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由 Chuck Ebbert 提交于
_raw_spin_lock_flags() is entered with interrupts disabled. If it cannot obtain a spinlock, it checks the flags that were passed and re-enables interrupts before spinning if that's how the flags are set. When the spinlock might be available, it disables interrupts (even if they are already disabled) before trying to get the lock. Change that so interrupts are only disabled if they have been enabled. This costs nine bytes of duplicated spinloop code. Fastpath before patch: jle <keep looping> not-taken conditional jump cli disable interrupts jmp <try for lock> unconditional jump Fastpath after patch, if interrupts were not enabled: jg <try for lock> taken conditional branch Signed-off-by: NChuck Ebbert <76306.1226@compuserve.com> Acked-by: NIngo Molnar <mingo@elte.hu> Signed-off-by: NAndrew Morton <akpm@osdl.org> Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
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