[Varnish] #644: Deadlock in 2.0.x under high load.

[Varnish]

#644: Deadlock in 2.0.x under high load.
----------------------+-----------------------------------------------------
 Reporter:  kmcfate   |        Owner:  phk
     Type:  defect    |       Status:  new
 Priority:  normal    |    Milestone:     
Component:  varnishd  |      Version:  2.0
 Severity:  normal    |   Resolution:     
 Keywords:  deadlock  |  
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Comment (by phk):

 We have seen this reported before, and have at present no handle on it.

 I will not rule out a bug in Varnish, but given the symptoms, as described
 by you and others, a kernel bug starts to sound plausible.

 If you can (or happen to) reproduce it, it would be valuable information
 to know if the waiter thread is stuck in epoll_wait, not coming back at
 all, if it comes back on the timer, or if it busy-spins calling epoll_wait
 all the time, getting nothing done.

 If it is feasible with your system load, try running with the "poll"
 waiter, and see if that also suffers from the same problem (which would
 indicate kernel/pipe issue).

 Poul-Henning

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Ticket URL: <http://www.varnish-cache.org/ticket/644#comment:1>
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