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Kernel
提交 959bf2fd 编写于 作者: W Will Deacon
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arm64: percpu: Rewrite per-cpu ops to allow use of LSE atomics 

Our percpu code is a bit of an inconsistent mess:

  * It rolls its own xchg(), but reuses cmpxchg_local()
  * It uses various different flavours of preempt_{enable,disable}()
  * It returns values even for the non-returning RmW operations
  * It makes no use of LSE atomics outside of the cmpxchg() ops
  * There are individual macros for different sizes of access, but these
    are all funneled through a switch statement rather than dispatched
    directly to the relevant case

This patch rewrites the per-cpu operations to address these shortcomings.
Whilst the new code is a lot cleaner, the big advantage is that we can
use the non-returning ST- atomic instructions when we have LSE.
Signed-off-by: NWill Deacon <will.deacon@arm.com>
上级 b4f9209b
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arch/arm64/include/asm/percpu.h
浏览文件 @ 959bf2fd
...@@ -48,263 +48,193 @@ static inline unsigned long __my_cpu_offset(void) ...@@ -48,263 +48,193 @@ static inline unsigned long __my_cpu_offset(void)
} }
#define __my_cpu_offset __my_cpu_offset() #define __my_cpu_offset __my_cpu_offset()
#define PERCPU_OP(op, asm_op) \ #define PERCPU_RW_OPS(sz) \
static inline unsigned long __percpu_##op(void *ptr, \ static inline unsigned long __percpu_read_##sz(void *ptr) \
unsigned long val, int size) \
{ \ { \
unsigned long loop, ret; \ return READ_ONCE(*(u##sz *)ptr); \
} \
\ \
switch (size) { \ static inline void __percpu_write_##sz(void *ptr, unsigned long val) \
case 1: \ { \
asm ("//__per_cpu_" #op "_1\n" \ WRITE_ONCE(*(u##sz *)ptr, (u##sz)val); \
"1: ldxrb %w[ret], %[ptr]\n" \
#asm_op " %w[ret], %w[ret], %w[val]\n" \
" stxrb %w[loop], %w[ret], %[ptr]\n" \
" cbnz %w[loop], 1b" \
: [loop] "=&r" (loop), [ret] "=&r" (ret), \
[ptr] "+Q"(*(u8 *)ptr) \
: [val] "Ir" (val)); \
break; \
case 2: \
asm ("//__per_cpu_" #op "_2\n" \
"1: ldxrh %w[ret], %[ptr]\n" \
#asm_op " %w[ret], %w[ret], %w[val]\n" \
" stxrh %w[loop], %w[ret], %[ptr]\n" \
" cbnz %w[loop], 1b" \
: [loop] "=&r" (loop), [ret] "=&r" (ret), \
[ptr] "+Q"(*(u16 *)ptr) \
: [val] "Ir" (val)); \
break; \
case 4: \
asm ("//__per_cpu_" #op "_4\n" \
"1: ldxr %w[ret], %[ptr]\n" \
#asm_op " %w[ret], %w[ret], %w[val]\n" \
" stxr %w[loop], %w[ret], %[ptr]\n" \
" cbnz %w[loop], 1b" \
: [loop] "=&r" (loop), [ret] "=&r" (ret), \
[ptr] "+Q"(*(u32 *)ptr) \
: [val] "Ir" (val)); \
break; \
case 8: \
asm ("//__per_cpu_" #op "_8\n" \
"1: ldxr %[ret], %[ptr]\n" \
#asm_op " %[ret], %[ret], %[val]\n" \
" stxr %w[loop], %[ret], %[ptr]\n" \
" cbnz %w[loop], 1b" \
: [loop] "=&r" (loop), [ret] "=&r" (ret), \
[ptr] "+Q"(*(u64 *)ptr) \
: [val] "Ir" (val)); \
break; \
default: \
ret = 0; \
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 = READ_ONCE(*(u8 *)ptr);
break;
case 2:
ret = READ_ONCE(*(u16 *)ptr);
break;
case 4:
ret = READ_ONCE(*(u32 *)ptr);
break;
case 8:
ret = READ_ONCE(*(u64 *)ptr);
break;
default:
ret = 0;
BUILD_BUG();
}
return ret;
} }
static inline void __percpu_write(void *ptr, unsigned long val, int size) #define __PERCPU_OP_CASE(w, sfx, name, sz, op_llsc, op_lse) \
{ static inline void \
switch (size) { __percpu_##name##_case_##sz(void *ptr, unsigned long val) \
case 1: { \
WRITE_ONCE(*(u8 *)ptr, (u8)val); unsigned int loop; \
break; u##sz tmp; \
case 2: \
WRITE_ONCE(*(u16 *)ptr, (u16)val); asm volatile (ARM64_LSE_ATOMIC_INSN( \
break; /* LL/SC */ \
case 4: "1: ldxr" #sfx "\t%" #w "[tmp], %[ptr]\n" \
WRITE_ONCE(*(u32 *)ptr, (u32)val); #op_llsc "\t%" #w "[tmp], %" #w "[tmp], %" #w "[val]\n" \
break; " stxr" #sfx "\t%w[loop], %" #w "[tmp], %[ptr]\n" \
case 8: " cbnz %w[loop], 1b", \
WRITE_ONCE(*(u64 *)ptr, (u64)val); /* LSE atomics */ \
break; #op_lse "\t%" #w "[val], %[ptr]\n" \
default: __nops(3)) \
BUILD_BUG(); : [loop] "=&r" (loop), [tmp] "=&r" (tmp), \
} [ptr] "+Q"(*(u##sz *)ptr) \
: [val] "r" ((u##sz)(val))); \
} }
static inline unsigned long __percpu_xchg(void *ptr, unsigned long val, #define __PERCPU_RET_OP_CASE(w, sfx, name, sz, op_llsc, op_lse) \
int size) static inline u##sz \
{ __percpu_##name##_return_case_##sz(void *ptr, unsigned long val) \
unsigned long ret, loop; { \
unsigned int loop; \
switch (size) { u##sz ret; \
case 1: \
asm ("//__percpu_xchg_1\n" asm volatile (ARM64_LSE_ATOMIC_INSN( \
"1: ldxrb %w[ret], %[ptr]\n" /* LL/SC */ \
" stxrb %w[loop], %w[val], %[ptr]\n" "1: ldxr" #sfx "\t%" #w "[ret], %[ptr]\n" \
" cbnz %w[loop], 1b" #op_llsc "\t%" #w "[ret], %" #w "[ret], %" #w "[val]\n" \
: [loop] "=&r"(loop), [ret] "=&r"(ret), " stxr" #sfx "\t%w[loop], %" #w "[ret], %[ptr]\n" \
[ptr] "+Q"(*(u8 *)ptr) " cbnz %w[loop], 1b", \
: [val] "r" (val)); /* LSE atomics */ \
break; #op_lse "\t%" #w "[ret], %" #w "[val], %[ptr]\n" \
case 2: #op_llsc "\t%" #w "[ret], %" #w "[ret], %" #w "[val]\n" \
asm ("//__percpu_xchg_2\n" __nops(2)) \
"1: ldxrh %w[ret], %[ptr]\n" : [loop] "=&r" (loop), [ret] "=&r" (ret), \
" stxrh %w[loop], %w[val], %[ptr]\n" [ptr] "+Q"(*(u##sz *)ptr) \
" cbnz %w[loop], 1b" : [val] "r" ((u##sz)(val))); \
: [loop] "=&r"(loop), [ret] "=&r"(ret), \
[ptr] "+Q"(*(u16 *)ptr) return ret; \
: [val] "r" (val));
break;
case 4:
asm ("//__percpu_xchg_4\n"
"1: ldxr %w[ret], %[ptr]\n"
" stxr %w[loop], %w[val], %[ptr]\n"
" cbnz %w[loop], 1b"
: [loop] "=&r"(loop), [ret] "=&r"(ret),
[ptr] "+Q"(*(u32 *)ptr)
: [val] "r" (val));
break;
case 8:
asm ("//__percpu_xchg_8\n"
"1: ldxr %[ret], %[ptr]\n"
" stxr %w[loop], %[val], %[ptr]\n"
" cbnz %w[loop], 1b"
: [loop] "=&r"(loop), [ret] "=&r"(ret),
[ptr] "+Q"(*(u64 *)ptr)
: [val] "r" (val));
break;
default:
ret = 0;
BUILD_BUG();
}
return ret;
} }
/* this_cpu_cmpxchg */ #define PERCPU_OP(name, op_llsc, op_lse) \
#define _protect_cmpxchg_local(pcp, o, n) \ __PERCPU_OP_CASE(w, b, name, 8, op_llsc, op_lse) \
({ \ __PERCPU_OP_CASE(w, h, name, 16, op_llsc, op_lse) \
typeof(*raw_cpu_ptr(&(pcp))) __ret; \ __PERCPU_OP_CASE(w, , name, 32, op_llsc, op_lse) \
preempt_disable(); \ __PERCPU_OP_CASE( , , name, 64, op_llsc, op_lse)
__ret = cmpxchg_local(raw_cpu_ptr(&(pcp)), o, n); \
preempt_enable(); \ #define PERCPU_RET_OP(name, op_llsc, op_lse) \
__ret; \ __PERCPU_RET_OP_CASE(w, b, name, 8, op_llsc, op_lse) \
}) __PERCPU_RET_OP_CASE(w, h, name, 16, op_llsc, op_lse) \
__PERCPU_RET_OP_CASE(w, , name, 32, op_llsc, op_lse) \
#define this_cpu_cmpxchg_1(ptr, o, n) _protect_cmpxchg_local(ptr, o, n) __PERCPU_RET_OP_CASE( , , name, 64, op_llsc, op_lse)
#define this_cpu_cmpxchg_2(ptr, o, n) _protect_cmpxchg_local(ptr, o, n)
#define this_cpu_cmpxchg_4(ptr, o, n) _protect_cmpxchg_local(ptr, o, n) PERCPU_RW_OPS(8)
#define this_cpu_cmpxchg_8(ptr, o, n) _protect_cmpxchg_local(ptr, o, n) PERCPU_RW_OPS(16)
PERCPU_RW_OPS(32)
PERCPU_RW_OPS(64)
PERCPU_OP(add, add, stadd)
PERCPU_OP(andnot, bic, stclr)
PERCPU_OP(or, orr, stset)
PERCPU_RET_OP(add, add, ldadd)
#undef PERCPU_RW_OPS
#undef __PERCPU_OP_CASE
#undef __PERCPU_RET_OP_CASE
#undef PERCPU_OP
#undef PERCPU_RET_OP
/*
* It would be nice to avoid the conditional call into the scheduler when
* re-enabling preemption for preemptible kernels, but doing that in a way
* which builds inside a module would mean messing directly with the preempt
* count. If you do this, peterz and tglx will hunt you down.
*/
#define this_cpu_cmpxchg_double_8(ptr1, ptr2, o1, o2, n1, n2) \ #define this_cpu_cmpxchg_double_8(ptr1, ptr2, o1, o2, n1, n2) \
({ \ ({ \
int __ret; \ int __ret; \
preempt_disable(); \ preempt_disable_notrace(); \
__ret = cmpxchg_double_local( raw_cpu_ptr(&(ptr1)), \ __ret = cmpxchg_double_local( raw_cpu_ptr(&(ptr1)), \
raw_cpu_ptr(&(ptr2)), \ raw_cpu_ptr(&(ptr2)), \
o1, o2, n1, n2); \ o1, o2, n1, n2); \
preempt_enable(); \ preempt_enable_notrace(); \
__ret; \ __ret; \
}) })
#define _percpu_read(pcp) \ #define _pcp_protect(op, pcp, ...) \
({ \ ({ \
typeof(pcp) __retval; \
preempt_disable_notrace(); \ preempt_disable_notrace(); \
__retval = (typeof(pcp))__percpu_read(raw_cpu_ptr(&(pcp)), \ op(raw_cpu_ptr(&(pcp)), __VA_ARGS__); \
sizeof(pcp)); \
preempt_enable_notrace(); \ preempt_enable_notrace(); \
__retval; \
}) })
#define _percpu_write(pcp, val) \ #define _pcp_protect_return(op, pcp, args...) \
do { \ ({ \
typeof(pcp) __retval; \
preempt_disable_notrace(); \ preempt_disable_notrace(); \
__percpu_write(raw_cpu_ptr(&(pcp)), (unsigned long)(val), \ __retval = (typeof(pcp))op(raw_cpu_ptr(&(pcp)), ##args); \
sizeof(pcp)); \
preempt_enable_notrace(); \ preempt_enable_notrace(); \
} while(0) \ __retval; \
#define _pcp_protect(operation, pcp, val) \
({ \
typeof(pcp) __retval; \
preempt_disable(); \
__retval = (typeof(pcp))operation(raw_cpu_ptr(&(pcp)), \
(val), sizeof(pcp)); \
preempt_enable(); \
__retval; \
}) })
#define _percpu_add(pcp, val) \ #define this_cpu_read_1(pcp) \
_pcp_protect(__percpu_add, pcp, val) _pcp_protect_return(__percpu_read_8, pcp)
#define this_cpu_read_2(pcp) \
#define _percpu_add_return(pcp, val) _percpu_add(pcp, val) _pcp_protect_return(__percpu_read_16, pcp)
#define this_cpu_read_4(pcp) \
#define _percpu_and(pcp, val) \ _pcp_protect_return(__percpu_read_32, pcp)
_pcp_protect(__percpu_and, pcp, val) #define this_cpu_read_8(pcp) \
_pcp_protect_return(__percpu_read_64, pcp)
#define _percpu_or(pcp, val) \
_pcp_protect(__percpu_or, pcp, val) #define this_cpu_write_1(pcp, val) \
_pcp_protect(__percpu_write_8, pcp, (unsigned long)val)
#define _percpu_xchg(pcp, val) (typeof(pcp)) \ #define this_cpu_write_2(pcp, val) \
_pcp_protect(__percpu_xchg, pcp, (unsigned long)(val)) _pcp_protect(__percpu_write_16, pcp, (unsigned long)val)
#define this_cpu_write_4(pcp, val) \
#define this_cpu_add_1(pcp, val) _percpu_add(pcp, val) _pcp_protect(__percpu_write_32, pcp, (unsigned long)val)
#define this_cpu_add_2(pcp, val) _percpu_add(pcp, val) #define this_cpu_write_8(pcp, val) \
#define this_cpu_add_4(pcp, val) _percpu_add(pcp, val) _pcp_protect(__percpu_write_64, pcp, (unsigned long)val)
#define this_cpu_add_8(pcp, val) _percpu_add(pcp, val)
#define this_cpu_add_1(pcp, val) \
#define this_cpu_add_return_1(pcp, val) _percpu_add_return(pcp, val) _pcp_protect(__percpu_add_case_8, pcp, val)
#define this_cpu_add_return_2(pcp, val) _percpu_add_return(pcp, val) #define this_cpu_add_2(pcp, val) \
#define this_cpu_add_return_4(pcp, val) _percpu_add_return(pcp, val) _pcp_protect(__percpu_add_case_16, pcp, val)
#define this_cpu_add_return_8(pcp, val) _percpu_add_return(pcp, val) #define this_cpu_add_4(pcp, val) \
_pcp_protect(__percpu_add_case_32, pcp, val)
#define this_cpu_and_1(pcp, val) _percpu_and(pcp, val) #define this_cpu_add_8(pcp, val) \
#define this_cpu_and_2(pcp, val) _percpu_and(pcp, val) _pcp_protect(__percpu_add_case_64, 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_add_return_1(pcp, val) \
_pcp_protect_return(__percpu_add_return_case_8, pcp, val)
#define this_cpu_or_1(pcp, val) _percpu_or(pcp, val) #define this_cpu_add_return_2(pcp, val) \
#define this_cpu_or_2(pcp, val) _percpu_or(pcp, val) _pcp_protect_return(__percpu_add_return_case_16, pcp, val)
#define this_cpu_or_4(pcp, val) _percpu_or(pcp, val) #define this_cpu_add_return_4(pcp, val) \
#define this_cpu_or_8(pcp, val) _percpu_or(pcp, val) _pcp_protect_return(__percpu_add_return_case_32, pcp, val)
#define this_cpu_add_return_8(pcp, val) \
#define this_cpu_read_1(pcp) _percpu_read(pcp) _pcp_protect_return(__percpu_add_return_case_64, pcp, val)
#define this_cpu_read_2(pcp) _percpu_read(pcp)
#define this_cpu_read_4(pcp) _percpu_read(pcp) #define this_cpu_and_1(pcp, val) \
#define this_cpu_read_8(pcp) _percpu_read(pcp) _pcp_protect(__percpu_andnot_case_8, pcp, ~val)
#define this_cpu_and_2(pcp, val) \
#define this_cpu_write_1(pcp, val) _percpu_write(pcp, val) _pcp_protect(__percpu_andnot_case_16, pcp, ~val)
#define this_cpu_write_2(pcp, val) _percpu_write(pcp, val) #define this_cpu_and_4(pcp, val) \
#define this_cpu_write_4(pcp, val) _percpu_write(pcp, val) _pcp_protect(__percpu_andnot_case_32, pcp, ~val)
#define this_cpu_write_8(pcp, val) _percpu_write(pcp, val) #define this_cpu_and_8(pcp, val) \
_pcp_protect(__percpu_andnot_case_64, 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_or_1(pcp, val) \
#define this_cpu_xchg_4(pcp, val) _percpu_xchg(pcp, val) _pcp_protect(__percpu_or_case_8, pcp, val)
#define this_cpu_xchg_8(pcp, val) _percpu_xchg(pcp, val) #define this_cpu_or_2(pcp, val) \
_pcp_protect(__percpu_or_case_16, pcp, val)
#define this_cpu_or_4(pcp, val) \
_pcp_protect(__percpu_or_case_32, pcp, val)
#define this_cpu_or_8(pcp, val) \
_pcp_protect(__percpu_or_case_64, pcp, val)
#define this_cpu_xchg_1(pcp, val) \
_pcp_protect_return(xchg_relaxed, pcp, val)
#define this_cpu_xchg_2(pcp, val) \
_pcp_protect_return(xchg_relaxed, pcp, val)
#define this_cpu_xchg_4(pcp, val) \
_pcp_protect_return(xchg_relaxed, pcp, val)
#define this_cpu_xchg_8(pcp, val) \
_pcp_protect_return(xchg_relaxed, pcp, val)
#define this_cpu_cmpxchg_1(pcp, o, n) \
_pcp_protect_return(cmpxchg_relaxed, pcp, o, n)
#define this_cpu_cmpxchg_2(pcp, o, n) \
_pcp_protect_return(cmpxchg_relaxed, pcp, o, n)
#define this_cpu_cmpxchg_4(pcp, o, n) \
_pcp_protect_return(cmpxchg_relaxed, pcp, o, n)
#define this_cpu_cmpxchg_8(pcp, o, n) \
_pcp_protect_return(cmpxchg_relaxed, pcp, o, n)
#include <asm-generic/percpu.h> #include <asm-generic/percpu.h>
......
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