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

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Date:	Fri, 22 Nov 2013 09:53:52 -0800
From:	Shawn Landden <shawnlandden@...il.com>
To:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Tom Herbert <therbert@...gle.com>
Subject: disappearing listen()ed SO_REUSEPORT sockets across fork() when using epoll

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


-- 

---
Shawn Landden
+1 360 389 3001 (SMS preferred)

View attachment "epoll_test.c" of type "text/x-csrc" (2538 bytes)