From: Matthew Wilcox <willy@debian.org>
To: Grant Grundler <grundler@dsl2.external.hp.com>
Cc: Matthew Wilcox <willy@debian.org>, parisc-linux@parisc-linux.org
Subject: Re: [parisc-linux] atomic_t
Date: Mon, 14 Jan 2002 04:43:37 +0000 [thread overview]
Message-ID: <20020114044337.B9193@parcelfarce.linux.theplanet.co.uk> (raw)
In-Reply-To: <20020114040909.87321482A@dsl2.external.hp.com>; from grundler@dsl2.external.hp.com on Sun, Jan 13, 2002 at 09:09:09PM -0700
On Sun, Jan 13, 2002 at 09:09:09PM -0700, Grant Grundler wrote:
> You are only looking at interactions between atomic_set
> and atomic_add_return. Aren't there potentialially other
> types of interactions with other atomic operations?
> But I don't know. Alan Cox?
Not on PA... look at <asm/atomic.h>. There's only 3 primitives, all
other atomic ops are defined in terms of those.
> > Before step b leads to case 2. after step d leads to case 1. between
> > steps b and d, it's as if the atomic_set _never_happened_. It results
> > in v=4, a_a_r returns 4.
>
> I agree with the analysis.
>
> But someone thought it was time to reset the counter. And if
> it "never happened", then whoever is looking for 'v == 1' will
> never see it.
It's a race though; they can't guarantee to see it anyway.
> Even if that code doesn't exist today, it might exist in the future.
> I don't want to bet on corner cases with the semantics.
> Those types of bugs are hard to reproduce and hard to debug.
yeah, wasn't planning on committing.
--
Revolutions do not require corporate support.
next prev parent reply other threads:[~2002-01-14 4:43 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-01-13 21:15 [parisc-linux] atomic_t Matthew Wilcox
2002-01-14 4:09 ` Grant Grundler
2002-01-14 4:43 ` Matthew Wilcox [this message]
2002-01-14 7:12 ` Grant Grundler
2002-01-14 9:54 ` Alan Cox
-- strict thread matches above, loose matches on Subject: below --
2002-01-14 6:54 John Marvin
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