lkml.org 
[lkml]   [2016]   [Feb]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 1/3] tools/liblockdep: add userspace version of READ_ONCE
From
Date
On 02/11/2016 10:16 AM, Peter Zijlstra wrote:
> On Thu, Feb 11, 2016 at 12:33:30AM +0100, Alfredo Alvarez Fernandez wrote:
>> From: Alfredo Alvarez Fernandez <alfredoalvarezfernandez@gmail.com>
>>
>> This was added to the kernel code in 1658d35ead5d ("list: Use
>> READ_ONCE() when testing for empty lists")
>> There's nothing special we need to do about it in userspace.
>>
>> Signed-off-by: Alfredo Alvarez Fernandez <alfredoalvarezfernandez@gmail.com>
>> ---
>> tools/lib/lockdep/uinclude/linux/compiler.h | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff --git a/tools/lib/lockdep/uinclude/linux/compiler.h b/tools/lib/lockdep/uinclude/linux/compiler.h
>> index 6386dc3..fd3e56a 100644
>> --- a/tools/lib/lockdep/uinclude/linux/compiler.h
>> +++ b/tools/lib/lockdep/uinclude/linux/compiler.h
>> @@ -3,6 +3,7 @@
>>
>> #define __used __attribute__((__unused__))
>> #define unlikely
>> +#define READ_ONCE(x) (x)
>> #define WRITE_ONCE(x, val) x=(val)
>
> I would argue we'd still very much want the volatile cast for both READ
> and WRITE_ONCE().
>
> Why do these things have different semantics between user and kernel
> space?

You're right. I'll send a patch.


Thanks,
Sasha

\
 
 \ /
  Last update: 2016-02-16 19:41    [W:0.135 / U:2.624 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site