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Message-ID: <598a055d0602281236m7eac9c09oc60af9ce28e7e4bf@mail.gmail.com>
Date: Tue, 28 Feb 2006 15:36:11 -0500
From: "Li, Peng" <ringer9cs@gmail.com>
To: "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>
Subject: Thread safety for epoll/libaio
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I apologize if I should not post this on LKML, but there seems to be
some lack of documentation for using epoll/AIO with threads.  Are
these interfaces thread-safe?  Can I use them safely in the following
way:

Thread A:  while(1) { io_getevents();  ... }
// wait forever until an event occurs, then handles the event and loop

Thread B:  while(1) { epoll_wait();  ... }
// same as thread A

Thread C:  ... io_submit(); ...

Thread D:  ... epoll_ctl(); ....

Suppose thread B calls epoll_wait and blocks before thread D calls
epoll_ctl.  Is it safe to do so? Will thread B be notified for the
event submitted by thread D?  Thread A and C pose the same question
for AIO.

I wrote a simple program to test these interfaces and they seem to
work without problems, but I am not sure if it is really safe to do so
in general.  If all of them works, it seems easy to use epoll and AIO
together as I can simply use another thread to harvest events from
thread A and B and make it look like a unified event notification
interface.

Peng
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