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http://nagoya.apache.org/bugzilla/show_bug.cgi?id=20695 deadlock when mod_proxy used with mod_ext_filter Summary: deadlock when mod_proxy used with mod_ext_filter Product: Apache httpd-2.0 Version: 2.0.46 Platform: PC OS/Version: Windows XP Status: NEW Severity: Major Priority: Other Component: mod_ext_filter AssignedTo: bugs@httpd.apache.org ReportedBy: [EMAIL PROTECTED] If you set up Apache to filter mod_proxy output using mod_ext_filter then an Apache thread and the filter process will deadlock in the cases where the proxied http response exceed one bucket. This occurs on the Windows NT/2K/XP platform. I did not test the behavior on other platforms. The deadlock occurs because: mod_proxy's ap_proxy_http_process_response calls ap_pass_brigade which calls mod_ext_filter's ef_output_filter which calls apr_file_read which blocks on WaitForSingleObject(.., INFINITE) because the pipe timeout is set to minus 1. At this point Apache is waiting for the filter process to produce output but the filter process is waiting for Apache's ap_proxy_http_process_response to resume and provide more input. Deadlock! It appears that this problem can be solved by setting the timeout on the filter process's stdout to zero. Immediately after the apr_proc_create() call in init_ext_filter_process() I put the following: /* don't block on reading from child's stdout */ rc = apr_file_pipe_timeout_set(ctx->proc->out, 0); ap_assert(rc == APR_SUCCESS); and it eliminated the deadlock because then apr_file_read will return APR_STATUS_IS_EAGAIN when there is no more output from the filter process rather than blocking. I'm not familiar enough to know whether this problem affects other platforms or whether this suggested fix will adversely affect other platforms. I hope this helps! --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
