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Date: Fri, 27 Feb 2015 00:46:55 -0500 From: Pranith Kumar <bobby.prani@...il.com> To: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will.deacon@....com>, Steve Capper <steve.capper@...aro.org>, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org (open list) Subject: [RFC PATCH] ARM64: cmpxchg.h: Clear the exclusive access bit on fail In cmpxchg(), we do a load exclusive on an address and upon a comparison fail, we skip the store exclusive instruction. This can result in the exclusive bit still set. If there was a store exclusive after this to the same address, that will see the exclusive bit set. This should not happen. We need to clear the exclusive bit in these cases. Signed-off-by: Pranith Kumar <bobby.prani@...il.com> --- arch/arm64/include/asm/cmpxchg.h | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/arch/arm64/include/asm/cmpxchg.h b/arch/arm64/include/asm/cmpxchg.h index cb95930..ed2cf90 100644 --- a/arch/arm64/include/asm/cmpxchg.h +++ b/arch/arm64/include/asm/cmpxchg.h @@ -94,7 +94,7 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old, " cmp %w1, %w3\n" " b.ne 1f\n" " stxrb %w0, %w4, %2\n" - "1:\n" + "1: clrex\n" : "=&r" (res), "=&r" (oldval), "+Q" (*(u8 *)ptr) : "Ir" (old), "r" (new) : "cc"); @@ -109,7 +109,7 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old, " cmp %w1, %w3\n" " b.ne 1f\n" " stxrh %w0, %w4, %2\n" - "1:\n" + "1: clrex\n" : "=&r" (res), "=&r" (oldval), "+Q" (*(u16 *)ptr) : "Ir" (old), "r" (new) : "cc"); @@ -124,7 +124,7 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old, " cmp %w1, %w3\n" " b.ne 1f\n" " stxr %w0, %w4, %2\n" - "1:\n" + "1: clrex\n" : "=&r" (res), "=&r" (oldval), "+Q" (*(u32 *)ptr) : "Ir" (old), "r" (new) : "cc"); @@ -139,7 +139,7 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old, " cmp %1, %3\n" " b.ne 1f\n" " stxr %w0, %4, %2\n" - "1:\n" + "1: clrex\n" : "=&r" (res), "=&r" (oldval), "+Q" (*(u64 *)ptr) : "Ir" (old), "r" (new) : "cc"); @@ -173,7 +173,7 @@ static inline int __cmpxchg_double(volatile void *ptr1, volatile void *ptr2, " mov %w0, #0\n" " cbnz %1, 1f\n" " stxp %w0, %5, %6, %2\n" - "1:\n" + "1: clrex\n" : "=&r"(loop), "=&r"(lost), "+Q" (*(u64 *)ptr1) : "r" (old1), "r"(old2), "r"(new1), "r"(new2)); } while (loop); -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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