From: Roland Dreier <roland@topspin.com>
To: root@chaos.analogic.com
Cc: Linux kernel <linux-kernel@vger.kernel.org>
Subject: Re: poll() in 2.6 and beyond
Date: 02 Mar 2004 12:04:43 -0800 [thread overview]
Message-ID: <527jy3qalg.fsf@topspin.com> (raw)
In-Reply-To: <Pine.LNX.4.53.0403021318580.796@chaos>
Richard> Poll in 2.6.0; when a driver routine calls poll_wait() it
Richard> returns <<immediately>> to somewhere in the kernel, then
Richard> waits for my wake_up_interuptible(), before returning
Richard> control to a user sleeping in poll(). This means that the
Richard> user gets the wrong poll return value! It doesn't get the
Richard> value it was given as a result of the interrupt, but the
Richard> value that existed (0) before the interrupt occurred.
Nothing has changed in 2.6 that I know of. poll_wait() always
returned immediately to the driver. The driver's poll method is
supposed to call poll_wait() on the wait queues that indicate a change
in poll status, and then return with the current status.
Read the description of "poll and select" in LDD:
<http://www.xml.com/ldd/chapter/book/ch05.html#t3>
- Roland
next prev parent reply other threads:[~2004-03-02 20:04 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-03-02 18:21 poll() in 2.6 and beyond Richard B. Johnson
2004-03-02 20:04 ` Roland Dreier [this message]
2004-03-02 20:24 ` Richard B. Johnson
2004-03-02 21:00 ` Roland Dreier
2004-03-02 21:26 ` Richard B. Johnson
2004-03-02 21:39 ` Roland Dreier
2004-03-02 21:59 ` Richard B. Johnson
2004-03-02 22:41 ` Dave Dillow
2004-03-02 22:56 ` Roland Dreier
2004-03-02 23:16 ` Richard B. Johnson
2004-03-02 23:21 ` Roland Dreier
[not found] <1vmPm-4lU-11@gated-at.bofh.it>
[not found] ` <1vonq-6dr-37@gated-at.bofh.it>
[not found] ` <1voGY-6vC-41@gated-at.bofh.it>
[not found] ` <1vpjt-7dl-17@gated-at.bofh.it>
[not found] ` <1vpCV-7wY-41@gated-at.bofh.it>
[not found] ` <1vpWa-7Py-19@gated-at.bofh.it>
2004-03-02 22:53 ` Bill Davidsen
2004-03-02 22:57 ` Roland Dreier
2004-03-02 23:32 ` Richard B. Johnson
2004-03-03 0:07 ` John Muir
2004-03-03 1:18 ` Richard B. Johnson
2004-03-03 4:04 ` Roland Dreier
2004-03-03 12:38 ` Richard B. Johnson
2004-03-03 14:29 ` Davide Libenzi
2004-03-03 3:57 ` David Dillow
2004-03-03 18:23 ` Richard B. Johnson
2004-03-03 19:29 ` Dave Dillow
2004-03-03 20:10 ` Richard B. Johnson
2004-03-03 22:25 ` Linus Torvalds
2004-03-03 22:42 ` Richard B. Johnson
2004-03-03 23:14 ` Linus Torvalds
2004-03-03 22:52 ` Linus Torvalds
2004-03-03 23:07 ` Richard B. Johnson
-- strict thread matches above, loose matches on Subject: below --
2004-03-03 3:06 linux
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