Re: Patch for drm-next WAS Re: [PATCH] kref: prefer atomic_inc_not_zero to atomic_add_unless
On Tue, Jul 12, 2016 at 2:28 PM, Daniel Vetter wrote: > Sure can do, but I can't find the raw patch anywhere (I suck, I know). > Care to resend? Hey sorry I missed this email requesting the actual patch. I reposted it here: https://lkml.org/lkml/2016/12/14/814
Re: Patch for drm-next WAS Re: [PATCH] kref: prefer atomic_inc_not_zero to atomic_add_unless
On Fri, Jul 01, 2016 at 09:08:34AM +0200, Thomas Hellstrom wrote:
> Dave,
>
> Since kref_get_unless_zero() was brought in by drm, could we add this to
> drm-next?
Sure can do, but I can't find the raw patch anywhere (I suck, I know).
Care to resend?
Thanks, Daniel
>
> Thanks,
> Thomas
>
>
> On 06/30/2016 12:52 AM, Jason A. Donenfeld wrote:
> > This was positively reviewed by maintainers but never picked up. Can
> > someone queue this for 4.7 or 4.8?
> >
> > Thanks,
> > Jason
> >
> > On Mon, Feb 1, 2016 at 10:53 PM, Jason A. Donenfeld wrote:
> >> This was positively reviewed but never picked up. Can someone queue
> >> this for rc3?
> >>
> >> Thanks,
> >> Jason
> >>
> >> On Sun, Oct 11, 2015 at 9:59 PM, Thomas Hellstrom
> >> wrote:
> >>> Reviewed-by: Thomas Hellstrom
> >>>
> >>>
> >>> On 10/10/2015 12:56 PM, Jason A. Donenfeld wrote:
> On most platforms, there exists this ifdef:
>
> #define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
>
> This makes this patch functionally useless. However, on PPC, there is
> actually an explicit definition of atomic_inc_not_zero with its own
> assembly that is slightly more optimized than atomic_add_unless. So,
> this patch changes kref to use atomic_inc_not_zero instead, for PPC and
> any future platforms that might provide an explicit implementation.
>
> This also puts this usage of kref more in line with a verbatim reading
> of the examples in Paul McKenney's paper [1] in the section titled "2.4
> Atomic Counting With Check and Release Memory Barrier", which uses
> atomic_inc_not_zero.
>
> [1]
> https://urldefense.proofpoint.com/v2/url?u=http-3A__open-2Dstd.org_jtc1_sc22_wg21_docs_papers_2007_n2167.pdf&d=BQIBAg&c=Sqcl0Ez6M0X8aeM67LKIiDJAXVeAw-YihVMNtXt-uEs&r=vpukPkBtpoNQp2IUKuFviOmPNYWVKmen3Jeeu55zmEA&m=z5Nd9sYiJMKiphNjyZp6XT5CbayXMBlcb903f260pDY&s=HEHX3CuXRs2GRRQWuC4Vef6iJMwdilKVRkiZgJpjEpA&e=
>
> Signed-off-by: Jason A. Donenfeld
> ---
> include/linux/kref.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/kref.h b/include/linux/kref.h
> index 484604d..83d1f94 100644
> --- a/include/linux/kref.h
> +++ b/include/linux/kref.h
> @@ -166,6 +166,6 @@ static inline int kref_put_mutex(struct kref *kref,
> */
> static inline int __must_check kref_get_unless_zero(struct kref *kref)
> {
> - return atomic_add_unless(&kref->refcount, 1, 0);
> + return atomic_inc_not_zero(&kref->refcount);
> }
> #endif /* _KREF_H_ */
>
>
> ___
> dri-devel mailing list
> dri-de...@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
Patch for drm-next WAS Re: [PATCH] kref: prefer atomic_inc_not_zero to atomic_add_unless
Dave,
Since kref_get_unless_zero() was brought in by drm, could we add this to
drm-next?
Thanks,
Thomas
On 06/30/2016 12:52 AM, Jason A. Donenfeld wrote:
> This was positively reviewed by maintainers but never picked up. Can
> someone queue this for 4.7 or 4.8?
>
> Thanks,
> Jason
>
> On Mon, Feb 1, 2016 at 10:53 PM, Jason A. Donenfeld wrote:
>> This was positively reviewed but never picked up. Can someone queue
>> this for rc3?
>>
>> Thanks,
>> Jason
>>
>> On Sun, Oct 11, 2015 at 9:59 PM, Thomas Hellstrom
>> wrote:
>>> Reviewed-by: Thomas Hellstrom
>>>
>>>
>>> On 10/10/2015 12:56 PM, Jason A. Donenfeld wrote:
On most platforms, there exists this ifdef:
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
This makes this patch functionally useless. However, on PPC, there is
actually an explicit definition of atomic_inc_not_zero with its own
assembly that is slightly more optimized than atomic_add_unless. So,
this patch changes kref to use atomic_inc_not_zero instead, for PPC and
any future platforms that might provide an explicit implementation.
This also puts this usage of kref more in line with a verbatim reading
of the examples in Paul McKenney's paper [1] in the section titled "2.4
Atomic Counting With Check and Release Memory Barrier", which uses
atomic_inc_not_zero.
[1]
https://urldefense.proofpoint.com/v2/url?u=http-3A__open-2Dstd.org_jtc1_sc22_wg21_docs_papers_2007_n2167.pdf&d=BQIBAg&c=Sqcl0Ez6M0X8aeM67LKIiDJAXVeAw-YihVMNtXt-uEs&r=vpukPkBtpoNQp2IUKuFviOmPNYWVKmen3Jeeu55zmEA&m=z5Nd9sYiJMKiphNjyZp6XT5CbayXMBlcb903f260pDY&s=HEHX3CuXRs2GRRQWuC4Vef6iJMwdilKVRkiZgJpjEpA&e=
Signed-off-by: Jason A. Donenfeld
---
include/linux/kref.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/kref.h b/include/linux/kref.h
index 484604d..83d1f94 100644
--- a/include/linux/kref.h
+++ b/include/linux/kref.h
@@ -166,6 +166,6 @@ static inline int kref_put_mutex(struct kref *kref,
*/
static inline int __must_check kref_get_unless_zero(struct kref *kref)
{
- return atomic_add_unless(&kref->refcount, 1, 0);
+ return atomic_inc_not_zero(&kref->refcount);
}
#endif /* _KREF_H_ */
