On Mon, May 16, 2016 at 12:55:57PM +0200, Peter Zijlstra wrote:
> > So the barriers already forbid that the compiler reorders code. How on earth
> > is the compiler supposed to optimize the dec/inc out?
>
> Order things like:
>
> > #define sched_preempt_enable_no_resched() \
> > do { \
> >
On Mon, May 16, 2016 at 12:55:57PM +0200, Peter Zijlstra wrote:
> You're right in that the 'proper' sequence:
>
> > #define preempt_enable() \
> > do { \
> > barrier(); \
> > if (unlikely(preempt_count_dec_and_test())) \
> > __preempt_schedule(); \
> > } while (0)
>
On Sat, May 14, 2016 at 05:39:37PM +0200, Thomas Gleixner wrote:
> I have a hard time to understand why the compiler optimizes out stuff w/o that
> patch.
>
> We already have:
>
> #define preempt_disable() \
> do { \
> preempt_count_inc(); \
> barrier(); \
> } while (0)
>
> #defi
On 5/14/2016 8:39 AM, Thomas Gleixner wrote:
On Fri, 13 May 2016, Vikram Mulukutla wrote:
On 5/13/2016 7:58 AM, Peter Zijlstra wrote:
diff --git a/include/asm-generic/preempt.h b/include/asm-generic/preempt.h
index 5d8ffa3e6f8c..c1cde3577551 100644
--- a/include/asm-generic/preempt.h
+++ b/incl
On Fri, 13 May 2016, Vikram Mulukutla wrote:
> On 5/13/2016 7:58 AM, Peter Zijlstra wrote:
> > diff --git a/include/asm-generic/preempt.h b/include/asm-generic/preempt.h
> > index 5d8ffa3e6f8c..c1cde3577551 100644
> > --- a/include/asm-generic/preempt.h
> > +++ b/include/asm-generic/preempt.h
> > @
On 5/13/2016 7:58 AM, Peter Zijlstra wrote:
On Thu, May 12, 2016 at 11:39:47PM -0700, Vikram Mulukutla wrote:
Hi,
I came across a piece of engineering code that looked like:
preempt_disable();
/* --cut, lots of code-- */
preempt_enable_no_resched();
put_user()
preempt_disable();
(If you wish
On Thu, May 12, 2016 at 11:39:47PM -0700, Vikram Mulukutla wrote:
> Hi,
>
> I came across a piece of engineering code that looked like:
>
> preempt_disable();
> /* --cut, lots of code-- */
> preempt_enable_no_resched();
> put_user()
> preempt_disable();
>
> (If you wish to seriously question the
On Thu, 12 May 2016, Vikram Mulukutla wrote:
> preempt_disable();
> /* --cut, lots of code-- */
> preempt_enable_no_resched();
> put_user()
> preempt_disable();
>
> (If you wish to seriously question the usage of the preempt API in this
> manner, I unfortunately have no comment since I didn't writ
Hi,
I came across a piece of engineering code that looked like:
preempt_disable();
/* --cut, lots of code-- */
preempt_enable_no_resched();
put_user()
preempt_disable();
(If you wish to seriously question the usage of the preempt API in this
manner, I unfortunately have no comment since I didn
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