Messages in this thread | | | Subject | Re: [PATCH] locking/atomics: don't alias ____ptr | From | Andrey Ryabinin <> | Date | Wed, 28 Jun 2017 17:00:15 +0300 |
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On 06/28/2017 04:20 PM, Thomas Gleixner wrote: > On Wed, 28 Jun 2017, Sebastian Andrzej Siewior wrote: >> On 2017-06-28 14:15:18 [+0300], Andrey Ryabinin wrote: >>> The main problem here is that arch_cmpxchg64_local() calls cmpxhg_local() instead of using arch_cmpxchg_local(). >>> >>> So, the patch bellow should fix the problem, also this will fix double instrumentation of cmpcxchg64[_local](). >>> But I haven't tested this patch yet. >> >> tested, works. Next step? > > Check all other implementations in every architecture whether there is a > similar problem ..... >
This and similar problems could have been caught by -Wshadow warning:
In file included from ../arch/x86/include/asm/atomic.h:282:0, from ../include/linux/atomic.h:4, from ../include/linux/jump_label.h:183, from ../arch/x86/include/asm/string_64.h:5, from ../arch/x86/include/asm/string.h:4, from ../include/linux/string.h:18, from ../include/linux/bitmap.h:8, from ../drivers/iommu/intel-iommu.c:24: ../include/asm-generic/atomic-instrumented.h:376:18: warning: declaration of ‘____ptr’ shadows a previous local [-Wshadow] __typeof__(ptr) ____ptr = (ptr); \ ^ ../arch/x86/include/asm/cmpxchg_64.h:18:2: note: in expansion of macro ‘cmpxchg_local’ cmpxchg_local((ptr), (o), (n)); \ ^ ../include/asm-generic/atomic-instrumented.h:392:2: note: in expansion of macro ‘arch_cmpxchg64_local’ arch_cmpxchg64_local(____ptr, (old), (new)); \ ^ ../drivers/iommu/intel-iommu.c:2290:9: note: in expansion of macro ‘cmpxchg64_local’ tmp = cmpxchg64_local(&pte->val, 0ULL, pteval); ^ ../include/asm-generic/atomic-instrumented.h:390:18: note: shadowed declaration is here __typeof__(ptr) ____ptr = (ptr); \ ^ ../drivers/iommu/intel-iommu.c:2290:9: note: in expansion of macro ‘cmpxchg64_local’ tmp = cmpxchg64_local(&pte->val, 0ULL, pteval); ^
But for some reason we use -Wshadow only on W=2 level.
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