Date: Thu, 1 Apr 2004 11:28:12 -0800 (PST)
From: Davide Libenzi <davidel@xmailserver.org>
To: Ben Mansell <ben@zeus.com>
cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: epoll reporting events when it hasn't been asked to
In-Reply-To: <Pine.LNX.4.58.0404011909350.3066@stones.cam.zeus.com>
Message-ID: <Pine.LNX.4.44.0404011125510.2509-100000@bigblue.dev.mdolabs.com>
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On Thu, 1 Apr 2004, Ben Mansell wrote:

> > It is a feature. epoll OR user events with POLLHUP|POLLERR so that even if
> > the user sets the event mask to zero, it can still know when something
> > like those abnormal condition happened. Which problem do you see with this?
> 
> What should the application do if it gets events that it didn't ask for?
> If you choose to ignore them, the next time epoll_wait() is called it
> will return instantly with these same messages, so the app will spin and
> eat CPU.

Shouldn't the application handle those exceptional conditions instead of 
ignoring them?


> Perhaps it should only OR the user event with POLLHUP|POLLERR if
> POLLIN or POLLOUT is set?

This can certainly be done, since it's a one-liner fix. I'm not sure if it 
is the correct behaviour. Anyone else?


- Davide


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