linux-kernel - Re: disappearing listen()ed SO_REUSEPORT sockets across fork() when using epoll

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Message-ID: <52939151.8030908@akamai.com>
Date:	Mon, 25 Nov 2013 13:05:05 -0500
From:	Jason Baron <jbaron@...mai.com>
To:	Shawn Landden <shawnlandden@...il.com>
CC:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Tom Herbert <therbert@...gle.com>
Subject: Re: disappearing listen()ed SO_REUSEPORT sockets across fork() when
 using epoll

On 11/22/2013 12:53 PM, Shawn Landden wrote:
> Hello, when running the attached program on 3.12 child processes
> are missing a socket fd opened, set with SO_REUSEPORT, listen()ed to,
> and added to epoll_ctl().
> 
> This is the output I get when pointing "wget http://localhost:5555/"
> at the attached program:
> 
> main PID 31591
> PID 31634 started
> PID 31634 accept()ed connection
> PID 31635 started
> PID 31636 started
> PID 31635 accept() failed: Bad file descriptor
> PID 31636 accept() failed: Bad file descriptor
> PID 31634 accept()ed connection
> PID 31634 accept()ed connection
> PID 31634 accept()ed connection
> PID 31634 accept()ed connection
> 
> 
> While I would expect something like:
> 
> main PID 31591
> PID 31634 started
> PID 31634 accept()ed connection
> PID 31635 started
> PID 31636 started
> PID 31635 accept()ed connection
> PID 31636 accept()ed connection
> 
> -more new processes, but inversely proportional to number of listening processes
> -accept() always returns successfully
> 
> 

The 'close(sockfd);' looks to be racing with the accept() calls. Removing seems
to get the result you are looking for.

Thanks,

-Jason

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