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authorNicholas Piggin <npiggin@gmail.com>2016-09-22 11:55:54 -0400
committerTejun Heo <tj@kernel.org>2016-09-22 12:06:53 -0400
commit1b5ca12127427c51be605a75ecd0141eb3357249 (patch)
tree5181f24d2ff40d73916a9d7aba9b2315bd01ad21
parenta67823c1ed1092160da94c31e6da5aeb35dca81c (diff)
percpu: improve generic percpu modify-return implementation
Some architectures require an additional load to find the address of percpu pointers. In some implemenatations, the C aliasing rules do not allow the result of that load to be kept over the store that modifies the percpu variable, which causes additional loads. Work around this by finding the pointer first, then operating on that. It's also possible to mark things as restrict and those kind of games, but that can require larger and arch specific changes. On powerpc, __this_cpu_inc_return compiles to: ld 10,48(13) ldx 9,3,10 addi 9,9,1 stdx 9,3,10 ld 9,48(13) ldx 3,9,3 With this patch it compiles to: ld 10,48(13) ldx 9,3,10 addi 9,9,1 stdx 9,3,10 Signed-off-by: Nicholas Piggin <npiggin@gmail.com> To: Tejun Heo <tj@kernel.org> To: Christoph Lameter <cl@linux.com> Cc: linux-kernel@vger.kernel.org Cc: linux-arch@vger.kernel.org Signed-off-by: Tejun Heo <tj@kernel.org>
-rw-r--r--include/asm-generic/percpu.h53
1 files changed, 30 insertions, 23 deletions
diff --git a/include/asm-generic/percpu.h b/include/asm-generic/percpu.h
index 4d9f233c4ba8..40e887068da2 100644
--- a/include/asm-generic/percpu.h
+++ b/include/asm-generic/percpu.h
@@ -65,6 +65,11 @@ extern void setup_per_cpu_areas(void);
#define PER_CPU_DEF_ATTRIBUTES
#endif
+#define raw_cpu_generic_read(pcp) \
+({ \
+ *raw_cpu_ptr(&(pcp)); \
+})
+
#define raw_cpu_generic_to_op(pcp, val, op) \
do { \
*raw_cpu_ptr(&(pcp)) op val; \
@@ -72,34 +77,39 @@ do { \
#define raw_cpu_generic_add_return(pcp, val) \
({ \
- raw_cpu_add(pcp, val); \
- raw_cpu_read(pcp); \
+ typeof(&(pcp)) __p = raw_cpu_ptr(&(pcp)); \
+ \
+ *__p += val; \
+ *__p; \
})
#define raw_cpu_generic_xchg(pcp, nval) \
({ \
+ typeof(&(pcp)) __p = raw_cpu_ptr(&(pcp)); \
typeof(pcp) __ret; \
- __ret = raw_cpu_read(pcp); \
- raw_cpu_write(pcp, nval); \
+ __ret = *__p; \
+ *__p = nval; \
__ret; \
})
#define raw_cpu_generic_cmpxchg(pcp, oval, nval) \
({ \
+ typeof(&(pcp)) __p = raw_cpu_ptr(&(pcp)); \
typeof(pcp) __ret; \
- __ret = raw_cpu_read(pcp); \
+ __ret = *__p; \
if (__ret == (oval)) \
- raw_cpu_write(pcp, nval); \
+ *__p = nval; \
__ret; \
})
#define raw_cpu_generic_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \
({ \
+ typeof(&(pcp1)) __p1 = raw_cpu_ptr(&(pcp1)); \
+ typeof(&(pcp2)) __p2 = raw_cpu_ptr(&(pcp2)); \
int __ret = 0; \
- if (raw_cpu_read(pcp1) == (oval1) && \
- raw_cpu_read(pcp2) == (oval2)) { \
- raw_cpu_write(pcp1, nval1); \
- raw_cpu_write(pcp2, nval2); \
+ if (*__p1 == (oval1) && *__p2 == (oval2)) { \
+ *__p1 = nval1; \
+ *__p2 = nval2; \
__ret = 1; \
} \
(__ret); \
@@ -109,7 +119,7 @@ do { \
({ \
typeof(pcp) __ret; \
preempt_disable(); \
- __ret = *this_cpu_ptr(&(pcp)); \
+ __ret = raw_cpu_generic_read(pcp); \
preempt_enable(); \
__ret; \
})
@@ -118,17 +128,17 @@ do { \
do { \
unsigned long __flags; \
raw_local_irq_save(__flags); \
- *raw_cpu_ptr(&(pcp)) op val; \
+ raw_cpu_generic_to_op(pcp, val, op); \
raw_local_irq_restore(__flags); \
} while (0)
+
#define this_cpu_generic_add_return(pcp, val) \
({ \
typeof(pcp) __ret; \
unsigned long __flags; \
raw_local_irq_save(__flags); \
- raw_cpu_add(pcp, val); \
- __ret = raw_cpu_read(pcp); \
+ __ret = raw_cpu_generic_add_return(pcp, val); \
raw_local_irq_restore(__flags); \
__ret; \
})
@@ -138,8 +148,7 @@ do { \
typeof(pcp) __ret; \
unsigned long __flags; \
raw_local_irq_save(__flags); \
- __ret = raw_cpu_read(pcp); \
- raw_cpu_write(pcp, nval); \
+ __ret = raw_cpu_generic_xchg(pcp, nval); \
raw_local_irq_restore(__flags); \
__ret; \
})
@@ -149,9 +158,7 @@ do { \
typeof(pcp) __ret; \
unsigned long __flags; \
raw_local_irq_save(__flags); \
- __ret = raw_cpu_read(pcp); \
- if (__ret == (oval)) \
- raw_cpu_write(pcp, nval); \
+ __ret = raw_cpu_generic_cmpxchg(pcp, oval, nval); \
raw_local_irq_restore(__flags); \
__ret; \
})
@@ -168,16 +175,16 @@ do { \
})
#ifndef raw_cpu_read_1
-#define raw_cpu_read_1(pcp) (*raw_cpu_ptr(&(pcp)))
+#define raw_cpu_read_1(pcp) raw_cpu_generic_read(pcp)
#endif
#ifndef raw_cpu_read_2
-#define raw_cpu_read_2(pcp) (*raw_cpu_ptr(&(pcp)))
+#define raw_cpu_read_2(pcp) raw_cpu_generic_read(pcp)
#endif
#ifndef raw_cpu_read_4
-#define raw_cpu_read_4(pcp) (*raw_cpu_ptr(&(pcp)))
+#define raw_cpu_read_4(pcp) raw_cpu_generic_read(pcp)
#endif
#ifndef raw_cpu_read_8
-#define raw_cpu_read_8(pcp) (*raw_cpu_ptr(&(pcp)))
+#define raw_cpu_read_8(pcp) raw_cpu_generic_read(pcp)
#endif
#ifndef raw_cpu_write_1