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Commit 00efaa02 authored by Will Deacon's avatar Will Deacon Committed by Russell King
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ARM: 7812/1: rwlocks: retry trylock operation if strex fails on free lock 



Commit 15e7e5c1 ("ARM: 7749/1: spinlock: retry trylock operation if
strex fails on free lock") modifying our arch_spin_trylock to retry the
acquisition if the lock appeared uncontended, but the strex failed.

This patch does the same for rwlocks, which were missed by the original
patch.

Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent afa31d8e

arch/arm/include/asm/spinlock.h

+30 −19
Original line number 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)

{

	unsigned long tmp;

	unsigned long contended, res;



	do {

		__asm__ __volatile__(

"	ldrex	%0, [%1]\n"

		"	ldrex	%0, [%2]\n"

		"	mov	%1, #0\n"

		"	teq	%0, #0\n"

"	strexeq	%0, %2, [%1]"

	: "=&r" (tmp)

		"	strexeq	%1, %3, [%2]"

		: "=&r" (contended), "=&r" (res)

		: "r" (&rw->lock), "r" (0x80000000)

		: "cc");

	} while (res);



	if (tmp == 0) {

	if (!contended) {

		smp_mb();

		return 1;

	} 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)

{

	unsigned long tmp, tmp2 = 1;

	unsigned long contended, res;



	do {

		__asm__ __volatile__(

		"	ldrex	%0, [%2]\n"

		"	mov	%1, #0\n"

		"	adds	%0, %0, #1\n"

"	strexpl	%1, %0, [%2]\n"

	: "=&r" (tmp), "+r" (tmp2)

		"	strexpl	%1, %0, [%2]"

		: "=&r" (contended), "=&r" (res)

		: "r" (&rw->lock)

		: "cc");

	} while (res);



	/* If the lock is negative, then it is already held for write. */

	if (contended < 0x80000000) {

		smp_mb();

	return tmp2 == 0;

		return 1;

	} else {

		return 0;

	}

}



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