Re: [PATCH] arm64: kcsan: Fix kcsan test_barrier fail and panic

[Kefeng Wang]

On 2022/4/26 20:10, Marco Elver wrote:
> On Tue, Apr 26, 2022 at 08:17AM +0000, Kefeng Wang wrote:
> > As "kcsan: Support detecting a subset of missing memory barriers"
> > introduced KCSAN_STRICT which make kcsan detects more missing memory
> > barrier, but arm64 don't have KCSAN instrumentation for barriers, so
> > the new selftest test_barrier() will fail, then panic.
> Thanks for fixing this - did kcsan_test module pass as well?

Yes， selftest and kcsan_test  passed with gcc11 & clang 14.

...

> > +#ifdef __dma_mb
> > +#define dma_mb()	do { kcsan_mb(); __dma_mb(); } while (0)
> > +#endif
> > +
> So it looks like arm64 is the only arch that defines dma_mb(). By adding
> it to asm-generic, we'd almost be encouraging other architectures to add
> it, which I don't know we want.
>
> Documentation/memory-barriers.txt doesn't mention dma_mb() either - so
> perhaps dma_mb() doesn't belong in asm-generic/barrier.h, and you could
> only change arm64's definition of dma_mb() to add the kcsan_mb().
>
> Preferences? Maybe arch64 maintainers have more background on why arm64
> is an anomaly here.
> .
Let's wait to see aarch64 maintainers's suggestion.