[PATCH V4] arm64: percpu: Implement this_cpu operations
Steve Capper
steve.capper at linaro.org
Fri Nov 14 07:03:33 PST 2014
The generic this_cpu operations disable interrupts to ensure that the
requested operation is protected from pre-emption. For arm64, this is
overkill and can hurt throughput and latency.
This patch provides arm64 specific implementations for the this_cpu
operations. Rather than disable interrupts, we use the exclusive
monitor or atomic operations as appropriate.
The following operations are implemented: add, add_return, and, or,
read, write, xchg. We also wire up a cmpxchg implementation from
cmpxchg.h.
Testing was performed using the percpu_test module and hackbench on a
Juno board running 3.18-rc4.
Signed-off-by: Steve Capper <steve.capper at linaro.org>
---
Changed in V4: rebased to allow for merge in Will's for-next branch.
(I had erroneously changed my cmpxchg_double patch).
Changed the read/write accessors to use ACCESS_ONCE rather than asm.
Changed in V3: use cmpxchg_local rather than cmpxchg for
this_cpu_cmpxchg.
Changed in V2: corrected address constraint for __percpu_read and
__percpu_write.
---
arch/arm64/include/asm/cmpxchg.h | 6 +-
arch/arm64/include/asm/percpu.h | 215 +++++++++++++++++++++++++++++++++++++++
2 files changed, 219 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/include/asm/cmpxchg.h b/arch/arm64/include/asm/cmpxchg.h
index 89e397b..cb95930 100644
--- a/arch/arm64/include/asm/cmpxchg.h
+++ b/arch/arm64/include/asm/cmpxchg.h
@@ -246,8 +246,10 @@ static inline unsigned long __cmpxchg_mb(volatile void *ptr, unsigned long old,
__ret; \
})
-#define this_cpu_cmpxchg_8(ptr, o, n) \
- cmpxchg_local(raw_cpu_ptr(&(ptr)), o, n)
+#define this_cpu_cmpxchg_1(ptr, o, n) cmpxchg_local(raw_cpu_ptr(&(ptr)), o, n)
+#define this_cpu_cmpxchg_2(ptr, o, n) cmpxchg_local(raw_cpu_ptr(&(ptr)), o, n)
+#define this_cpu_cmpxchg_4(ptr, o, n) cmpxchg_local(raw_cpu_ptr(&(ptr)), o, n)
+#define this_cpu_cmpxchg_8(ptr, o, n) cmpxchg_local(raw_cpu_ptr(&(ptr)), o, n)
#define this_cpu_cmpxchg_double_8(ptr1, ptr2, o1, o2, n1, n2) \
cmpxchg_double_local(raw_cpu_ptr(&(ptr1)), raw_cpu_ptr(&(ptr2)), \
diff --git a/arch/arm64/include/asm/percpu.h b/arch/arm64/include/asm/percpu.h
index 5279e57..b8b2c8a 100644
--- a/arch/arm64/include/asm/percpu.h
+++ b/arch/arm64/include/asm/percpu.h
@@ -44,6 +44,221 @@ static inline unsigned long __my_cpu_offset(void)
#endif /* CONFIG_SMP */
+#define PERCPU_OP(op, asm_op) \
+static inline unsigned long __percpu_##op(void *ptr, \
+ unsigned long val, int size) \
+{ \
+ unsigned long loop, ret; \
+ \
+ switch (size) { \
+ case 1: \
+ do { \
+ asm ("//__per_cpu_" #op "_1\n" \
+ "ldxrb %w[ret], %[ptr]\n" \
+ #asm_op " %w[ret], %w[ret], %w[val]\n" \
+ "stxrb %w[loop], %w[ret], %[ptr]\n" \
+ : [loop] "=&r" (loop), [ret] "=&r" (ret), \
+ [ptr] "+Q"(*(u8 *)ptr) \
+ : [val] "Ir" (val)); \
+ } while (loop); \
+ break; \
+ case 2: \
+ do { \
+ asm ("//__per_cpu_" #op "_2\n" \
+ "ldxrh %w[ret], %[ptr]\n" \
+ #asm_op " %w[ret], %w[ret], %w[val]\n" \
+ "stxrh %w[loop], %w[ret], %[ptr]\n" \
+ : [loop] "=&r" (loop), [ret] "=&r" (ret), \
+ [ptr] "+Q"(*(u16 *)ptr) \
+ : [val] "Ir" (val)); \
+ } while (loop); \
+ break; \
+ case 4: \
+ do { \
+ asm ("//__per_cpu_" #op "_4\n" \
+ "ldxr %w[ret], %[ptr]\n" \
+ #asm_op " %w[ret], %w[ret], %w[val]\n" \
+ "stxr %w[loop], %w[ret], %[ptr]\n" \
+ : [loop] "=&r" (loop), [ret] "=&r" (ret), \
+ [ptr] "+Q"(*(u32 *)ptr) \
+ : [val] "Ir" (val)); \
+ } while (loop); \
+ break; \
+ case 8: \
+ do { \
+ asm ("//__per_cpu_" #op "_8\n" \
+ "ldxr %[ret], %[ptr]\n" \
+ #asm_op " %[ret], %[ret], %[val]\n" \
+ "stxr %w[loop], %[ret], %[ptr]\n" \
+ : [loop] "=&r" (loop), [ret] "=&r" (ret), \
+ [ptr] "+Q"(*(u64 *)ptr) \
+ : [val] "Ir" (val)); \
+ } while (loop); \
+ break; \
+ default: \
+ BUILD_BUG(); \
+ } \
+ \
+ return ret; \
+}
+
+PERCPU_OP(add, add)
+PERCPU_OP(and, and)
+PERCPU_OP(or, orr)
+#undef PERCPU_OP
+
+static inline unsigned long __percpu_read(void *ptr, int size)
+{
+ unsigned long ret;
+
+ switch (size) {
+ case 1:
+ ret = ACCESS_ONCE(*(u8 *)ptr);
+ break;
+ case 2:
+ ret = ACCESS_ONCE(*(u16 *)ptr);
+ break;
+ case 4:
+ ret = ACCESS_ONCE(*(u32 *)ptr);
+ break;
+ case 8:
+ ret = ACCESS_ONCE(*(u64 *)ptr);
+ break;
+ default:
+ BUILD_BUG();
+ }
+
+ return ret;
+}
+
+static inline void __percpu_write(void *ptr, unsigned long val, int size)
+{
+ switch (size) {
+ case 1:
+ ACCESS_ONCE(*((u8 *)ptr)) = (u8) val;
+ break;
+ case 2:
+ ACCESS_ONCE(*((u16 *)ptr)) = (u16) val;
+ break;
+ case 4:
+ ACCESS_ONCE(*((u32 *)ptr)) = (u32) val;
+ break;
+ case 8:
+ ACCESS_ONCE(*((u64 *)ptr)) = (u64) val;
+ break;
+ default:
+ BUILD_BUG();
+ }
+}
+
+static inline unsigned long __percpu_xchg(void *ptr, unsigned long val,
+ int size)
+{
+ unsigned long ret, loop;
+
+ switch (size) {
+ case 1:
+ do {
+ asm ("//__percpu_xchg_1\n"
+ "ldxrb %w[ret], %[ptr]\n"
+ "stxrb %w[loop], %w[val], %[ptr]\n"
+ : [loop] "=&r"(loop), [ret] "=&r"(ret),
+ [ptr] "+Q"(*(u8 *)ptr)
+ : [val] "r" (val));
+ } while (loop);
+ break;
+ case 2:
+ do {
+ asm ("//__percpu_xchg_2\n"
+ "ldxrh %w[ret], %[ptr]\n"
+ "stxrh %w[loop], %w[val], %[ptr]\n"
+ : [loop] "=&r"(loop), [ret] "=&r"(ret),
+ [ptr] "+Q"(*(u16 *)ptr)
+ : [val] "r" (val));
+ } while (loop);
+ break;
+ case 4:
+ do {
+ asm ("//__percpu_xchg_4\n"
+ "ldxr %w[ret], %[ptr]\n"
+ "stxr %w[loop], %w[val], %[ptr]\n"
+ : [loop] "=&r"(loop), [ret] "=&r"(ret),
+ [ptr] "+Q"(*(u32 *)ptr)
+ : [val] "r" (val));
+ } while (loop);
+ break;
+ case 8:
+ do {
+ asm ("//__percpu_xchg_8\n"
+ "ldxr %[ret], %[ptr]\n"
+ "stxr %w[loop], %[val], %[ptr]\n"
+ : [loop] "=&r"(loop), [ret] "=&r"(ret),
+ [ptr] "+Q"(*(u64 *)ptr)
+ : [val] "r" (val));
+ } while (loop);
+ break;
+ default:
+ BUILD_BUG();
+ }
+
+ return ret;
+}
+
+#define _percpu_add(pcp, val) \
+ __percpu_add(raw_cpu_ptr(&(pcp)), val, sizeof(pcp))
+
+#define _percpu_add_return(pcp, val) (typeof(pcp)) (_percpu_add(pcp, val))
+
+#define _percpu_and(pcp, val) \
+ __percpu_and(raw_cpu_ptr(&(pcp)), val, sizeof(pcp))
+
+#define _percpu_or(pcp, val) \
+ __percpu_or(raw_cpu_ptr(&(pcp)), val, sizeof(pcp))
+
+#define _percpu_read(pcp) (typeof(pcp)) \
+ (__percpu_read(raw_cpu_ptr(&(pcp)), sizeof(pcp)))
+
+#define _percpu_write(pcp, val) \
+ __percpu_write(raw_cpu_ptr(&(pcp)), (unsigned long)(val), sizeof(pcp))
+
+#define _percpu_xchg(pcp, val) (typeof(pcp)) \
+ (__percpu_xchg(raw_cpu_ptr(&(pcp)), (unsigned long)(val), sizeof(pcp)))
+
+#define this_cpu_add_1(pcp, val) _percpu_add(pcp, val)
+#define this_cpu_add_2(pcp, val) _percpu_add(pcp, val)
+#define this_cpu_add_4(pcp, val) _percpu_add(pcp, val)
+#define this_cpu_add_8(pcp, val) _percpu_add(pcp, val)
+
+#define this_cpu_add_return_1(pcp, val) _percpu_add_return(pcp, val)
+#define this_cpu_add_return_2(pcp, val) _percpu_add_return(pcp, val)
+#define this_cpu_add_return_4(pcp, val) _percpu_add_return(pcp, val)
+#define this_cpu_add_return_8(pcp, val) _percpu_add_return(pcp, val)
+
+#define this_cpu_and_1(pcp, val) _percpu_and(pcp, val)
+#define this_cpu_and_2(pcp, val) _percpu_and(pcp, val)
+#define this_cpu_and_4(pcp, val) _percpu_and(pcp, val)
+#define this_cpu_and_8(pcp, val) _percpu_and(pcp, val)
+
+#define this_cpu_or_1(pcp, val) _percpu_or(pcp, val)
+#define this_cpu_or_2(pcp, val) _percpu_or(pcp, val)
+#define this_cpu_or_4(pcp, val) _percpu_or(pcp, val)
+#define this_cpu_or_8(pcp, val) _percpu_or(pcp, val)
+
+#define this_cpu_read_1(pcp) _percpu_read(pcp)
+#define this_cpu_read_2(pcp) _percpu_read(pcp)
+#define this_cpu_read_4(pcp) _percpu_read(pcp)
+#define this_cpu_read_8(pcp) _percpu_read(pcp)
+
+#define this_cpu_write_1(pcp, val) _percpu_write(pcp, val)
+#define this_cpu_write_2(pcp, val) _percpu_write(pcp, val)
+#define this_cpu_write_4(pcp, val) _percpu_write(pcp, val)
+#define this_cpu_write_8(pcp, val) _percpu_write(pcp, val)
+
+#define this_cpu_xchg_1(pcp, val) _percpu_xchg(pcp, val)
+#define this_cpu_xchg_2(pcp, val) _percpu_xchg(pcp, val)
+#define this_cpu_xchg_4(pcp, val) _percpu_xchg(pcp, val)
+#define this_cpu_xchg_8(pcp, val) _percpu_xchg(pcp, val)
+
#include <asm-generic/percpu.h>
#endif /* __ASM_PERCPU_H */
--
1.9.3
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