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| author | John David Anglin <dave.anglin@bell.net> | 2018-08-12 16:31:17 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-08-24 13:07:15 +0200 |
| commit | 5c9fc580b1bc23eb8a23fddbd67e82c29d2aadfe (patch) | |
| tree | e5b28a909d5faaf82bd1397d3bd44de3431ea6c7 | |
| parent | 4027d547d60121602404873c92c673d18ce7af7d (diff) | |
| download | linux-stable-5c9fc580b1bc23eb8a23fddbd67e82c29d2aadfe.tar.gz linux-stable-5c9fc580b1bc23eb8a23fddbd67e82c29d2aadfe.tar.bz2 linux-stable-5c9fc580b1bc23eb8a23fddbd67e82c29d2aadfe.zip | |
parisc: Remove unnecessary barriers from spinlock.h
commit 3b885ac1dc35b87a39ee176a6c7e2af9c789d8b8 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>
| -rw-r--r-- | arch/parisc/include/asm/spinlock.h | 8 |
1 files changed, 2 insertions, 6 deletions
diff --git a/arch/parisc/include/asm/spinlock.h b/arch/parisc/include/asm/spinlock.h index 6f84b6acc86e..8a63515f03bf 100644 --- a/arch/parisc/include/asm/spinlock.h +++ b/arch/parisc/include/asm/spinlock.h @@ -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; } |