On Thu, Dec 04, 2014 at 09:45:46PM +, One Thousand Gnomes wrote:
> > anywhere in that translation unit. After all, any non-static function
> > in that translation unit might be called from some other translation
> > unit that -did- use locking or whatever.
> >
> > I will let you know how it g
> anywhere in that translation unit. After all, any non-static function
> in that translation unit might be called from some other translation
> unit that -did- use locking or whatever.
>
> I will let you know how it goes. ;-)
It breaks DEC10 ;-)
If there is kickback over things like optimisat
On Thu, Dec 04, 2014 at 12:00:52PM -0800, Paul E. McKenney wrote:
[ . . . ]
> So any compiler that clobbers some adjacent non-bitfield variable or
> field that is accessible by other threads is not just despicable, it
> fails to conform to the standard.
>
> Whew! ;-)
And part of the reason for
On Thu, Dec 04, 2014 at 11:18:17AM -0800, Linus Torvalds wrote:
> On Thu, Dec 4, 2014 at 10:36 AM, Paul E. McKenney
> wrote:
> >
> > I have to ask... Does this mean we can remove the current
> > restrictions against 8-bit and 16-bit access from smp_load_acquire()
> > and smp_store_release()?
>
>
On Thu, Dec 4, 2014 at 10:36 AM, Paul E. McKenney
wrote:
>
> I have to ask... Does this mean we can remove the current
> restrictions against 8-bit and 16-bit access from smp_load_acquire()
> and smp_store_release()?
I'd certainly be ok with it. Alpha doesn't have acquire/release
semantics anywa
On Thu, Dec 04, 2014 at 10:02:14AM -0800, Linus Torvalds wrote:
> On Wed, Dec 3, 2014 at 11:02 PM, Paul E. McKenney
> wrote:
> > On Wed, Dec 03, 2014 at 10:40:45PM -0800, Linus Torvalds wrote:
> >> On Dec 3, 2014 10:31 PM, "Linus Torvalds"
> >> wrote:
> >> >
> >> > So no, no, no. C got this wrong
On Wed, Dec 3, 2014 at 11:02 PM, Paul E. McKenney
wrote:
> On Wed, Dec 03, 2014 at 10:40:45PM -0800, Linus Torvalds wrote:
>> On Dec 3, 2014 10:31 PM, "Linus Torvalds"
>> wrote:
>> >
>> > So no, no, no. C got this wrong. Volatile data structures are a
>> fundamental mistake and a bug.
>>
>> BTW,
On Wed, Dec 03, 2014 at 10:40:45PM -0800, Linus Torvalds wrote:
> On Dec 3, 2014 10:31 PM, "Linus Torvalds"
> wrote:
> >
> > So no, no, no. C got this wrong. Volatile data structures are a
> fundamental mistake and a bug.
>
> BTW, I'm not at all interested in language lawyering and people who say
One point of the patch is "one more thing to watch for" in generated code,
namely temporary clobbering of synchronization variables, locks included,
due to overzealous optimization. If this happens to the kernel, I guess
that the other quick workaround is to add alignment directives or padding.
(A
More concern about compilers...
Most architectures mark the fields in their arch_spinlock_t structures
as volatile, which forces the compiler to respect the integrity of
those fields. Without volatile markings, the compiler is within its
rights to overwrite these fields, for example, by using a w
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