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[PATCH] i386: Implement "current" with the PDA 

Use the pcurrent field in the PDA to implement the "current" macro.  This ends
up compiling down to a single instruction to get the current task.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Chuck Ebbert <76306.1226@compuserve.com>
Cc: Zachary Amsden <zach@vmware.com>
Cc: Jan Beulich <jbeulich@novell.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
This commit is contained in:
Jeremy Fitzhardinge 2006-12-07 02:14:03 +01:00 committed by Andi Kleen
parent b2938f8808
commit ec7fcaabbf
5 changed files with 11 additions and 3 deletions
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2
arch/i386/kernel/asm-offsets.c
View File

@ -15,6 +15,7 @@
#include <asm/processor.h>
#include <asm/thread_info.h>
#include <asm/elf.h>
#include <asm/pda.h>
#define DEFINE(sym, val) \
asm volatile("\n->" #sym " %0 " #val : : "i" (val))
@ -99,4 +100,5 @@ void foo(void)
BLANK();
OFFSET(PDA_cpu, i386_pda, cpu_number);
OFFSET(PDA_pcurrent, i386_pda, pcurrent);
}

2
arch/i386/kernel/cpu/common.c
View File

@ -651,6 +651,7 @@ __cpuinit int alloc_gdt(int cpu)
struct i386_pda boot_pda = {
._pda = &boot_pda,
.cpu_number = 0,
.pcurrent = &init_task,
};
static inline void set_kernel_gs(void)
@ -696,6 +697,7 @@ __cpuinit int init_gdt(int cpu, struct task_struct *idle)
memset(pda, 0, sizeof(*pda));
pda->_pda = pda;
pda->cpu_number = cpu;
pda->pcurrent = idle;
return 1;
}

1
arch/i386/kernel/process.c
View File

@ -684,6 +684,7 @@ struct task_struct fastcall * __switch_to(struct task_struct *prev_p, struct tas
if (unlikely(prev->fs | next->fs))
loadsegment(fs, next->fs);
write_pda(pcurrent, next_p);
/*
* Restore IOPL if needed.

7
include/asm-i386/current.h
View File

@ -1,13 +1,14 @@
#ifndef _I386_CURRENT_H
#define _I386_CURRENT_H
#include <linux/thread_info.h>
#include <asm/pda.h>
#include <linux/compiler.h>
struct task_struct;
static __always_inline struct task_struct * get_current(void)
static __always_inline struct task_struct *get_current(void)
{
return current_thread_info()->task;
return read_pda(pcurrent);
}
#define current get_current()

2
include/asm-i386/pda.h
View File

@ -7,12 +7,14 @@
#define _I386_PDA_H
#include <linux/stddef.h>
#include <linux/types.h>
struct i386_pda
{
struct i386_pda *_pda; /* pointer to self */
int cpu_number;
struct task_struct *pcurrent; /* current process */
};
extern struct i386_pda *_cpu_pda[];