tree 446a2926a21557be1efc95fa025f9ee30f330462
parent ec89ab50a03a33a4a648869e868b1964354fb2d1
author Will Deacon <will.deacon@arm.com> 1517400740 +0000
committer Catalin Marinas <catalin.marinas@arm.com> 1517957591 +0000

arm64: spinlock: Fix theoretical trylock() A-B-A with LSE atomics

If the spinlock "next" ticket wraps around between the initial LDR
and the cmpxchg in the LSE version of spin_trylock, then we can erroneously
think that we have successfuly acquired the lock because we only check
whether the next ticket return by the cmpxchg is equal to the owner ticket
in our updated lock word.

This patch fixes the issue by performing a full 32-bit check of the lock
word when trying to determine whether or not the CASA instruction updated
memory.

Reported-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>