kernel-ark/arch/sh/kernel/process.c
Nick Piggin 64c7c8f885 [PATCH] sched: resched and cpu_idle rework
Make some changes to the NEED_RESCHED and POLLING_NRFLAG to reduce
confusion, and make their semantics rigid.  Improves efficiency of
resched_task and some cpu_idle routines.

* In resched_task:
- TIF_NEED_RESCHED is only cleared with the task's runqueue lock held,
  and as we hold it during resched_task, then there is no need for an
  atomic test and set there. The only other time this should be set is
  when the task's quantum expires, in the timer interrupt - this is
  protected against because the rq lock is irq-safe.

- If TIF_NEED_RESCHED is set, then we don't need to do anything. It
  won't get unset until the task get's schedule()d off.

- If we are running on the same CPU as the task we resched, then set
  TIF_NEED_RESCHED and no further action is required.

- If we are running on another CPU, and TIF_POLLING_NRFLAG is *not* set
  after TIF_NEED_RESCHED has been set, then we need to send an IPI.

Using these rules, we are able to remove the test and set operation in
resched_task, and make clear the previously vague semantics of
POLLING_NRFLAG.

* In idle routines:
- Enter cpu_idle with preempt disabled. When the need_resched() condition
  becomes true, explicitly call schedule(). This makes things a bit clearer
  (IMO), but haven't updated all architectures yet.

- Many do a test and clear of TIF_NEED_RESCHED for some reason. According
  to the resched_task rules, this isn't needed (and actually breaks the
  assumption that TIF_NEED_RESCHED is only cleared with the runqueue lock
  held). So remove that. Generally one less locked memory op when switching
  to the idle thread.

- Many idle routines clear TIF_POLLING_NRFLAG, and only set it in the inner
  most polling idle loops. The above resched_task semantics allow it to be
  set until before the last time need_resched() is checked before going into
  a halt requiring interrupt wakeup.

  Many idle routines simply never enter such a halt, and so POLLING_NRFLAG
  can be always left set, completely eliminating resched IPIs when rescheduling
  the idle task.

  POLLING_NRFLAG width can be increased, to reduce the chance of resched IPIs.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Con Kolivas <kernel@kolivas.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-11-09 07:56:33 -08:00

522 lines
12 KiB
C

/* $Id: process.c,v 1.28 2004/05/05 16:54:23 lethal Exp $
*
* linux/arch/sh/kernel/process.c
*
* Copyright (C) 1995 Linus Torvalds
*
* SuperH version: Copyright (C) 1999, 2000 Niibe Yutaka & Kaz Kojima
*/
/*
* This file handles the architecture-dependent parts of process handling..
*/
#include <linux/module.h>
#include <linux/unistd.h>
#include <linux/mm.h>
#include <linux/elfcore.h>
#include <linux/slab.h>
#include <linux/a.out.h>
#include <linux/ptrace.h>
#include <linux/platform.h>
#include <linux/kallsyms.h>
#include <asm/io.h>
#include <asm/uaccess.h>
#include <asm/mmu_context.h>
#include <asm/elf.h>
#if defined(CONFIG_SH_HS7751RVOIP)
#include <asm/hs7751rvoip/hs7751rvoip.h>
#elif defined(CONFIG_SH_RTS7751R2D)
#include <asm/rts7751r2d/rts7751r2d.h>
#endif
static int hlt_counter=0;
int ubc_usercnt = 0;
#define HARD_IDLE_TIMEOUT (HZ / 3)
void disable_hlt(void)
{
hlt_counter++;
}
EXPORT_SYMBOL(disable_hlt);
void enable_hlt(void)
{
hlt_counter--;
}
EXPORT_SYMBOL(enable_hlt);
void cpu_idle(void)
{
/* endless idle loop with no priority at all */
while (1) {
if (hlt_counter) {
while (!need_resched())
cpu_relax();
} else {
while (!need_resched())
cpu_sleep();
}
preempt_enable_no_resched();
schedule();
preempt_disable();
}
}
void machine_restart(char * __unused)
{
/* SR.BL=1 and invoke address error to let CPU reset (manual reset) */
asm volatile("ldc %0, sr\n\t"
"mov.l @%1, %0" : : "r" (0x10000000), "r" (0x80000001));
}
void machine_halt(void)
{
#if defined(CONFIG_SH_HS7751RVOIP)
unsigned short value;
value = ctrl_inw(PA_OUTPORTR);
ctrl_outw((value & 0xffdf), PA_OUTPORTR);
#elif defined(CONFIG_SH_RTS7751R2D)
ctrl_outw(0x0001, PA_POWOFF);
#endif
while (1)
cpu_sleep();
}
void machine_power_off(void)
{
#if defined(CONFIG_SH_HS7751RVOIP)
unsigned short value;
value = ctrl_inw(PA_OUTPORTR);
ctrl_outw((value & 0xffdf), PA_OUTPORTR);
#elif defined(CONFIG_SH_RTS7751R2D)
ctrl_outw(0x0001, PA_POWOFF);
#endif
}
void show_regs(struct pt_regs * regs)
{
printk("\n");
printk("Pid : %d, Comm: %20s\n", current->pid, current->comm);
print_symbol("PC is at %s\n", regs->pc);
printk("PC : %08lx SP : %08lx SR : %08lx ",
regs->pc, regs->regs[15], regs->sr);
#ifdef CONFIG_MMU
printk("TEA : %08x ", ctrl_inl(MMU_TEA));
#else
printk(" ");
#endif
printk("%s\n", print_tainted());
printk("R0 : %08lx R1 : %08lx R2 : %08lx R3 : %08lx\n",
regs->regs[0],regs->regs[1],
regs->regs[2],regs->regs[3]);
printk("R4 : %08lx R5 : %08lx R6 : %08lx R7 : %08lx\n",
regs->regs[4],regs->regs[5],
regs->regs[6],regs->regs[7]);
printk("R8 : %08lx R9 : %08lx R10 : %08lx R11 : %08lx\n",
regs->regs[8],regs->regs[9],
regs->regs[10],regs->regs[11]);
printk("R12 : %08lx R13 : %08lx R14 : %08lx\n",
regs->regs[12],regs->regs[13],
regs->regs[14]);
printk("MACH: %08lx MACL: %08lx GBR : %08lx PR : %08lx\n",
regs->mach, regs->macl, regs->gbr, regs->pr);
/*
* If we're in kernel mode, dump the stack too..
*/
if (!user_mode(regs)) {
extern void show_task(unsigned long *sp);
unsigned long sp = regs->regs[15];
show_task((unsigned long *)sp);
}
}
/*
* Create a kernel thread
*/
/*
* This is the mechanism for creating a new kernel thread.
*
*/
extern void kernel_thread_helper(void);
__asm__(".align 5\n"
"kernel_thread_helper:\n\t"
"jsr @r5\n\t"
" nop\n\t"
"mov.l 1f, r1\n\t"
"jsr @r1\n\t"
" mov r0, r4\n\t"
".align 2\n\t"
"1:.long do_exit");
int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
{ /* Don't use this in BL=1(cli). Or else, CPU resets! */
struct pt_regs regs;
memset(&regs, 0, sizeof(regs));
regs.regs[4] = (unsigned long) arg;
regs.regs[5] = (unsigned long) fn;
regs.pc = (unsigned long) kernel_thread_helper;
regs.sr = (1 << 30);
/* Ok, create the new process.. */
return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
}
/*
* Free current thread data structures etc..
*/
void exit_thread(void)
{
if (current->thread.ubc_pc) {
current->thread.ubc_pc = 0;
ubc_usercnt -= 1;
}
}
void flush_thread(void)
{
#if defined(CONFIG_SH_FPU)
struct task_struct *tsk = current;
struct pt_regs *regs = (struct pt_regs *)
((unsigned long)tsk->thread_info
+ THREAD_SIZE - sizeof(struct pt_regs)
- sizeof(unsigned long));
/* Forget lazy FPU state */
clear_fpu(tsk, regs);
clear_used_math();
#endif
}
void release_thread(struct task_struct *dead_task)
{
/* do nothing */
}
/* Fill in the fpu structure for a core dump.. */
int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
{
int fpvalid = 0;
#if defined(CONFIG_SH_FPU)
struct task_struct *tsk = current;
fpvalid = !!tsk_used_math(tsk);
if (fpvalid) {
unlazy_fpu(tsk, regs);
memcpy(fpu, &tsk->thread.fpu.hard, sizeof(*fpu));
}
#endif
return fpvalid;
}
/*
* Capture the user space registers if the task is not running (in user space)
*/
int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
{
struct pt_regs ptregs;
ptregs = *(struct pt_regs *)
((unsigned long)tsk->thread_info + THREAD_SIZE
- sizeof(struct pt_regs)
#ifdef CONFIG_SH_DSP
- sizeof(struct pt_dspregs)
#endif
- sizeof(unsigned long));
elf_core_copy_regs(regs, &ptregs);
return 1;
}
int
dump_task_fpu (struct task_struct *tsk, elf_fpregset_t *fpu)
{
int fpvalid = 0;
#if defined(CONFIG_SH_FPU)
fpvalid = !!tsk_used_math(tsk);
if (fpvalid) {
struct pt_regs *regs = (struct pt_regs *)
((unsigned long)tsk->thread_info
+ THREAD_SIZE - sizeof(struct pt_regs)
- sizeof(unsigned long));
unlazy_fpu(tsk, regs);
memcpy(fpu, &tsk->thread.fpu.hard, sizeof(*fpu));
}
#endif
return fpvalid;
}
asmlinkage void ret_from_fork(void);
int copy_thread(int nr, unsigned long clone_flags, unsigned long usp,
unsigned long unused,
struct task_struct *p, struct pt_regs *regs)
{
struct pt_regs *childregs;
#if defined(CONFIG_SH_FPU)
struct task_struct *tsk = current;
unlazy_fpu(tsk, regs);
p->thread.fpu = tsk->thread.fpu;
copy_to_stopped_child_used_math(p);
#endif
childregs = ((struct pt_regs *)
(THREAD_SIZE + (unsigned long) p->thread_info)
#ifdef CONFIG_SH_DSP
- sizeof(struct pt_dspregs)
#endif
- sizeof(unsigned long)) - 1;
*childregs = *regs;
if (user_mode(regs)) {
childregs->regs[15] = usp;
} else {
childregs->regs[15] = (unsigned long)p->thread_info + THREAD_SIZE;
}
if (clone_flags & CLONE_SETTLS) {
childregs->gbr = childregs->regs[0];
}
childregs->regs[0] = 0; /* Set return value for child */
p->thread.sp = (unsigned long) childregs;
p->thread.pc = (unsigned long) ret_from_fork;
p->thread.ubc_pc = 0;
return 0;
}
/*
* fill in the user structure for a core dump..
*/
void dump_thread(struct pt_regs * regs, struct user * dump)
{
dump->magic = CMAGIC;
dump->start_code = current->mm->start_code;
dump->start_data = current->mm->start_data;
dump->start_stack = regs->regs[15] & ~(PAGE_SIZE - 1);
dump->u_tsize = (current->mm->end_code - dump->start_code) >> PAGE_SHIFT;
dump->u_dsize = (current->mm->brk + (PAGE_SIZE-1) - dump->start_data) >> PAGE_SHIFT;
dump->u_ssize = (current->mm->start_stack - dump->start_stack +
PAGE_SIZE - 1) >> PAGE_SHIFT;
/* Debug registers will come here. */
dump->regs = *regs;
dump->u_fpvalid = dump_fpu(regs, &dump->fpu);
}
/* Tracing by user break controller. */
static void
ubc_set_tracing(int asid, unsigned long pc)
{
ctrl_outl(pc, UBC_BARA);
/* We don't have any ASID settings for the SH-2! */
if (cpu_data->type != CPU_SH7604)
ctrl_outb(asid, UBC_BASRA);
ctrl_outl(0, UBC_BAMRA);
if (cpu_data->type == CPU_SH7729) {
ctrl_outw(BBR_INST | BBR_READ | BBR_CPU, UBC_BBRA);
ctrl_outl(BRCR_PCBA | BRCR_PCTE, UBC_BRCR);
} else {
ctrl_outw(BBR_INST | BBR_READ, UBC_BBRA);
ctrl_outw(BRCR_PCBA, UBC_BRCR);
}
}
/*
* switch_to(x,y) should switch tasks from x to y.
*
*/
struct task_struct *__switch_to(struct task_struct *prev, struct task_struct *next)
{
#if defined(CONFIG_SH_FPU)
struct pt_regs *regs = (struct pt_regs *)
((unsigned long)prev->thread_info
+ THREAD_SIZE - sizeof(struct pt_regs)
- sizeof(unsigned long));
unlazy_fpu(prev, regs);
#endif
#ifdef CONFIG_PREEMPT
{
unsigned long flags;
struct pt_regs *regs;
local_irq_save(flags);
regs = (struct pt_regs *)
((unsigned long)prev->thread_info
+ THREAD_SIZE - sizeof(struct pt_regs)
#ifdef CONFIG_SH_DSP
- sizeof(struct pt_dspregs)
#endif
- sizeof(unsigned long));
if (user_mode(regs) && regs->regs[15] >= 0xc0000000) {
int offset = (int)regs->regs[15];
/* Reset stack pointer: clear critical region mark */
regs->regs[15] = regs->regs[1];
if (regs->pc < regs->regs[0])
/* Go to rewind point */
regs->pc = regs->regs[0] + offset;
}
local_irq_restore(flags);
}
#endif
/*
* Restore the kernel mode register
* k7 (r7_bank1)
*/
asm volatile("ldc %0, r7_bank"
: /* no output */
: "r" (next->thread_info));
#ifdef CONFIG_MMU
/* If no tasks are using the UBC, we're done */
if (ubc_usercnt == 0)
/* If no tasks are using the UBC, we're done */;
else if (next->thread.ubc_pc && next->mm) {
ubc_set_tracing(next->mm->context & MMU_CONTEXT_ASID_MASK,
next->thread.ubc_pc);
} else {
ctrl_outw(0, UBC_BBRA);
ctrl_outw(0, UBC_BBRB);
}
#endif
return prev;
}
asmlinkage int sys_fork(unsigned long r4, unsigned long r5,
unsigned long r6, unsigned long r7,
struct pt_regs regs)
{
#ifdef CONFIG_MMU
return do_fork(SIGCHLD, regs.regs[15], &regs, 0, NULL, NULL);
#else
/* fork almost works, enough to trick you into looking elsewhere :-( */
return -EINVAL;
#endif
}
asmlinkage int sys_clone(unsigned long clone_flags, unsigned long newsp,
unsigned long parent_tidptr,
unsigned long child_tidptr,
struct pt_regs regs)
{
if (!newsp)
newsp = regs.regs[15];
return do_fork(clone_flags, newsp, &regs, 0,
(int __user *)parent_tidptr, (int __user *)child_tidptr);
}
/*
* This is trivial, and on the face of it looks like it
* could equally well be done in user mode.
*
* Not so, for quite unobvious reasons - register pressure.
* In user mode vfork() cannot have a stack frame, and if
* done by calling the "clone()" system call directly, you
* do not have enough call-clobbered registers to hold all
* the information you need.
*/
asmlinkage int sys_vfork(unsigned long r4, unsigned long r5,
unsigned long r6, unsigned long r7,
struct pt_regs regs)
{
return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs.regs[15], &regs,
0, NULL, NULL);
}
/*
* sys_execve() executes a new program.
*/
asmlinkage int sys_execve(char *ufilename, char **uargv,
char **uenvp, unsigned long r7,
struct pt_regs regs)
{
int error;
char *filename;
filename = getname((char __user *)ufilename);
error = PTR_ERR(filename);
if (IS_ERR(filename))
goto out;
error = do_execve(filename,
(char __user * __user *)uargv,
(char __user * __user *)uenvp,
&regs);
if (error == 0) {
task_lock(current);
current->ptrace &= ~PT_DTRACE;
task_unlock(current);
}
putname(filename);
out:
return error;
}
unsigned long get_wchan(struct task_struct *p)
{
unsigned long schedule_frame;
unsigned long pc;
if (!p || p == current || p->state == TASK_RUNNING)
return 0;
/*
* The same comment as on the Alpha applies here, too ...
*/
pc = thread_saved_pc(p);
if (in_sched_functions(pc)) {
schedule_frame = ((unsigned long *)(long)p->thread.sp)[1];
return (unsigned long)((unsigned long *)schedule_frame)[1];
}
return pc;
}
asmlinkage void break_point_trap(unsigned long r4, unsigned long r5,
unsigned long r6, unsigned long r7,
struct pt_regs regs)
{
/* Clear tracing. */
ctrl_outw(0, UBC_BBRA);
ctrl_outw(0, UBC_BBRB);
current->thread.ubc_pc = 0;
ubc_usercnt -= 1;
force_sig(SIGTRAP, current);
}
asmlinkage void break_point_trap_software(unsigned long r4, unsigned long r5,
unsigned long r6, unsigned long r7,
struct pt_regs regs)
{
regs.pc -= 2;
force_sig(SIGTRAP, current);
}