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parisc: Remove unnecessary barriers from spinlock.h
commit 3b885ac1dc
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: John David Anglin <dave.anglin@bell.net>
Cc: stable@vger.kernel.org # 4.0+
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
parent
5962984873
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eba0611e98
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@ -26,7 +26,6 @@ static inline void arch_spin_lock_flags(arch_spinlock_t *x,
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{
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volatile unsigned int *a;
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mb();
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a = __ldcw_align(x);
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while (__ldcw(a) == 0)
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while (*a == 0)
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@ -36,16 +35,15 @@ static inline void arch_spin_lock_flags(arch_spinlock_t *x,
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local_irq_disable();
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} else
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cpu_relax();
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mb();
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}
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static inline void arch_spin_unlock(arch_spinlock_t *x)
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{
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volatile unsigned int *a;
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mb();
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a = __ldcw_align(x);
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*a = 1;
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mb();
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*a = 1;
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}
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static inline int arch_spin_trylock(arch_spinlock_t *x)
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@ -53,10 +51,8 @@ static inline int arch_spin_trylock(arch_spinlock_t *x)
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volatile unsigned int *a;
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int ret;
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mb();
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a = __ldcw_align(x);
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ret = __ldcw(a) != 0;
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mb();
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return ret;
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}
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