Re: [PATCH v2] ipc/msg: Implement lockless pipelined wakeups

[Davidlohr Bueso]

On Wed, 04 Nov 2015, Peter Zijlstra wrote:

> On Tue, Nov 03, 2015 at 04:03:29PM +0100, Sebastian Andrzej Siewior wrote:
>
> > -	struct msg_msg		*volatile r_msg;
> > +	struct msg_msg		*r_msg;
>
> > +				wake_q_add(wake_q, msr->r_tsk);
> >  				msr->r_msg = msg;
> > +				/*
> > +				 * Rely on the implicit cmpxchg barrier from
> > +				 * wake_q_add such that we can ensure that
>
> Davidlohr, didn't you want to make that cmpxchg_relaxed() or
> cmpxchg_release() ?

Right, I had forgotten about that. iirc we ended up deciding to fully
relax the cmpxchg and update the callers instead.
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