Re: [PATCH 1/3] perf: add context field to perf_event

[Joerg Roedel]

On Tue, Jul 12, 2011 at 11:31:00AM +0200, Peter Zijlstra wrote:
> On Tue, 2011-07-12 at 12:27 +0300, Avi Kivity wrote:

> > But it means that 'current' is not set to the right value.  If the 
> > function depends on it, then it will misbehave.  And in fact 
> > preempt_notifier_register(), which is the function we want to call here, 
> > does depend on current.
> > 
> > Of course we need to find more users for this, but I have a feeling this 
> > will be generally useful.  The alternative is to keep adding bits to 
> > thread_info::flags.
> 
> Using TIF_bits sounds like a much better solution for this, wakeups are
> really rather expensive and its best to avoid extra if at all possible.

I would rather vote for Avi's solution too. Such a functionality is very
helpful for LWP-perf integration as well (because we need a way to call
do_mmap for a task != current).

Regards,

	Joerg

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