[libmicrohttpd] 100% CPU Usage with Keep-Alives

[Larry Wimble]

Greetings....

I am having a problem in my application which uses libmicrohttpd wherein 
the CPU usage spikes to 100% after the first request from Firefox and 
stays there until the connection times out or you close the browser.

I can reproduce this over and over.  I have:

1) Fired up my webserver based on libmicrohttpd
2) Fired up 'top' in another terminal.
3) Checked to see that CPU usage was normal (it is).
4) Made a request using CURL from the command line with no keep-alives.
5) Checked both netstat -an and top to make sure the connection was 
closed and CPU usage was normal.
6) Made a request from Firefox.
7) CPU Usage for my webserver process immediately spikes to 100% and 
stays there.
8) netstat -an states there is an established connection (as it should 
in a keep-alive situation)
9) Wait 60 seconds.  Process is still at 100%
9) Close browser (thus killing the connection).  CPU utilization 
immediately drops back to normal.

I temporarily added a "Connection: close" header to stop this which has 
been successful, however, since the application here is a web 
map-tile-server, the use of keep-alives is definitely desired.  I 
thought perhaps I had an errant thread or something, but have now 
verified that all calls to the callback specified in MHD_ start_daemon 
exit normally (with MHD_YES).  I am using no other threading.

Setup:

Gentoo Linux
libmicrohttpd 0.4.4
gcc 4.3.2
Not using SSL

My start-up code:

MHD_start_daemon(
              MHD_USE_THREAD_PER_CONNECTION, PORT, NULL, NULL,
              &http_request_handler, NULL, MHD_OPTION_END);

Any suggestions?

Larry

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