[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>
diff --git a/arch/i386/kernel/asm-offsets.c b/arch/i386/kernel/asm-offsets.c
index 85f1b03..0666eb0e 100644
--- a/arch/i386/kernel/asm-offsets.c
+++ b/arch/i386/kernel/asm-offsets.c
@@ -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 @@
BLANK();
OFFSET(PDA_cpu, i386_pda, cpu_number);
+ OFFSET(PDA_pcurrent, i386_pda, pcurrent);
}
diff --git a/arch/i386/kernel/cpu/common.c b/arch/i386/kernel/cpu/common.c
index e476202..6958ae5 100644
--- a/arch/i386/kernel/cpu/common.c
+++ b/arch/i386/kernel/cpu/common.c
@@ -651,6 +651,7 @@
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 @@
memset(pda, 0, sizeof(*pda));
pda->_pda = pda;
pda->cpu_number = cpu;
+ pda->pcurrent = idle;
return 1;
}
diff --git a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c
index dc42725..8749b10 100644
--- a/arch/i386/kernel/process.c
+++ b/arch/i386/kernel/process.c
@@ -684,6 +684,7 @@
if (unlikely(prev->fs | next->fs))
loadsegment(fs, next->fs);
+ write_pda(pcurrent, next_p);
/*
* Restore IOPL if needed.
diff --git a/include/asm-i386/current.h b/include/asm-i386/current.h
index 3cbbecd..5252ee0 100644
--- a/include/asm-i386/current.h
+++ b/include/asm-i386/current.h
@@ -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()
diff --git a/include/asm-i386/pda.h b/include/asm-i386/pda.h
index f90fde2..08a35c4 100644
--- a/include/asm-i386/pda.h
+++ b/include/asm-i386/pda.h
@@ -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[];