Messages in this thread | | | Date | Wed, 4 Jul 2018 16:56:19 +0100 | From | Mark Rutland <> | Subject | Re: [PATCHv2 06/11] atomics/treewide: rework ordering barriers |
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On Wed, Jul 04, 2018 at 04:06:46PM +0100, Will Deacon wrote: > On Mon, Jun 25, 2018 at 11:59:47AM +0100, Mark Rutland wrote: > > Currently architectures can override __atomic_op_*() to define the barriers > > used before/after a relaxed atomic when used to build acquire/release/fence > > variants. > > > > This has the unfortunate property of requiring the architecture to define the > > full wrapper for the atomics, rather than just the barriers they care about, > > and gets in the way of generating atomics which can be easily read. > > > > Instead, this patch has architectures define an optional set of barriers, > > __atomic_mb_{before,after}_{acquire,release,fence}(), which <linux/atomic.h> > > uses to build the wrappers. > > Looks like you've renamed these in the patch but not updated the commit > message.
Yup; Peter also pointed that out. In my branch this now looks like:
---- Instead, this patch has architectures define an optional set of barriers:
* __atomic_acquire_fence() * __atomic_release_fence() * __atomic_pre_fence() * __atomic_post_fence()
... which <linux/atomic.h> uses to build the wrappers. ----
... which is hopefully more legible, too!
> Also, to add to the bikeshedding, would it worth adding "rmw" in there > somewhere, e.g. __atomic_post_rmw_fence, since I assume these only > apply to value-returning stuff?
I don't have any opinion there, but I'm also not sure I've parsed your rationale correctly. I guess a !RMW full-fence op doesn't make sense? Or that's something we want to avoid in the API?
AFAICT, we only use __atomic_{pre,post}_fence() for RMW ops today.
Thanks, Mark.
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