Re: [tip:locking/urgent] compiler, atomics: Provide READ_ONCE_NOCHECK ()

[Peter Zijlstra <peterz@xxxxxxxxxxxxx>]

On Wed, Oct 14, 2015 at 09:23:33AM -0700, Andy Lutomirski wrote:
> On Wed, Oct 14, 2015 at 9:20 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> > On Wed, Oct 14, 2015 at 06:18:58PM +0200, Dmitry Vyukov wrote:
> >>
> >> Well, if another thread writes it byte-by-byte, it pretty much does
> >> not matter how you read it.
> >> Note that I said "at least one access is not atomic". If both are
> >> atomic, then this is, of course, legal. And KTSAN considers
> >> READ/WRITE_ONCE as atomic operations.
> >
> > OK, then I'm confused on what exactly the annotation does, but less
> > worried.
> 
> The annotation says "hey, KASAN (etc), don't worry if you think that
> the memory being accessed is out of bounds".  Presumably KTSAN is okay
> with the operation because it's atomic, but KASAN dislikes it because
> it's accessing memory that is out of bounds from the perspective of a
> C program.

There's going to be more of that..

> I'd still rather find a way to just delete get_wchan, but whatever.

:-)
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