Re: [Libevent-users] 100% cpu utilization with openssl bufferevent.

[Sebastian Sjöberg <Sebastian.Sjoberg@xxxxxxxx>]

On May 18, 2010, at 9:33 PM, Nick Mathewson wrote:

> On Thu, Apr 29, 2010 at 2:14 PM, Sebastian Sjöberg
> <Sebastian.Sjoberg@xxxxxxxx> wrote:
> [...]
>>> If it's the second problem, I'd start by testing whether stuff begins
>>> to work when you set the EVENT_NOEPOLL environment variable.  If so,
>>> then the bug is probably with the epoll backend -- or at least, it
>>> requires the epoll backend to appear.  To debug this, I'd add
>>> debugging messages to the loop in epoll_dispatch that calls
>>> evmap_io_active to tell me whenever it decided not to call
>>> evmap_io_active, and I'd have evmap_io_active tell me whenever it made
>>> 0 events become active.
>> 
>> Cheers, I haven't yet been able to reproduce it when disabling epoll.
>> 
>> I've started to debug the evmap_io_active calls and after a while there are a no events being activated as you said so I guess at some point the there's a mismatch between what's in epoll and in the event map.
> 
> Hi, Sebastian!  Have you had any luck tracking this down?  I'd really
> like to try to get this bug fixed before 2.0 goes into a release
> candidate status.

Hi Nick,

No luck so far, I had to stop looking for the issue.

> 
> I've looked through the code, and tried to reproduce the behavior
> you're seeing, but I haven't been able to figure out where the trouble
> is.  I'm attaching a patch that should give a warning assertion
> failure when the error condition hits; together with debugging log
> output [build libevent with -DDEBUG to get that ], it might be enough
> to track the bug down.

I will try the patch later today and let you know.

> 
> Also, is there some code I can run to try to reproduce this bug
> myself?  I've tried writing examples with openssl, but I can't make
> the warnings trigger.

I tried to create a minimal example but couldn't reproduce the issue but I try again.

Best regards,
Sebastian Sjoberg

> 
> yrs,
> -- 
> Nick
> <0001-Warning-statements-to-catch-possible-bug-in-epoll.patch>

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