Commit e1d35a1a authored by John David Anglin's avatar John David Anglin Committed by Greg Kroah-Hartman
Browse files

parisc: Remove unnecessary barriers from spinlock.h

commit 3b885ac1

 upstream.

Now that mb() is an instruction barrier, it will slow performance if we issue
unnecessary barriers.

The spinlock defines have a number of unnecessary barriers.  The __ldcw()
define is both a hardware and compiler barrier.  The mb() barriers in the
routines using __ldcw() serve no purpose.

The only barrier needed is the one in arch_spin_unlock().  We need to ensure
all accesses are complete prior to releasing the lock.
Signed-off-by: default avatarJohn David Anglin <dave.anglin@bell.net>
Cc: stable@vger.kernel.org # 4.0+
Signed-off-by: default avatarHelge Deller <deller@gmx.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 3df731e0
......@@ -20,7 +20,6 @@ static inline void arch_spin_lock_flags(arch_spinlock_t *x,
{
volatile unsigned int *a;
mb();
a = __ldcw_align(x);
while (__ldcw(a) == 0)
while (*a == 0)
......@@ -30,17 +29,16 @@ static inline void arch_spin_lock_flags(arch_spinlock_t *x,
local_irq_disable();
} else
cpu_relax();
mb();
}
#define arch_spin_lock_flags arch_spin_lock_flags
static inline void arch_spin_unlock(arch_spinlock_t *x)
{
volatile unsigned int *a;
mb();
a = __ldcw_align(x);
*a = 1;
mb();
*a = 1;
}
static inline int arch_spin_trylock(arch_spinlock_t *x)
......@@ -48,10 +46,8 @@ static inline int arch_spin_trylock(arch_spinlock_t *x)
volatile unsigned int *a;
int ret;
mb();
a = __ldcw_align(x);
ret = __ldcw(a) != 0;
mb();
return ret;
}
......
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