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Commit db26217e authored May 29, 2015 by Will Deacon

arm64: atomic64_dec_if_positive: fix incorrect branch condition



If we attempt to atomic64_dec_if_positive on INT_MIN, we will underflow
and incorrectly decide that the original parameter was positive.

This patches fixes the broken condition code so that we handle this
corner case correctly.

Reviewed-by: Steve Capper <steve.capper@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

parent 6059a7b6

arch/arm64/include/asm/atomic_ll_sc.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -159,7 +159,7 @@ __LL_SC_PREFIX(atomic64_dec_if_positive(atomic64_t *v))
		" prfm pstl1strm, %2\n"
		"1: ldxr %0, %2\n"
		" subs %0, %0, #1\n"
		" b.mi 2f\n"
		" b.lt 2f\n"
		" stlxr %w1, %0, %2\n"
		" cbnz %w1, 1b\n"
		" dmb ish\n"

arch/arm64/include/asm/atomic_lse.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -291,7 +291,7 @@ static inline long atomic64_dec_if_positive(atomic64_t *v)
		/* LSE atomics */
		"1: ldr x30, %[v]\n"
		" subs %[ret], x30, #1\n"
		" b.mi 2f\n"
		" b.lt 2f\n"
		" casal x30, %[ret], %[v]\n"
		" sub x30, x30, #1\n"
		" sub x30, x30, %[ret]\n"