From: Arnd Bergmann <arnd@arndb.de>
To: David Howells <dhowells@redhat.com>
Cc: linux-arch@vger.kernel.org, x86@kernel.org, will.deacon@arm.com,
linux-kernel@vger.kernel.org, ramana.radhakrishnan@arm.com,
paulmck@linux.vnet.ibm.com, dwmw2@infradead.org
Subject: Re: [RFC PATCH 01/15] cmpxchg_local() is not signed-value safe, so fix generic atomics
Date: Wed, 18 May 2016 17:29:49 +0200 [thread overview]
Message-ID: <3591761.rzLMs6OGtT@wuerfel> (raw)
In-Reply-To: <146358424513.8596.16888168996359637266.stgit@warthog.procyon.org.uk>
On Wednesday 18 May 2016 16:10:45 David Howells wrote:
> cmpxchg_local() is not signed-value safe because on a 64-bit machine signed
> int arguments to it may be sign-extended to signed long _before_ begin cast
> to unsigned long. This potentially causes comparisons to fail when dealing
> with negative values.
>
> Fix the generic atomic functions that are implemented in terms of cmpxchg()
> to cast their arguments to unsigned int before calling cmpxchg().
>
> Signed-off-by: David Howells <dhowells@redhat.com>
>
Isn't the problem you describe something that cmpxchg() could prevent instead?
Arnd
next prev parent reply other threads:[~2016-05-18 15:30 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-18 15:10 [RFC PATCH 00/15] Provide atomics and bitops implemented with ISO C++11 atomics David Howells
2016-05-18 15:10 ` [RFC PATCH 01/15] cmpxchg_local() is not signed-value safe, so fix generic atomics David Howells
2016-05-18 15:10 ` David Howells
2016-05-18 15:29 ` Arnd Bergmann [this message]
2016-05-18 15:10 ` [RFC PATCH 02/15] tty: ldsem_cmpxchg() should use cmpxchg() not atomic_long_cmpxchg() David Howells
2016-05-18 15:10 ` [RFC PATCH 03/15] Provide atomic_t functions implemented with ISO-C++11 atomics David Howells
2016-05-18 15:10 ` David Howells
2016-05-18 17:31 ` Peter Zijlstra
2016-05-18 17:32 ` Peter Zijlstra
2016-05-18 17:32 ` Peter Zijlstra
2016-05-19 7:36 ` David Woodhouse
2016-05-19 7:45 ` Peter Zijlstra
2016-05-18 17:33 ` Peter Zijlstra
2016-05-19 9:52 ` David Howells
2016-05-19 10:50 ` Peter Zijlstra
2016-05-19 11:31 ` Peter Zijlstra
2016-05-19 11:33 ` Peter Zijlstra
2016-05-19 14:22 ` Paul E. McKenney
2016-05-19 14:41 ` Peter Zijlstra
2016-05-19 15:00 ` Paul E. McKenney
2016-05-20 9:32 ` Michael Ellerman
2016-05-20 9:32 ` Michael Ellerman
2016-05-23 18:39 ` Paul E. McKenney
2016-06-01 14:16 ` Will Deacon
2016-06-01 14:16 ` Will Deacon
2016-05-18 15:11 ` [RFC PATCH 04/15] Convert 32-bit ISO atomics into a template David Howells
2016-05-18 15:11 ` David Howells
2016-05-18 15:11 ` [RFC PATCH 05/15] Provide atomic64_t and atomic_long_t using ISO atomics David Howells
2016-05-18 15:11 ` David Howells
2016-05-18 15:11 ` [RFC PATCH 06/15] Provide 16-bit " David Howells
2016-05-18 15:11 ` David Howells
2016-05-18 17:28 ` Peter Zijlstra
2016-05-18 15:11 ` [RFC PATCH 07/15] Provide cmpxchg(), xchg(), xadd() and __add() based on ISO C++11 intrinsics David Howells
2016-05-18 15:11 ` David Howells
2016-05-18 15:11 ` [RFC PATCH 08/15] Provide an implementation of bitops using C++11 atomics David Howells
2016-05-18 15:11 ` David Howells
2016-05-18 15:11 ` [RFC PATCH 09/15] Make the ISO bitops use 32-bit values internally David Howells
2016-05-18 15:11 ` David Howells
2016-05-18 15:11 ` [RFC PATCH 10/15] x86: Use ISO atomics David Howells
2016-05-18 15:12 ` [RFC PATCH 11/15] x86: Use ISO bitops David Howells
2016-05-18 15:12 ` David Howells
2016-05-18 15:12 ` [RFC PATCH 12/15] x86: Use ISO xchg(), cmpxchg() and friends David Howells
2016-05-18 15:12 ` David Howells
2016-05-18 15:12 ` [RFC PATCH 13/15] x86: Improve spinlocks using ISO C++11 intrinsic atomics David Howells
2016-05-18 15:12 ` David Howells
2016-05-18 17:37 ` Peter Zijlstra
2016-05-18 15:12 ` [RFC PATCH 14/15] x86: Make the mutex implementation use ISO atomic ops David Howells
2016-05-18 15:12 ` David Howells
2016-05-18 15:12 ` [RFC PATCH 15/15] x86: Fix misc cmpxchg() and atomic_cmpxchg() calls to use try/return variants David Howells
2016-05-18 15:12 ` David Howells
2016-05-18 17:22 ` [RFC PATCH 00/15] Provide atomics and bitops implemented with ISO C++11 atomics Peter Zijlstra
2016-05-18 17:45 ` Peter Zijlstra
2016-05-18 18:05 ` Peter Zijlstra
2016-05-19 0:23 ` Paul E. McKenney
2016-06-01 14:45 ` Will Deacon
2016-06-01 14:45 ` Will Deacon
2016-06-08 20:01 ` Paul E. McKenney
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