lkml.org 
[lkml]   [2007]   [Aug]   [16]   [last100]   RSS Feed
Views: [more markup]  [less markup]  [headers]  [forward] 
 
Messages in this thread
/
DateThu, 16 Aug 2007 15:48:54 -0400
FromChris Snook <>
SubjectRe: [PATCH 0/24] make atomic_read() behave consistently across all architectures
Herbert Xu wrote:
> On Thu, Aug 16, 2007 at 10:06:31AM +0200, Stefan Richter wrote:
>>> Do you (or anyone else for that matter) have an example of this?>> The only code I somewhat know, the ieee1394 subsystem, was perhaps
>> authored and is currently maintained with the expectation that each
>> occurrence of atomic_read actually results in a load operation, i.e. is
>> not optimized away.  This means all atomic_t (bus generation, packet and
>> buffer refcounts, and some other state variables)* and likewise all
>> atomic bitops in that subsystem.> > Can you find an actual atomic_read code snippet there that is
> broken without the volatile modifier?

A whole bunch of atomic_read uses will be broken without the volatile 
modifier once we start removing barriers that aren't needed if volatile 
behavior is guaranteed.

barrier() clobbers all your registers.  volatile atomic_read() only 
clobbers one register, and more often than not it's a register you 
wanted to clobber anyway.

	-- Chris
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-08-16 22:27    [from the cache]
©2003-2008