us Reported By: jik at kamens dot brookline dot ma dot us -Status: Feedback +Status: Open Bug Type: IMAP related Operating System: Linux PHP Version: 5.1.1 New Comment: libc-client-2002e-18.1 RPM from Fedora Core. I checked the current c-client sources from washington.edu and they seem susceptible to this problem as well, judging from an examination of the source code. The USR2 functionality has been in c-client since 1993, as far as I can tell. Previous Comments: [2006-01-04 21:49:48] [EMAIL PROTECTED] Exactly what c-client version you linked PHP with? And how was it compiled? [2006-01-04 21:14:14] jik at kamens dot brookline dot ma dot us There's a patch which makes this problem go away at http://stuff.mit.edu/~jik/php-5.1.1-imap-usr2.patch.txt. However, rather than using the #if statement I used to figure out whether to enable the relevant code, you may want to insert a check for the function arm_signal in the c-client library in the configure script, define a cpp symbol if the function exists, and use my code if that cpp symbol is defined. [2006-01-04 19:59:55] [EMAIL PROTECTED] >Did you run the script twice at the same time as I said in my report? Yes. And the mailbox is not empty. [2006-01-04 19:53:02] jik at kamens dot brookline dot ma dot us Also, let me remind you that it won't happen if the mailbox file is empty; it needs to have messages in it, or c-client won't lock it. [2006-01-04 19:52:09] jik at kamens dot brookline dot ma dot us Did you run the script twice at the same time as I said in my report? That's the only way you're going to be able to reproduce it, since it requires contention from two different processes. 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/35894 -- Edit this bug report at http://bugs.php.net/?id=35894&edit=1
#35894 [Fbk->Opn]: php-imap doesn't trap USR2 when mailbox is locked
ID: 35894 User updated by: jik at kamens dot brookline dot ma dot us Reported By: jik at kamens dot brookline dot ma dot us -Status: Feedback +Status: Open Bug Type: IMAP related Operating System: Linux PHP Version: 5.1.1 New Comment: There's a patch which makes this problem go away at http://stuff.mit.edu/~jik/php-5.1.1-imap-usr2.patch.txt. However, rather than using the #if statement I used to figure out whether to enable the relevant code, you may want to insert a check for the function arm_signal in the c-client library in the configure script, define a cpp symbol if the function exists, and use my code if that cpp symbol is defined. Previous Comments: [2006-01-04 19:59:55] [EMAIL PROTECTED] >Did you run the script twice at the same time as I said in my report? Yes. And the mailbox is not empty. [2006-01-04 19:53:02] jik at kamens dot brookline dot ma dot us Also, let me remind you that it won't happen if the mailbox file is empty; it needs to have messages in it, or c-client won't lock it. [2006-01-04 19:52:09] jik at kamens dot brookline dot ma dot us Did you run the script twice at the same time as I said in my report? That's the only way you're going to be able to reproduce it, since it requires contention from two different processes. [2006-01-04 19:51:27] jik at kamens dot brookline dot ma dot us $ ls -l /var/mail/jik; php /tmp/imap_open.php /var/mail/jik & php /tmp/imap_open.php /var/mail/jik -rw--- 1 jik mail 871 Jan 4 13:44 /var/mail/jik [1] 31702 starting to open mailbox starting to open mailbox successfully opened mailbox PHP Notice: Unknown: Trying to get mailbox lock from process 31702 (errflg=1) in Unknown on line 0 [1]+ User defined signal 2 php /tmp/imap_open.php /var/mail/jik $ New version of the script: I don't know why you can't reproduce it; it reproduces easily for me, as shown above. The c-client documentation and source code make it clear that this is going on, so unless you can confirm that PHP is installing a USR2 handle when locking mailboxes, I'm pretty sure it's a problem. [2006-01-04 19:33:42] [EMAIL PROTECTED] Can't reproduce. I don't see any error messages and the script works fine. 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/35894 -- Edit this bug report at http://bugs.php.net/?id=35894&edit=1
#35894 [Fbk->Opn]: php-imap doesn't trap USR2 when mailbox is locked
ID: 35894 User updated by: jik at kamens dot brookline dot ma dot us Reported By: jik at kamens dot brookline dot ma dot us -Status: Feedback +Status: Open Bug Type: IMAP related Operating System: Linux PHP Version: 5.1.1 New Comment: $ ls -l /var/mail/jik; php /tmp/imap_open.php /var/mail/jik & php /tmp/imap_open.php /var/mail/jik -rw--- 1 jik mail 871 Jan 4 13:44 /var/mail/jik [1] 31702 starting to open mailbox starting to open mailbox successfully opened mailbox PHP Notice: Unknown: Trying to get mailbox lock from process 31702 (errflg=1) in Unknown on line 0 [1]+ User defined signal 2 php /tmp/imap_open.php /var/mail/jik $ New version of the script: I don't know why you can't reproduce it; it reproduces easily for me, as shown above. The c-client documentation and source code make it clear that this is going on, so unless you can confirm that PHP is installing a USR2 handle when locking mailboxes, I'm pretty sure it's a problem. Previous Comments: [2006-01-04 19:33:42] [EMAIL PROTECTED] Can't reproduce. I don't see any error messages and the script works fine. [2006-01-04 15:48:59] jik at kamens dot brookline dot ma dot us Woops, forgot the script. Here it is: You probably could have figured this out :-). You need an mbox file on which to run imap_open; there's no way to eliminate that dependency. [2006-01-04 15:40:29] jik at kamens dot brookline dot ma dot us Description: The imap c-client has code in it to send a "kiss of death" SIGUSR2 to another process that has a mailbox locked, to cause that process to give up the lock if it no longer needs it. Anything which uses c-client is supposed to define a singla handler for SIGUSR2 to catch the signal and at minimum ignore it if the client doesn't want to relinquish the lock. If it doesn't do this, then the SIGUSR2 causes the process to die, and then the other process, which sent the signal, claims the lock. It appears that PHP's imap support doesn't define a SIGUSR2 handler, which means that if (a) imap_open is used to open a local file and (b) another process on the same machine happens to use c-client to open the same file at around the same time, the first process will die silently because of the SIGUSR2. To fix this, imap_open needs to define a SIGUSR2 handler to catch and ignore the signal while it's got the mailbox locked. Reproduce code: --- Put this script in a file and run it with one argument, the name of a non-empty local mailbox, twice at the same time, e.g. (from bash) "php /tmp/imap_open.php /var/mail/jik & php /tmp/imap_open.php /var/mail/jik". It may not fail every time, but at least some of the times you do this, okne of the two php processes will print an error and exit because of the USR2 signal. -- Edit this bug report at http://bugs.php.net/?id=35894&edit=1
#35894 [Fbk->Opn]: php-imap doesn't trap USR2 when mailbox is locked
ID: 35894 User updated by: jik at kamens dot brookline dot ma dot us Reported By: jik at kamens dot brookline dot ma dot us -Status: Feedback +Status: Open Bug Type: IMAP related Operating System: Linux PHP Version: 5.1.1 New Comment: Woops, forgot the script. Here it is: You probably could have figured this out :-). You need an mbox file on which to run imap_open; there's no way to eliminate that dependency. Previous Comments: [2006-01-04 15:47:14] [EMAIL PROTECTED] Thank you for this bug report. To properly diagnose the problem, we need a short but complete example script to be able to reproduce this bug ourselves. A proper reproducing script starts with , is max. 10-20 lines long and does not require any external resources such as databases, etc. If possible, make the script source available online and provide an URL to it here. Try to avoid embedding huge scripts into the report. [2006-01-04 15:40:29] jik at kamens dot brookline dot ma dot us Description: The imap c-client has code in it to send a "kiss of death" SIGUSR2 to another process that has a mailbox locked, to cause that process to give up the lock if it no longer needs it. Anything which uses c-client is supposed to define a singla handler for SIGUSR2 to catch the signal and at minimum ignore it if the client doesn't want to relinquish the lock. If it doesn't do this, then the SIGUSR2 causes the process to die, and then the other process, which sent the signal, claims the lock. It appears that PHP's imap support doesn't define a SIGUSR2 handler, which means that if (a) imap_open is used to open a local file and (b) another process on the same machine happens to use c-client to open the same file at around the same time, the first process will die silently because of the SIGUSR2. To fix this, imap_open needs to define a SIGUSR2 handler to catch and ignore the signal while it's got the mailbox locked. Reproduce code: --- Put this script in a file and run it with one argument, the name of a non-empty local mailbox, twice at the same time, e.g. (from bash) "php /tmp/imap_open.php /var/mail/jik & php /tmp/imap_open.php /var/mail/jik". It may not fail every time, but at least some of the times you do this, okne of the two php processes will print an error and exit because of the USR2 signal. -- Edit this bug report at http://bugs.php.net/?id=35894&edit=1
