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Date: Tue, 04 Dec 2001 16:53:42 -0500
From: Nathan Bryant <nbryant@optonline.net>
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To: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
CC: Doug Ledford <dledford@redhat.com>, Mario Mikocevic <mozgy@hinet.hr>
Subject: Re: i810 audio patch
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ok, i'm learning here ;)

it seems i guessed wrong, and schedule() wakes up on a wait queue which 
has been added by poll_wait; poll_wait doesn't actually do any sleeping 
so no loop is necessary in i810_poll; it will be called again by do_poll 
or do_select after the call to schedule. so no latency and no problem.

right?

Nathan Bryant wrote:

> fs/select.c:do_poll() calls schedule_timeout() after all do_pollfd's 
> have returned empty sets and there is still time remaining. so if you 
> just eliminate the loop in i810_poll, it will loop back and if there's 
> data available, poll(2) would return properly, but with extra latency. 
> i assume sys_select behaves the same way...
>
> so, 2 choices to eliminate latency, either hack i810_poll further, or 
> be a lot more intelligent about calling wake_up. am i wrong?
>



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