From: Linus Torvalds <torvalds@osdl.org>
To: "Richard B. Johnson" <root@chaos.analogic.com>
Cc: David Dillow <dave@thedillows.org>,
Bill Davidsen <davidsen@tmr.com>,
Roland Dreier <roland@topspin.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: poll() in 2.6 and beyond
Date: Wed, 3 Mar 2004 14:52:54 -0800 (PST) [thread overview]
Message-ID: <Pine.LNX.4.58.0403031442580.3000@ppc970.osdl.org> (raw)
In-Reply-To: <Pine.LNX.4.58.0403031419280.3000@ppc970.osdl.org>
On Wed, 3 Mar 2004, Linus Torvalds wrote:
>
> You should clear the "events pending" flag only when you literally remove
> the event (ie at "read()" time, not at "poll()" time). Because the
> select() code _will_ call down to the "poll()" functions multiple times if
> it gets woken up for any bogus reason.
Hmm.. The above is all still true and your poll() implementation is bad,
but looking at your test program, the problematic case really shouldn't
trigger (we should call poll() multiple times only when it returns zero).
To trigger that bug, you'd have to occasionally call poll() with the
POLLIN bit clear in the incoming events, which your test program doesn't
ever do.
Anyway, you should move the clearing to read(), but there may well be
something else going on too.
What's the frequency you are programming the thing to send interrupts at?
Linus
next prev parent reply other threads:[~2004-03-03 22:46 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
[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 [this message]
2004-03-03 23:07 ` Richard B. Johnson
2004-03-03 3:06 linux
-- strict thread matches above, loose matches on Subject: below --
2004-03-02 18:21 Richard B. Johnson
2004-03-02 20:04 ` Roland Dreier
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
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