> On Nov. 18, 2014, 1:25 p.m., Matt Jordan wrote: > > From http://www.washington.edu/imap/documentation/internal.txt.html: > > > > {quote} > > * * * IMPORTANT * * * > > > > Any multi-threaded application should test stream->lock prior to > > calling any c-client stream functions. Any attempt to call a > > mail_xxx() function while one is already in progress on the same > > stream will cause the application to fail in unpredictable ways. > > > > Note that this check is insufficient in a preemptive-scheduling > > multi-tasking application due to the possibility of a timing race. > > Such applications must be written so that only one process accesses > > the stream, or to have a higher level lock. > > > > Since MAIL operations will not finish until they are completed, a > > single-tasking application does not have to worry about this problem, > > except in the callback invoked from MAIL (e.g. mm_exists(), etc.) in which > > case the stream is *always* locked. > > {quote} > > > > So, a few things from this: > > (1) Based on the description from the UW IMAP documentation, locking > > vms->lock is sufficient *if* other mail accesses also lock the same vms > > object for that stream. If that isn't happening, then your patch probably > > won't fix anything, since both mail_open calls were already protected by > > the vms->lock and your global lock doesn't protect any other mail_XXXX > > accesses. The only way your patch would affect anything is if there were > > two different vms objects being used to open the same stream at the same > > time. > > (2) Your backtrace on the issue doesn't show concurrent accesses to > > vm_execmain - although a lot of symbols are missing - so right now it's > > impossible to tell who the offending accesses are. It's also impossible to > > know if it is due to two concurrent accesses of mail_open with different > > vms objects, or something else. > > > > Generally, I'm not this patch fixes your issue.
The concern we found was that some code called by mail_open uses static variables, specifically the ip_nametoaddr function - at least the ip6_unix.c implementation of it, which is where we're seeing crashes. We believe the problem may be 2 DIFFERENT streams are being opened at once, correctly locked individually, but ultimately causing a conflict with a static variable deep inside the uw-imap code. - Ben ----------------------------------------------------------- This is an automatically generated e-mail. To reply, visit: https://reviewboard.asterisk.org/r/4188/#review13790 ----------------------------------------------------------- On Nov. 17, 2014, 3:03 p.m., David Duncan Ross Palmer wrote: > > ----------------------------------------------------------- > This is an automatically generated e-mail. To reply, visit: > https://reviewboard.asterisk.org/r/4188/ > ----------------------------------------------------------- > > (Updated Nov. 17, 2014, 3:03 p.m.) > > > Review request for Asterisk Developers. > > > Bugs: ASTERISK-24516 > https://issues.asterisk.org/jira/browse/ASTERISK-24516 > > > Repository: Asterisk > > > Description > ------- > > Asterisk segfaults when playing back voicemail under high concurrency with an > IMAP backend > > > Diffs > ----- > > /trunk/apps/app_voicemail.c 427675 > > Diff: https://reviewboard.asterisk.org/r/4188/diff/ > > > Testing > ------- > > Rapid load testing performed with {{SIPp}}: > {code} > sipp -sn uac -d 7000 -s ‘*1’ 127.0.0.1 -l 400 -mp 5606 > {code} > > > Thanks, > > David Duncan Ross Palmer > >
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