lkml.org 
[lkml]   [2014]   [Jan]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v8 4/4] qrwlock: Use smp_store_release() in write_unlock()
On Tue, Jan 14, 2014 at 10:01:04AM -0800, Richard Henderson wrote:
> On 01/14/2014 09:08 AM, Matt Turner wrote:
> > On Tue, Jan 14, 2014 at 3:03 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> >> On Tue, Jan 14, 2014 at 10:28:23AM +0800, Daniel J Blueman wrote:
> >>>> Peter,
> >>>>
> >>>> I found out that the build failure was caused by the fact that the
> >>>> __native_word() macro (used internally by compiletime_assert_atomic())
> >>>> allows only a size of 4 or 8 for x86-64. The data type that I used is a
> >>>> byte. Is there a reason why byte and short are not considered native?
> >>>
> >>> It seems likely it was implemented like that since there was no existing
> >>> need; long can be relied on as the largest native type, so this should
> >>> suffice and works here:
> >>
> >> There's Alphas that cannot actually atomically adres a byte; I do not
> >> konw if Linux cares about them, but if it does, we cannot in fact rely
> >> on this in generic primitives like this.
> >
> > That's right, and thanks for the heads-up. Alpha can only address 4
> > and 8 bytes atomically. (LDL_L, LDQ_L, STL_C, STQ_C).
> >
> > The Byte-Word extension in EV56 doesn't add new atomics, so in fact no
> > Alphas can address < 4 bytes atomically.
>
> Emulated with aligned 4 byte atomics, and masking. The same is true for arm,
> ppc, mips which, depending on cpu, also lack < 4 byte atomics.

Which means that Alpha should be able to similarly emulate 1-byte and
2-byte atomics, correct?

Thanx, Paul



\
 
 \ /
  Last update: 2014-01-15 01:21    [W:0.102 / U:0.776 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site