Messages in this thread Patch in this message | | | Date | Tue, 26 Apr 2022 14:10:06 +0200 | From | Marco Elver <> | Subject | Re: [PATCH] arm64: kcsan: Fix kcsan test_barrier fail and panic |
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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?
> Let's prefix all barriers with __ on arm64, as asm-generic/barriers.h > defined the final instrumented version of these barriers, which will > fix the above issues. > > Fixes: dd03762ab608 ("arm64: Enable KCSAN") > Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com> > --- > arch/arm64/include/asm/barrier.h | 12 ++++++------ > include/asm-generic/barrier.h | 4 ++++ > 2 files changed, 10 insertions(+), 6 deletions(-) > > diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h > index 62217be36217..9760a8d4ed0a 100644 > --- a/arch/arm64/include/asm/barrier.h > +++ b/arch/arm64/include/asm/barrier.h > @@ -46,13 +46,13 @@ > #define pmr_sync() do {} while (0) > #endif > > -#define mb() dsb(sy) > -#define rmb() dsb(ld) > -#define wmb() dsb(st) > +#define __mb() dsb(sy) > +#define __rmb() dsb(ld) > +#define __wmb() dsb(st) > > -#define dma_mb() dmb(osh) > -#define dma_rmb() dmb(oshld) > -#define dma_wmb() dmb(oshst) > +#define __dma_mb() dmb(osh) > +#define __dma_rmb() dmb(oshld) > +#define __dma_wmb() dmb(oshst) > > #define io_stop_wc() dgh() > > diff --git a/include/asm-generic/barrier.h b/include/asm-generic/barrier.h > index fd7e8fbaeef1..18863c50e9ce 100644 > --- a/include/asm-generic/barrier.h > +++ b/include/asm-generic/barrier.h > @@ -38,6 +38,10 @@ > #define wmb() do { kcsan_wmb(); __wmb(); } while (0) > #endif > > +#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.
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