ARM: 7811/1: locks: use early clobber in arch_spin_trylock

commit afa31d8eb86fc2f25083e675d57ac8173a98f999 upstream.

The res variable is written before we've finished with the input
operands (namely the lock address), so ensure that we mark it as `early
clobber' to avoid unintended register sharing.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Wang Weidong <wangweidong1@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm/include/asm/spinlock.h b/arch/arm/include/asm/spinlock.h
index dd64cc6f9cbafd07e03d2bccbd7d201511a95e0d..b07c09e5a0ac86c6ddd5f7bc9ba25425c784e147 100644 (file)
--- a/arch/arm/include/asm/spinlock.h
+++ b/arch/arm/include/asm/spinlock.h
@@ -107,7 +107,7 @@ static inline int arch_spin_trylock(arch_spinlock_t *lock)
                "       subs    %1, %0, %0, ror #16\n"
                "       addeq   %0, %0, %4\n"
                "       strexeq %2, %0, [%3]"
-               : "=&r" (slock), "=&r" (contended), "=r" (res)
+               : "=&r" (slock), "=&r" (contended), "=&r" (res)
                : "r" (&lock->slock), "I" (1 << TICKET_SHIFT)
                : "cc");
        } while (res);