kernel-fxtec-pro1x/arch/x86/include/asm/current.h
Ingo Molnar 6dbde35308 percpu: add optimized generic percpu accessors
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>
2009-01-16 14:20:31 +01:00

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C

#ifndef _ASM_X86_CURRENT_H
#define _ASM_X86_CURRENT_H
#ifdef CONFIG_X86_32
#include <linux/compiler.h>
#include <asm/percpu.h>
struct task_struct;
DECLARE_PER_CPU(struct task_struct *, current_task);
static __always_inline struct task_struct *get_current(void)
{
return percpu_read(current_task);
}
#else /* X86_32 */
#ifndef __ASSEMBLY__
#include <asm/pda.h>
struct task_struct;
static __always_inline struct task_struct *get_current(void)
{
return read_pda(pcurrent);
}
#else /* __ASSEMBLY__ */
#include <asm/asm-offsets.h>
#define GET_CURRENT(reg) movq %gs:(pda_pcurrent),reg
#endif /* __ASSEMBLY__ */
#endif /* X86_32 */
#define current get_current()
#endif /* _ASM_X86_CURRENT_H */