On Thu, Dec 17, 2020 at 11:48:23AM +0100, Peter Zijlstra wrote:
> On Wed, Dec 16, 2020 at 01:19:31PM -0800, Paul E. McKenney wrote:
> > Given that there is no optimization potential, then the main reason to use
> > data_race() instead of *_ONCE() is to prevent KCSAN from considering the
> >
On Wed, Dec 16, 2020 at 01:19:31PM -0800, Paul E. McKenney wrote:
> Given that there is no optimization potential, then the main reason to use
> data_race() instead of *_ONCE() is to prevent KCSAN from considering the
> accesses when looking for data races. But that is mostly for debugging
>
On Wed, Dec 16, 2020 at 10:23:57PM +0100, Thomas Gleixner wrote:
> On Wed, Dec 16 2020 at 13:19, Paul E. McKenney wrote:
> > On Wed, Dec 16, 2020 at 01:27:43AM +0100, Thomas Gleixner wrote:
> >> So my intent was to document that this code does not care about anything
> >> else than what I'd
On Wed, Dec 16 2020 at 13:19, Paul E. McKenney wrote:
> On Wed, Dec 16, 2020 at 01:27:43AM +0100, Thomas Gleixner wrote:
>> So my intent was to document that this code does not care about anything
>> else than what I'd consider to be plain compiler bugs.
>>
>> My conclusion might be wrong as
On Wed, Dec 16, 2020 at 01:27:43AM +0100, Thomas Gleixner wrote:
> On Tue, Dec 08 2020 at 07:03, Paul E. McKenney wrote:
>
> > On Tue, Dec 08, 2020 at 09:11:29AM +0100, Peter Zijlstra wrote:
> >> On Mon, Dec 07, 2020 at 11:44:06AM -0800, Paul E. McKenney wrote:
> >>
> >> > Also, in this
On Tue, Dec 08 2020 at 07:03, Paul E. McKenney wrote:
> On Tue, Dec 08, 2020 at 09:11:29AM +0100, Peter Zijlstra wrote:
>> On Mon, Dec 07, 2020 at 11:44:06AM -0800, Paul E. McKenney wrote:
>>
>> > Also, in this particular case, why data_race() rather than READ_ONCE()?
>> > Do we really expect
On Tue, Dec 08, 2020 at 09:11:29AM +0100, Peter Zijlstra wrote:
> On Mon, Dec 07, 2020 at 11:44:06AM -0800, Paul E. McKenney wrote:
>
> > Also, in this particular case, why data_race() rather than READ_ONCE()?
> > Do we really expect the compiler to be able to optimize this case
> > significantly
On Mon, Dec 07, 2020 at 11:44:06AM -0800, Paul E. McKenney wrote:
> Also, in this particular case, why data_race() rather than READ_ONCE()?
> Do we really expect the compiler to be able to optimize this case
> significantly without READ_ONCE()?
It's about intent and how the code reads.
On Mon, Dec 07, 2020 at 07:19:51PM +0100, Marco Elver wrote:
> On Mon, 7 Dec 2020 at 18:46, Thomas Gleixner wrote:
> > On Mon, Dec 07 2020 at 13:09, Peter Zijlstra wrote:
> > > On Sun, Dec 06, 2020 at 10:12:56PM +0100, Thomas Gleixner wrote:
> > >> +if (data_race(tick_do_timer_cpu) ==
On Mon, Dec 07, 2020 at 11:46:48PM +0100, Thomas Gleixner wrote:
> On Mon, Dec 07 2020 at 14:38, Paul E. McKenney wrote:
>
> > On Mon, Dec 07, 2020 at 10:46:33PM +0100, Thomas Gleixner wrote:
> >> On Mon, Dec 07 2020 at 11:44, Paul E. McKenney wrote:
> >> > On Mon, Dec 07, 2020 at 07:19:51PM
On Mon, Dec 07 2020 at 14:38, Paul E. McKenney wrote:
> On Mon, Dec 07, 2020 at 10:46:33PM +0100, Thomas Gleixner wrote:
>> On Mon, Dec 07 2020 at 11:44, Paul E. McKenney wrote:
>> > On Mon, Dec 07, 2020 at 07:19:51PM +0100, Marco Elver wrote:
>> >> On Mon, 7 Dec 2020 at 18:46, Thomas Gleixner
On Mon, Dec 07, 2020 at 10:46:33PM +0100, Thomas Gleixner wrote:
> On Mon, Dec 07 2020 at 11:44, Paul E. McKenney wrote:
> > On Mon, Dec 07, 2020 at 07:19:51PM +0100, Marco Elver wrote:
> >> On Mon, 7 Dec 2020 at 18:46, Thomas Gleixner wrote:
> >> I currently don't know what the rule for Peter's
On Mon, Dec 07 2020 at 11:44, Paul E. McKenney wrote:
> On Mon, Dec 07, 2020 at 07:19:51PM +0100, Marco Elver wrote:
>> On Mon, 7 Dec 2020 at 18:46, Thomas Gleixner wrote:
>> I currently don't know what the rule for Peter's preferred variant
>> would be, without running the risk of some
On Mon, Dec 07, 2020 at 07:19:51PM +0100, Marco Elver wrote:
> On Mon, 7 Dec 2020 at 18:46, Thomas Gleixner wrote:
> > On Mon, Dec 07 2020 at 13:09, Peter Zijlstra wrote:
> > > On Sun, Dec 06, 2020 at 10:12:56PM +0100, Thomas Gleixner wrote:
> > >> +if (data_race(tick_do_timer_cpu) ==
On Mon, Dec 07 2020 at 19:19, Marco Elver wrote:
> On Mon, 7 Dec 2020 at 18:46, Thomas Gleixner wrote:
>> On Mon, Dec 07 2020 at 13:09, Peter Zijlstra wrote:
>> > I prefer the form:
>> >
>> > if (data_race(tick_do_timer_cpu == TICK_DO_TIMER_BOOT)) {
>> >
>> > But there doesn't yet seem to
On Mon, 7 Dec 2020 at 18:46, Thomas Gleixner wrote:
> On Mon, Dec 07 2020 at 13:09, Peter Zijlstra wrote:
> > On Sun, Dec 06, 2020 at 10:12:56PM +0100, Thomas Gleixner wrote:
> >> +if (data_race(tick_do_timer_cpu) == TICK_DO_TIMER_BOOT) {
> >
> > I prefer the form:
> >
> > if
On Mon, Dec 07 2020 at 13:09, Peter Zijlstra wrote:
> On Sun, Dec 06, 2020 at 10:12:56PM +0100, Thomas Gleixner wrote:
>> +if (data_race(tick_do_timer_cpu) == TICK_DO_TIMER_BOOT) {
>
> I prefer the form:
>
> if (data_race(tick_do_timer_cpu == TICK_DO_TIMER_BOOT)) {
>
> But there
On Sun, Dec 06, 2020 at 10:12:56PM +0100, Thomas Gleixner wrote:
> + if (data_race(tick_do_timer_cpu) == TICK_DO_TIMER_BOOT) {
I prefer the form:
if (data_race(tick_do_timer_cpu == TICK_DO_TIMER_BOOT)) {
But there doesn't yet seem to be sufficient data_race() usage in the
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