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Commit ec7fcaab authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge Committed by Andi Kleen
Browse files

[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: default avatarJeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: default avatarAndi 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: default avatarAndrew Morton <akpm@osdl.org>
parent b2938f88

arch/i386/kernel/asm-offsets.c

+2 −0
Original line number Diff line number Diff line
@@ -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);

}

arch/i386/kernel/cpu/common.c

+2 −0
Original line number Diff line number Diff line
@@ -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;

}

arch/i386/kernel/process.c

+1 −0
Original line number Diff line number Diff line
@@ -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.

include/asm-i386/current.h

+4 −3
Original line number Diff line number Diff line 
#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)

{

	return current_thread_info()->task;

	return read_pda(pcurrent);

}

 

#define current get_current()

include/asm-i386/pda.h

+2 −0
Original line number Diff line number Diff line
@@ -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[];