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Groups > linux.kernel > #1600612 > unrolled thread
| Started by | Peter Zijlstra <peterz@infradead.org> |
|---|---|
| First post | 2017-03-14 16:40 +0100 |
| Last post | 2017-03-14 20:30 +0100 |
| Articles | 3 — 3 participants |
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Re: [PATCH] x86, kasan: add KASAN checks to atomic operations Peter Zijlstra <peterz@infradead.org> - 2017-03-14 16:40 +0100
Re: [PATCH] x86, kasan: add KASAN checks to atomic operations Mark Rutland <mark.rutland@arm.com> - 2017-03-14 16:50 +0100
Re: [PATCH] x86, kasan: add KASAN checks to atomic operations Dmitry Vyukov <dvyukov@google.com> - 2017-03-14 20:30 +0100
| From | Peter Zijlstra <peterz@infradead.org> |
|---|---|
| Date | 2017-03-14 16:40 +0100 |
| Subject | Re: [PATCH] x86, kasan: add KASAN checks to atomic operations |
| Message-ID | <tkWIi-25L-7@gated-at.bofh.it> |
On Tue, Mar 14, 2017 at 04:22:52PM +0100, Dmitry Vyukov wrote:
> -static __always_inline int atomic_read(const atomic_t *v)
> +static __always_inline int arch_atomic_read(const atomic_t *v)
> {
> - return READ_ONCE((v)->counter);
> + return READ_ONCE_NOCHECK((v)->counter);
Should NOCHEKC come with a comment, because i've no idea why this is so.
> }
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| From | Mark Rutland <mark.rutland@arm.com> |
|---|---|
| Date | 2017-03-14 16:50 +0100 |
| Message-ID | <tkWRX-29k-3@gated-at.bofh.it> |
| In reply to | #1600612 |
On Tue, Mar 14, 2017 at 04:32:30PM +0100, Peter Zijlstra wrote:
> On Tue, Mar 14, 2017 at 04:22:52PM +0100, Dmitry Vyukov wrote:
> > -static __always_inline int atomic_read(const atomic_t *v)
> > +static __always_inline int arch_atomic_read(const atomic_t *v)
> > {
> > - return READ_ONCE((v)->counter);
> > + return READ_ONCE_NOCHECK((v)->counter);
>
> Should NOCHEKC come with a comment, because i've no idea why this is so.
I suspect the idea is that given the wrapper will have done the KASAN
check, duplicating it here is either sub-optimal, or results in
duplicate splats. READ_ONCE() has an implicit KASAN check,
READ_ONCE_NOCHECK() does not.
If this is to solve duplicate splats, it'd be worth having a
WRITE_ONCE_NOCHECK() for arch_atomic_set().
Agreed on the comment, regardless.
Thanks,
Mark.
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| From | Dmitry Vyukov <dvyukov@google.com> |
|---|---|
| Date | 2017-03-14 20:30 +0100 |
| Message-ID | <tl0iS-4M7-13@gated-at.bofh.it> |
| In reply to | #1600627 |
On Tue, Mar 14, 2017 at 4:44 PM, Mark Rutland <mark.rutland@arm.com> wrote:
>> > -static __always_inline int atomic_read(const atomic_t *v)
>> > +static __always_inline int arch_atomic_read(const atomic_t *v)
>> > {
>> > - return READ_ONCE((v)->counter);
>> > + return READ_ONCE_NOCHECK((v)->counter);
>>
>> Should NOCHEKC come with a comment, because i've no idea why this is so.
>
> I suspect the idea is that given the wrapper will have done the KASAN
> check, duplicating it here is either sub-optimal, or results in
> duplicate splats. READ_ONCE() has an implicit KASAN check,
> READ_ONCE_NOCHECK() does not.
>
> If this is to solve duplicate splats, it'd be worth having a
> WRITE_ONCE_NOCHECK() for arch_atomic_set().
>
> Agreed on the comment, regardless.
Reverted xchg changes.
Added comments re READ_ONCE_NOCHECK() and WRITE_ONCE().
Added file comment.
Split into 3 patches and mailed.
Thanks!
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