lkml.org 
[lkml]   [2012]   [Aug]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [ 20/82] ARM: 7467/1: mutex: use generic xchg-based implementation for ARMv6+
From
Date
On Mon, 2012-08-13 at 13:18 -0700, Greg Kroah-Hartman wrote:
> From: Greg KH <gregkh@linuxfoundation.org>
>
> 3.5-stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Will Deacon <will.deacon@arm.com>
>
> commit a76d7bd96d65fa5119adba97e1b58d95f2e78829 upstream.
>
> The open-coded mutex implementation for ARMv6+ cores suffers from a
> severe lack of barriers, so in the uncontended case we don't actually
> protect any accesses performed during the critical section.
>
> Furthermore, the code is largely a duplication of the ARMv6+ atomic_dec
> code but optimised to remove a branch instruction, as the mutex fastpath
> was previously inlined. Now that this is executed out-of-line, we can
> reuse the atomic access code for the locking (in fact, we use the xchg
> code as this produces shorter critical sections).
>
> This patch uses the generic xchg based implementation for mutexes on
> ARMv6+, which introduces barriers to the lock/unlock operations and also
> has the benefit of removing a fair amount of inline assembly code.
[...]

Here also, I think this should be deferred.

Ben.

--
Ben Hutchings
I say we take off; nuke the site from orbit. It's the only way to be sure.
[unhandled content-type:application/pgp-signature]
\
 
 \ /
  Last update: 2012-08-15 16:43    [W:0.686 / U:0.180 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site