Re: [PATCH v2] arch: use WRITE_ONCE/READ_ONCE in smp_store_release/smp_load_acquire
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2015-08-03 01:42:06
Also in:
linux-arch, linux-arm-kernel, linux-mips, linux-s390, lkml, sparclinux
On Sun, 2015-08-02 at 17:11 +0200, Andrey Konovalov wrote:
Replace ACCESS_ONCE() macro in smp_store_release() and smp_load_acquire() with WRITE_ONCE() and READ_ONCE() on x86, arm, arm64, ia64, metag, mips, powerpc, s390, sparc and asm-generic since ACCESS_ONCE does not work reliably on non-scalar types.
.. and there are no restrictions on the argument to smp_load_acquire(), so it may be a non-scalar type. Though from a quick grep it looks like no one is doing that at the moment?
WRITE_ONCE() and READ_ONCE() were introduced in the commits 230fa253df63
("kernel: Provide READ_ONCE and ASSIGN_ONCE") and 43239cbe79fc ("kernel:
Change ASSIGN_ONCE(val, x) to WRITE_ONCE(x, val)").
Signed-off-by: Andrey Konovalov <redacted>
---
Changed in v2:
- Other archs besides x86.
arch/powerpc/include/asm/barrier.h | 4 ++--quoted hunk ↗ jump to hunk
diff --git a/arch/powerpc/include/asm/barrier.h b/arch/powerpc/include/asm/barrier.h index 51ccc72..0eca6ef 100644 --- a/arch/powerpc/include/asm/barrier.h +++ b/arch/powerpc/include/asm/barrier.h@@ -76,12 +76,12 @@ do { \ compiletime_assert_atomic_type(*p); \ smp_lwsync(); \ - ACCESS_ONCE(*p) = (v); \ + WRITE_ONCE(*p, v); \ } while (0) #define smp_load_acquire(p) \ ({ \ - typeof(*p) ___p1 = ACCESS_ONCE(*p); \ + typeof(*p) ___p1 = READ_ONCE(*p); \ compiletime_assert_atomic_type(*p); \ smp_lwsync(); \ ___p1; \
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc) cheers