6dbde35308
It is an optimization and a cleanup, and adds the following new
generic percpu methods:
percpu_read()
percpu_write()
percpu_add()
percpu_sub()
percpu_and()
percpu_or()
percpu_xor()
and implements support for them on x86. (other architectures will fall
back to a default implementation)
The advantage is that for example to read a local percpu variable,
instead of this sequence:
return __get_cpu_var(var);
ffffffff8102ca2b: 48 8b 14 fd 80 09 74 mov -0x7e8bf680(,%rdi,8),%rdx
ffffffff8102ca32: 81
ffffffff8102ca33: 48 c7 c0 d8 59 00 00 mov $0x59d8,%rax
ffffffff8102ca3a: 48 8b 04 10 mov (%rax,%rdx,1),%rax
We can get a single instruction by using the optimized variants:
return percpu_read(var);
ffffffff8102ca3f: 65 48 8b 05 91 8f fd mov %gs:0x7efd8f91(%rip),%rax
I also cleaned up the x86-specific APIs and made the x86 code use
these new generic percpu primitives.
tj: * fixed generic percpu_sub() definition as Roel Kluin pointed out
* added percpu_and() for completeness's sake
* made generic percpu ops atomic against preemption
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Tejun Heo <tj@kernel.org>
190 lines
5.0 KiB
C
190 lines
5.0 KiB
C
#ifndef _ASM_X86_PERCPU_H
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#define _ASM_X86_PERCPU_H
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#ifdef CONFIG_X86_64
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#define __percpu_seg gs
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#define __percpu_mov_op movq
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#else
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#define __percpu_seg fs
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#define __percpu_mov_op movl
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#endif
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#ifdef __ASSEMBLY__
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/*
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* PER_CPU finds an address of a per-cpu variable.
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*
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* Args:
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* var - variable name
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* reg - 32bit register
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*
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* The resulting address is stored in the "reg" argument.
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*
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* Example:
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* PER_CPU(cpu_gdt_descr, %ebx)
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*/
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#ifdef CONFIG_SMP
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#define PER_CPU(var, reg) \
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__percpu_mov_op %__percpu_seg:per_cpu__this_cpu_off, reg; \
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lea per_cpu__##var(reg), reg
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#define PER_CPU_VAR(var) %__percpu_seg:per_cpu__##var
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#else /* ! SMP */
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#define PER_CPU(var, reg) \
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__percpu_mov_op $per_cpu__##var, reg
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#define PER_CPU_VAR(var) per_cpu__##var
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#endif /* SMP */
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#else /* ...!ASSEMBLY */
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#include <linux/stringify.h>
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#ifdef CONFIG_SMP
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#define __percpu_seg_str "%%"__stringify(__percpu_seg)":"
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#define __my_cpu_offset percpu_read(this_cpu_off)
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#else
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#define __percpu_seg_str
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#endif
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/* For arch-specific code, we can use direct single-insn ops (they
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* don't give an lvalue though). */
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extern void __bad_percpu_size(void);
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#define percpu_to_op(op, var, val) \
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do { \
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typedef typeof(var) T__; \
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if (0) { \
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T__ tmp__; \
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tmp__ = (val); \
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} \
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switch (sizeof(var)) { \
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case 1: \
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asm(op "b %1,"__percpu_seg_str"%0" \
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: "+m" (var) \
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: "ri" ((T__)val)); \
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break; \
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case 2: \
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asm(op "w %1,"__percpu_seg_str"%0" \
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: "+m" (var) \
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: "ri" ((T__)val)); \
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break; \
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case 4: \
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asm(op "l %1,"__percpu_seg_str"%0" \
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: "+m" (var) \
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: "ri" ((T__)val)); \
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break; \
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case 8: \
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asm(op "q %1,"__percpu_seg_str"%0" \
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: "+m" (var) \
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: "r" ((T__)val)); \
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break; \
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default: __bad_percpu_size(); \
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} \
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} while (0)
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#define percpu_from_op(op, var) \
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({ \
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typeof(var) ret__; \
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switch (sizeof(var)) { \
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case 1: \
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asm(op "b "__percpu_seg_str"%1,%0" \
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: "=r" (ret__) \
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: "m" (var)); \
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break; \
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case 2: \
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asm(op "w "__percpu_seg_str"%1,%0" \
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: "=r" (ret__) \
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: "m" (var)); \
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break; \
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case 4: \
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asm(op "l "__percpu_seg_str"%1,%0" \
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: "=r" (ret__) \
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: "m" (var)); \
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break; \
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case 8: \
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asm(op "q "__percpu_seg_str"%1,%0" \
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: "=r" (ret__) \
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: "m" (var)); \
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break; \
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default: __bad_percpu_size(); \
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} \
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ret__; \
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})
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#define percpu_read(var) percpu_from_op("mov", per_cpu__##var)
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#define percpu_write(var, val) percpu_to_op("mov", per_cpu__##var, val)
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#define percpu_add(var, val) percpu_to_op("add", per_cpu__##var, val)
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#define percpu_sub(var, val) percpu_to_op("sub", per_cpu__##var, val)
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#define percpu_and(var, val) percpu_to_op("and", per_cpu__##var, val)
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#define percpu_or(var, val) percpu_to_op("or", per_cpu__##var, val)
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#define percpu_xor(var, val) percpu_to_op("xor", per_cpu__##var, val)
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/* This is not atomic against other CPUs -- CPU preemption needs to be off */
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#define x86_test_and_clear_bit_percpu(bit, var) \
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({ \
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int old__; \
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asm volatile("btr %1,"__percpu_seg_str"%c2\n\tsbbl %0,%0" \
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: "=r" (old__) \
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: "dIr" (bit), "i" (&per_cpu__##var) : "memory"); \
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old__; \
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})
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#include <asm-generic/percpu.h>
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/* We can use this directly for local CPU (faster). */
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DECLARE_PER_CPU(unsigned long, this_cpu_off);
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#ifdef CONFIG_X86_64
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extern void load_pda_offset(int cpu);
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#else
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static inline void load_pda_offset(int cpu) { }
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#endif
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#endif /* !__ASSEMBLY__ */
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#ifdef CONFIG_SMP
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/*
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* Define the "EARLY_PER_CPU" macros. These are used for some per_cpu
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* variables that are initialized and accessed before there are per_cpu
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* areas allocated.
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*/
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#define DEFINE_EARLY_PER_CPU(_type, _name, _initvalue) \
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DEFINE_PER_CPU(_type, _name) = _initvalue; \
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__typeof__(_type) _name##_early_map[NR_CPUS] __initdata = \
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{ [0 ... NR_CPUS-1] = _initvalue }; \
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__typeof__(_type) *_name##_early_ptr __refdata = _name##_early_map
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#define EXPORT_EARLY_PER_CPU_SYMBOL(_name) \
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EXPORT_PER_CPU_SYMBOL(_name)
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#define DECLARE_EARLY_PER_CPU(_type, _name) \
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DECLARE_PER_CPU(_type, _name); \
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extern __typeof__(_type) *_name##_early_ptr; \
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extern __typeof__(_type) _name##_early_map[]
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#define early_per_cpu_ptr(_name) (_name##_early_ptr)
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#define early_per_cpu_map(_name, _idx) (_name##_early_map[_idx])
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#define early_per_cpu(_name, _cpu) \
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*(early_per_cpu_ptr(_name) ? \
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&early_per_cpu_ptr(_name)[_cpu] : \
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&per_cpu(_name, _cpu))
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#else /* !CONFIG_SMP */
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#define DEFINE_EARLY_PER_CPU(_type, _name, _initvalue) \
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DEFINE_PER_CPU(_type, _name) = _initvalue
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#define EXPORT_EARLY_PER_CPU_SYMBOL(_name) \
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EXPORT_PER_CPU_SYMBOL(_name)
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#define DECLARE_EARLY_PER_CPU(_type, _name) \
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DECLARE_PER_CPU(_type, _name)
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#define early_per_cpu(_name, _cpu) per_cpu(_name, _cpu)
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#define early_per_cpu_ptr(_name) NULL
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/* no early_per_cpu_map() */
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#endif /* !CONFIG_SMP */
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#endif /* _ASM_X86_PERCPU_H */
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