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arm64: percpu: Implement this_cpu operations
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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@linaro.org>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
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@stevecapperlinaro @wildea01
stevecapperlinaro authored and wildea01 committed Nov 20, 2014
1 parent 15670ef commit f97fc81
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Showing 2 changed files with 219 additions and 2 deletions.
6 changes: 4 additions & 2 deletions arch/arm64/include/asm/cmpxchg.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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)), \
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215 changes: 215 additions & 0 deletions arch/arm64/include/asm/percpu.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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 */

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