[Buildbot-commits] [Buildbot] #2055: buildmaster spins when build starts

[Buildbot]

#2055: buildmaster spins when build starts
-----------------------+----------------------
Reporter:  mmorse      |       Owner:
    Type:  defect      |      Status:  new
Priority:  major       |   Milestone:  ongoing
 Version:  0.8.4p2     |  Resolution:
Keywords:  threadbugs  |
-----------------------+----------------------
Changes (by dustin):

 * keywords:  performance => threadbugs
 * milestone:  0.8.5 => ongoing


Comment:

 Another possibility here is that this is related to problems with Python's
 thread-safety on the mac.  We've seen deadlocks because pthreads mutexes
 are not re-entrant (suspected in #1992).  There seem to be circumstances
 in which massive numbers of signals are delivered to the buildmaster -
 possibly related to being run in the background?

 In this case, it looks like there are two concurrent calls to perror, both
 spinning on a semaphore of some sort.

 As far as I can tell, this is due to a bogus implementation of pthreads in
 OpenBSD -- for some reason the BSD's never really got entirely onboard
 with multi-threaded programming -- and OS X has inherited that
 implementation.  Newer versions of Python seem to have the worst time with
 it, although I'm not sure what changes have been at fault there.

 At any rate, this isn't a Buildbot bug, beyond the fact that Buildbot
 makes heavier use of threads in 0.8.4 and above, so there's not much to do
 here.  I'm going to move this to the "ongoing" milestone and add a
 keyword, in case further clarity comes at some point in the future and we
 can make some clear recommendations to users.

-- 
Ticket URL: <http://trac.buildbot.net/ticket/2055#comment:8>
Buildbot <http://buildbot.net/>
Buildbot: build/test automation