arm64: introduce CONFIG_ARM64_LSE_ATOMICS as fallback to ll/sc atomics
In order to patch in the new atomic instructions at runtime, we need to generate wrappers around the out-of-line exclusive load/store atomics. This patch adds a new Kconfig option, CONFIG_ARM64_LSE_ATOMICS. which causes our atomic functions to branch to the out-of-line ll/sc implementations. To avoid the register spill overhead of the PCS, the out-of-line functions are compiled with specific compiler flags to force out-of-line save/restore of any registers that are usually caller-saved. Reviewed-by: NCatalin Marinas <catalin.marinas@arm.com> Signed-off-by: NWill Deacon <will.deacon@arm.com>
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arch/arm64/lib/atomic_ll_sc.c
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