ARM: 7812/1: rwlocks: retry trylock operation if strex fails on free lock (00efaa02) · Commits · 戴 / test

arch/arm/include/asm/spinlock.h

+30 −19

Original line number	Original line	Diff line number	Diff line
	@@ -168,17 +168,20 @@ static inline void arch_write_lock(arch_rwlock_t *rw)

	static inline int arch_write_trylock(arch_rwlock_t *rw)		static inline int arch_write_trylock(arch_rwlock_t *rw)
	{		{
	unsigned long tmp;		unsigned long contended, res;

			do {
	__asm__ __volatile__(		__asm__ __volatile__(
	" ldrex %0, [%1]\n"		" ldrex %0, [%2]\n"
			" mov %1, #0\n"
	" teq %0, #0\n"		" teq %0, #0\n"
	" strexeq %0, %2, [%1]"		" strexeq %1, %3, [%2]"
	: "=&r" (tmp)		: "=&r" (contended), "=&r" (res)
	: "r" (&rw->lock), "r" (0x80000000)		: "r" (&rw->lock), "r" (0x80000000)
	: "cc");		: "cc");
			} while (res);

	if (tmp == 0) {		if (!contended) {
	smp_mb();		smp_mb();
	return 1;		return 1;
	} else {		} else {
	@@ -254,18 +257,26 @@ static inline void arch_read_unlock(arch_rwlock_t *rw)

	static inline int arch_read_trylock(arch_rwlock_t *rw)		static inline int arch_read_trylock(arch_rwlock_t *rw)
	{		{
	unsigned long tmp, tmp2 = 1;		unsigned long contended, res;

			do {
	__asm__ __volatile__(		__asm__ __volatile__(
	" ldrex %0, [%2]\n"		" ldrex %0, [%2]\n"
			" mov %1, #0\n"
	" adds %0, %0, #1\n"		" adds %0, %0, #1\n"
	" strexpl %1, %0, [%2]\n"		" strexpl %1, %0, [%2]"
	: "=&r" (tmp), "+r" (tmp2)		: "=&r" (contended), "=&r" (res)
	: "r" (&rw->lock)		: "r" (&rw->lock)
	: "cc");		: "cc");
			} while (res);

			/* If the lock is negative, then it is already held for write. */
			if (contended < 0x80000000) {
	smp_mb();		smp_mb();
	return tmp2 == 0;		return 1;
			} else {
			return 0;
			}
	}		}

	/* read_can_lock - would read_trylock() succeed? */		/* read_can_lock - would read_trylock() succeed? */

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