Messages in this thread | | | Date | Mon, 11 Nov 2019 23:38:26 +0100 | From | Frederic Weisbecker <> | Subject | Re: [RFC PATCH 4/4] irq_work: Weaken ordering in irq_work_run_list() |
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On Mon, Nov 11, 2019 at 09:43:13AM +0100, Peter Zijlstra wrote: > On Fri, Nov 08, 2019 at 05:08:58PM +0100, Frederic Weisbecker wrote: > > > diff --git a/kernel/irq_work.c b/kernel/irq_work.c > > index 49c53f80a13a..b709ab05cbfd 100644 > > --- a/kernel/irq_work.c > > +++ b/kernel/irq_work.c > > @@ -34,8 +34,8 @@ static bool irq_work_claim(struct irq_work *work) > > oflags = atomic_fetch_or(IRQ_WORK_CLAIMED, &work->flags); > > /* > > * If the work is already pending, no need to raise the IPI. > > + * The pairing atomic_andnot() followed by a barrier in irq_work_run() > > + * makes sure everything we did before is visible. > > */ > > if (oflags & IRQ_WORK_PENDING) > > return false; > > > @@ -151,14 +151,16 @@ static void irq_work_run_list(struct llist_head *list) > > * to claim that work don't rely on us to handle their data > > * while we are in the middle of the func. > > */ > > - flags = atomic_fetch_andnot(IRQ_WORK_PENDING, &work->flags); > > + atomic_andnot(IRQ_WORK_PENDING, &work->flags); > > + smp_mb__after_atomic(); > > I think I'm prefering you use: > > flags = atomic_fetch_andnot_acquire(IRQ_WORK_PENDING, &work->flags);
Ah good point. Preparing that.
> > Also, I'm cursing at myself for the horrible comments here.
Hmm, I wrote many of those, which one? :o)
Thanks.
> > > work->func(work); > > /* > > * Clear the BUSY bit and return to the free state if > > * no-one else claimed it meanwhile. > > */ > > - (void)atomic_cmpxchg(&work->flags, flags, flags & ~IRQ_WORK_BUSY); > > + (void)atomic_cmpxchg(&work->flags, flags & ~IRQ_WORK_PENDING, > > + flags & ~IRQ_WORK_CLAIMED); > > } > > } > > > > -- > > 2.23.0 > >
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