Re: [PATCH 1/8] kcsan: Add Kernel Concurrency Sanitizer infrastructure

Marco Elver
2019-10-17T07:49:40Z

On Thu, 17 Oct 2019 at 09:47, Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Wed, Oct 16, 2019 at 09:34:05PM +0200, Marco Elver wrote:
> > On Wed, 16 Oct 2019 at 20:44, Peter Zijlstra <peterz@infradead.org> wrote:
> > > > + /*
> > > > + * Disable interrupts & preemptions, to ignore races due to accesses in
> > > > + * threads running on the same CPU.
> > > > + */
> > > > + local_irq_save(irq_flags);
> > > > + preempt_disable();
> > >
> > > Is there a point to that preempt_disable() here?
> >
> > We want to avoid being preempted while the watchpoint is set up;
> > otherwise, we would report data-races for CPU-local data, which is
> > incorrect.
>
> Disabling IRQs already very much disables preemption. There is
> absolutely no point in doing preempt_disable() when the whole section
> already runs with IRQs disabled.

Ah thanks for the clarification, in that case I assume it's safe to
remove preempt_disable() for v2.

> --
> You received this message because you are subscribed to the Google Groups "kasan-dev" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/20191017074730.GW2328%40hirez.programming.kicks-ass.net.