[tor-bugs] #5263 [Tor Relay]: Busy/infinite Libevent loops

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#5263: Busy/infinite Libevent loops
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 Reporter:  robgjansen  |          Owner:                    
     Type:  defect      |         Status:  needs_review      
 Priority:  major       |      Milestone:  Tor: 0.2.2.x-final
Component:  Tor Relay   |        Version:                    
 Keywords:              |         Parent:                    
   Points:              |   Actualpoints:                    
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Changes (by robgjansen):

 * cc: jansen@… (added)


Comment:

 > >The reason that both read and write events are both de-registered when
 the marked connection can not flush is because both result in the same
 behavior. Both read/write events on marked connections will never again do
 any actual reads/writes, and are only useful to trigger the flush and
 close the connection.
 >
 > I think I agree with this patch except for this question.  Is it really
 the case that we reach this point with the connection still reading?  Keep
 in mind that this case can only happen if the connection is marked and is
 busy flushing; a connection in that condition *shouldn't* be reading.
 Did you run into some that were? If I missed something, though: sz==0 in
 that case doesn't mean that read is blocked on bandwidth; no read was
 attempted in the code above, and the read bucket wasn't examined.
 >
 > Can you tell me more about the read case here?

 I did run into a case where a connection was reading.

 You are technically correct about sz==0 not implying read is blocked on
 bandwidth. The reason I added that was to catch reading connections that
 are flushing but not registered as writing, because we need a way for the
 event to later get activated, flushed, and removed. Would it be better to
 remove the read event and set write_blocked_on_bandwidth to get ensure
 removal later?

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/5263#comment:4>
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