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Commit 15e7e5c1 authored by Will Deacon's avatar Will Deacon Committed by Russell King
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ARM: 7749/1: spinlock: retry trylock operation if strex fails on free lock 



An exclusive store instruction may fail for reasons other than lock
contention (e.g. a cache eviction during the critical section) so, in
line with other architectures using similar exclusive instructions
(alpha, mips, powerpc), retry the trylock operation if the lock appears
to be free but the strex reported failure.

Reported-by: default avatarTony Thompson <anthony.thompson@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 1aa2b3b7

arch/arm/include/asm/spinlock.h

+14 −11
Original line number Diff line number Diff line
@@ -97,19 +97,22 @@ static inline void arch_spin_lock(arch_spinlock_t *lock) 


static inline int arch_spin_trylock(arch_spinlock_t *lock)

{

	unsigned long tmp;

	unsigned long contended, res;

	u32 slock;



	do {

		__asm__ __volatile__(

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

		"	ldrex	%0, [%3]\n"

		"	mov	%2, #0\n"

		"	subs	%1, %0, %0, ror #16\n"

"	addeq	%0, %0, %3\n"

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

	: "=&r" (slock), "=&r" (tmp)

		"	addeq	%0, %0, %4\n"

		"	strexeq	%2, %0, [%3]"

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

		: "r" (&lock->slock), "I" (1 << TICKET_SHIFT)

		: "cc");

	} while (res);



	if (tmp == 0) {

	if (!contended) {

		smp_mb();

		return 1;

	} else {