From: "David Schwartz" <davids@webmaster.com>
To: "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>
Subject: RE: Thread safety for epoll/libaio
Date: Tue, 28 Feb 2006 19:48:46 -0800
Message-ID: <MDEHLPKNGKAHNMBLJOLKMEAIKHAB.davids@webmaster.com>
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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:

	They are thread safe.

> 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.

	Using the interfaces this way is pretty much their entire point. They'd be
almost useless if you couldn't use them in this way.

	DS


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