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c20f326a62
This corrects a deadlock encountered on ap325 in the cases where the mutex is contended and the slow-path needs to be fallen back upon. Signed-off-by: Takashi YOSHII <yoshii.takashi@renesas.com> Signed-off-by: Kuninori Morimoto <morimoto.kuninori@renesas.com> Signed-off-by: Paul Mundt <lethal@linux-sh.org>
110 lines
2.6 KiB
C
110 lines
2.6 KiB
C
/*
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* arch/sh/include/asm/mutex-llsc.h
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*
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* SH-4A optimized mutex locking primitives
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*
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* Please look into asm-generic/mutex-xchg.h for a formal definition.
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*/
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#ifndef __ASM_SH_MUTEX_LLSC_H
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#define __ASM_SH_MUTEX_LLSC_H
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/*
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* Attempting to lock a mutex on SH4A is done like in ARMv6+ architecure.
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* with a bastardized atomic decrement (it is not a reliable atomic decrement
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* but it satisfies the defined semantics for our purpose, while being
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* smaller and faster than a real atomic decrement or atomic swap.
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* The idea is to attempt decrementing the lock value only once. If once
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* decremented it isn't zero, or if its store-back fails due to a dispute
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* on the exclusive store, we simply bail out immediately through the slow
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* path where the lock will be reattempted until it succeeds.
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*/
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static inline void
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__mutex_fastpath_lock(atomic_t *count, void (*fail_fn)(atomic_t *))
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{
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int __done, __res;
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__asm__ __volatile__ (
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"movli.l @%2, %0 \n"
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"add #-1, %0 \n"
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"movco.l %0, @%2 \n"
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"movt %1 \n"
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: "=&z" (__res), "=&r" (__done)
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: "r" (&(count)->counter)
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: "t");
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if (unlikely(!__done || __res != 0))
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fail_fn(count);
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}
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static inline int
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__mutex_fastpath_lock_retval(atomic_t *count, int (*fail_fn)(atomic_t *))
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{
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int __done, __res;
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__asm__ __volatile__ (
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"movli.l @%2, %0 \n"
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"add #-1, %0 \n"
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"movco.l %0, @%2 \n"
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"movt %1 \n"
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: "=&z" (__res), "=&r" (__done)
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: "r" (&(count)->counter)
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: "t");
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if (unlikely(!__done || __res != 0))
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__res = fail_fn(count);
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return __res;
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}
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static inline void
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__mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
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{
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int __done, __res;
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__asm__ __volatile__ (
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"movli.l @%2, %0 \n\t"
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"add #1, %0 \n\t"
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"movco.l %0, @%2 \n\t"
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"movt %1 \n\t"
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: "=&z" (__res), "=&r" (__done)
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: "r" (&(count)->counter)
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: "t");
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if (unlikely(!__done || __res <= 0))
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fail_fn(count);
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}
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/*
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* If the unlock was done on a contended lock, or if the unlock simply fails
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* then the mutex remains locked.
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*/
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#define __mutex_slowpath_needs_to_unlock() 1
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/*
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* For __mutex_fastpath_trylock we do an atomic decrement and check the
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* result and put it in the __res variable.
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*/
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static inline int
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__mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
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{
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int __res, __orig;
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__asm__ __volatile__ (
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"1: movli.l @%2, %0 \n\t"
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"dt %0 \n\t"
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"movco.l %0,@%2 \n\t"
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"bf 1b \n\t"
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"cmp/eq #0,%0 \n\t"
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"bt 2f \n\t"
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"mov #0, %1 \n\t"
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"bf 3f \n\t"
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"2: mov #1, %1 \n\t"
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"3: "
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: "=&z" (__orig), "=&r" (__res)
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: "r" (&count->counter)
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: "t");
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return __res;
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}
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#endif /* __ASM_SH_MUTEX_LLSC_H */
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