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Date: Tue, 4 Mar 2008 04:16:33 +1100
From: Nick Piggin <nickpiggin@...oo.com.au>
To: Alan Cox <alan@...rguk.ukuu.org.uk>
Cc: Alan Stern <stern@...land.harvard.edu>,
Pavel Machek <pavel@....cz>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Andrew Morton <akpm@...l.org>,
Zdenek Kabelac <zdenek.kabelac@...il.com>, davem@...emloft.net,
"Rafael J. Wysocki" <rjw@...k.pl>,
Pierre Ossman <drzeus-mmc@...eus.cx>,
Kernel development list <linux-kernel@...r.kernel.org>,
pm list <linux-pm@...ts.linux-foundation.org>
Subject: Re: [patch] Re: using long instead of atomic_t when only set/read is required
On Tuesday 04 March 2008 02:53, Alan Cox wrote:
> > Atomicity of reads of write for pointers and integral types (other than
> > long long) should be documented.
>
> NAK.
>
> Atomicity of reads or writes for pointers and integral types is NOT
> guaranteed. Gcc doesn't believe in your guarantee.
Are you sure gcc doesn't? Or is it just "C"?
Linux wouldn't work today if gcc did something non-atomic there
(presuming you're talking about naturally aligned pointers/ints).
It is widely used and accepted.
RCU users are far from the only places to rely on this, although
I guess they are the main ones when it comes to assigning pointers
atomically.
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