Re: Q: perf_install_in_context/perf_event_enable are racy?

[Oleg Nesterov]

On 01/31, Peter Zijlstra wrote:
>
> On Mon, 2011-01-31 at 18:26 +0100, Oleg Nesterov wrote:
>
> > I do not understand the point of cpu_function_call() though, it looks
> > equal to smp_call_function_single() ?
>
> Very nearly so, except it takes a function that returns an int..

Ah, indeed...

> > >  	raw_spin_lock(&ctx->lock);
> > > -	ctx->is_active = 1;
> > > +	WARN_ON_ONCE(!ctx->is_active);
> >
> > This looks wrong if ctx->task == NULL.
>
> cpuctx->ctx should still have ->is_active = 1 I think.

Unless this is the first cpu counter, no?

Oleg.

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