[users@httpd] error in mod_proxy?

[xiang dong <thincat.china@xxxxxxxxx>]

hi, 

I use module mod_proxy of apache 2.0.54 as reverse proxy for cgi servers.
Sometimes I saw error messages in error_log which were 
"proxy: error reading status line from remote server"
"proxy: Error reading from remote server returned by".

And the proxy return corresponding 502 http status  to client. When I check the back end
cgi servers, I found that the cgi servers return 200 http status to the proxy.

Would you tell me what problem it may be , and what situation do these errors occur?

thank you very much.

Looking forward to your reply.
Best Regards,