Plik zawiera funkcję związane z zarządzaniem procesami dla architektury Intela.
Skomentowano tutaj funkcje realizujące "nudzenie" się procesora -
pętla wykonywana przez proces o identyfikatorze 0 (proces idle):
sys_idle() oraz hard_idle().
(gc)
/*
* linux/arch/i386/kernel/process.c
*
* Copyright (C) 1995 Linus Torvalds
*/
/*
* This file handles the architecture-dependent parts of process handling..
*/
#define __KERNEL_SYSCALLS__
#include <stdarg.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/ptrace.h>
#include <linux/malloc.h>
#include <linux/ldt.h>
#include <linux/user.h>
#include <linux/a.out.h>
#include <linux/interrupt.h>
#include <linux/config.h>
#include <linux/unistd.h>
#include <linux/delay.h>
#include <asm/segment.h>
#include <asm/pgtable.h>
#include <asm/system.h>
#include <asm/io.h>
#include <linux/smp.h>
asmlinkage void ret_from_sys_call(void) __asm__("ret_from_sys_call");
#ifdef CONFIG_APM
extern int apm_do_idle(void);
extern void apm_do_busy(void);
#endif
static int hlt_counter=0;
#define HARD_IDLE_TIMEOUT (HZ / 3)
void disable_hlt(void)
{
hlt_counter++;
}
void enable_hlt(void)
{
hlt_counter--;
}
Funkcja "sprzętowego" idle. Jeśli jądro zostało skompilowane ze opcją CONFIG_APM, zostanie wywołana funckja BIOS'u. W zależności od typu BIOS'u i jego konfiguracji może dojść do wyłączenia niektórych urządzeń takich jak monitor, twarde dyski, wentylator procesora.
#ifndef __SMP__
static void hard_idle(void)
{
while (!need_resched) {
if (hlt_works_ok && !hlt_counter) {
#ifdef CONFIG_APM
/* If the APM BIOS is not enabled, or there
is an error calling the idle routine, we
should hlt if possible. We need to check
need_resched again because an interrupt
may have occurred in apm_do_idle(). */
start_bh_atomic();
if (!apm_do_idle() && !need_resched)
__asm__("hlt");
end_bh_atomic();
#else
__asm__("hlt");
#endif
}
if (need_resched)
break;
schedule();
}
Włącz urządzenia, które mogły zostać wyłączone przez BIOS.
#ifdef CONFIG_APM apm_do_busy(); #endif }
(gc)
Funkcja realizująca idle-loop procesora - wykonywana przez proces wymiany (o pid równym 0), wtedy gdy procesor się nudzi, czyli gdy kolejka procesów gotowych jest pusta.
/*
* The idle loop on a uniprocessor i386..
*/
asmlinkage int sys_idle(void)
{
unsigned long start_idle = 0;
Tylko proces wymiany może wykonywać sys_idle().
if (current->pid != 0) return -EPERM; /* endless idle loop with no priority at all */
Ustaw wartość dynamicznego priorytetu mniejszą niż 0, ale większą niż -1000. (Patrz funkcja schedule() w kernel/sched.c.
current->counter = -100;
for (;;)
{
/*
* We are locked at this point. So we can safely call
* the APM bios knowing only one CPU at a time will do
* so.
*/
Zapamiętaj "godzinę", w którym procesor zaczął się "nudzić".
if (!start_idle)
start_idle = jiffies;
if (jiffies - start_idle > HARD_IDLE_TIMEOUT)
{
Jeśli pętla idle wykonuje się dłużej niż 330ms (dla Intela HARD_IDLE_TIMEOUT = 33; zegar systemowy tyka co 10ms) wykonaj sprzętowy idle - hard_idle().
hard_idle();
}
else
{
Wpp, jeśli procesor zawiera poprawnie działającą instukcję hlt, wstrzymaj jego działanie. Stare wersje procesorów i386 oraz niektóre i486DX4 mają z nią problemy - w takim przypadku trzeba czekać aktywnie.
if (hlt_works_ok && !hlt_counter && !need_resched)
__asm__("hlt");
}
W wyniku przerwania flaga need_resched mogła zostać ustawiona. Jeśli tak, oddaj procesor.
if (need_resched) start_idle = 0; schedule(); } } #else
(gc)
/*
* In the SMP world we hlt outside of kernel syscall rather than within
* so as to get the right locking semantics.
*/
asmlinkage int sys_idle(void)
{
if(current->pid != 0)
return -EPERM;
#ifdef __SMP_PROF__
smp_spins_sys_idle[smp_processor_id()]+=
smp_spins_syscall_cur[smp_processor_id()];
#endif
current->counter= -100;
schedule();
return 0;
}
(gc)
/*
* This is being executed in task 0 'user space'.
*/
int cpu_idle(void *unused)
{
while(1)
{
Jeśli to możliwe zatrzymaj procesor.
if(cpu_data[smp_processor_id()].hlt_works_ok && !hlt_counter && !need_resched)
__asm("hlt");
Wznowiono działanie w wyniku przerwania.
if(0==(0x7fffffff & smp_process_available))
continue;
Pojawiły się gotowe, nie wykonywane procesy. Poczekaj na podniesienie semafora - stanowi go najstarszy bit zmiennej smp_process_available
while(0x80000000 & smp_process_available);
cli();
Opuść semafor. Makro set_bit to właściwie instrukcja typu "test&set" - wykonuje się atomowo.
while(set_bit(31,&smp_process_available))
while(test_bit(31,&smp_process_available))
{
W czasie wykonywania pętli może nadejść żądanie wyczyszczenia pamięci podręcznej. Ponieważ przerwania są wyłączone należy sprawdzić to explicite.
/*
* Oops.. This is kind of important in some cases...
*/
if(clear_bit(smp_processor_id(), &smp_invalidate_needed))
local_flush_tlb();
}
if (0==(0x7fffffff & smp_process_available)){
clear_bit(31,&smp_process_available);
sti();
continue;
}
smp_process_available--;
clear_bit(31,&smp_process_available);
sti();
Wywołaj funkcję sys_idle(), zdefiniowaną powyżej. Uwaga! Wywołanie z "sys_" spowoduje, że przejdziemy do trybu jądra! W tej chwili procesor jest w trybie użytkownika.
idle(); } } #endif
(gc)
/*
* This routine reboots the machine by asking the keyboard
* controller to pulse the reset-line low. We try that for a while,
* and if it doesn't work, we do some other stupid things.
*/
static long no_idt[2] = {0, 0};
static int reboot_mode = 0;
static int reboot_thru_bios = 0;
void reboot_setup(char *str, int *ints)
{
while(1) {
switch (*str) {
case 'w': /* "warm" reboot (no memory testing etc) */
reboot_mode = 0x1234;
break;
case 'c': /* "cold" reboot (with memory testing etc) */
reboot_mode = 0x0;
break;
case 'b': /* "bios" reboot by jumping through the BIOS */
reboot_thru_bios = 1;
break;
case 'h': /* "hard" reboot by toggling RESET and/or crashing the CPU */
reboot_thru_bios = 0;
break;
}
if((str = strchr(str,',')) != NULL)
str++;
else
break;
}
}
/* The following code and data reboots the machine by switching to real
mode and jumping to the BIOS reset entry point, as if the CPU has
really been reset. The previous version asked the keyboard
controller to pulse the CPU reset line, which is more thorough, but
doesn't work with at least one type of 486 motherboard. It is easy
to stop this code working; hence the copious comments. */
unsigned long long
real_mode_gdt_entries [3] =
{
0x0000000000000000ULL, /* Null descriptor */
0x00009a000000ffffULL, /* 16-bit real-mode 64k code at 0x00000000 */
0x000092000100ffffULL /* 16-bit real-mode 64k data at 0x00000100 */
};
struct
{
unsigned short size __attribute__ ((packed));
unsigned long long * base __attribute__ ((packed));
}
real_mode_gdt = { sizeof (real_mode_gdt_entries) - 1, real_mode_gdt_entries },
real_mode_idt = { 0x3ff, 0 };
/* This is 16-bit protected mode code to disable paging and the cache,
switch to real mode and jump to the BIOS reset code.
The instruction that switches to real mode by writing to CR0 must be
followed immediately by a far jump instruction, which set CS to a
valid value for real mode, and flushes the prefetch queue to avoid
running instructions that have already been decoded in protected
mode.
Clears all the flags except ET, especially PG (paging), PE
(protected-mode enable) and TS (task switch for coprocessor state
save). Flushes the TLB after paging has been disabled. Sets CD and
NW, to disable the cache on a 486, and invalidates the cache. This
is more like the state of a 486 after reset. I don't know if
something else should be done for other chips.
More could be done here to set up the registers as if a CPU reset had
occurred; hopefully real BIOSes don't assume much. */
unsigned char real_mode_switch [] =
{
0x66, 0x0f, 0x20, 0xc0, /* movl %cr0,%eax */
0x66, 0x83, 0xe0, 0x11, /* andl $0x00000011,%eax */
0x66, 0x0d, 0x00, 0x00, 0x00, 0x60, /* orl $0x60000000,%eax */
0x66, 0x0f, 0x22, 0xc0, /* movl %eax,%cr0 */
0x66, 0x0f, 0x22, 0xd8, /* movl %eax,%cr3 */
0x66, 0x0f, 0x20, 0xc3, /* movl %cr0,%ebx */
0x66, 0x81, 0xe3, 0x00, 0x00, 0x00, 0x60, /* andl $0x60000000,%ebx */
0x74, 0x02, /* jz f */
0x0f, 0x08, /* invd */
0x24, 0x10, /* f: andb $0x10,al */
0x66, 0x0f, 0x22, 0xc0, /* movl %eax,%cr0 */
0xea, 0x00, 0x00, 0xff, 0xff /* ljmp $0xffff,$0x0000 */
};
static inline void kb_wait(void)
{
int i;
for (i=0; i<0x10000; i++)
if ((inb_p(0x64) & 0x02) == 0)
break;
}
void hard_reset_now (void)
{
if(!reboot_thru_bios) {
sti();
/* rebooting needs to touch the page at absolute addr 0 */
pg0[0] = 7;
*((unsigned short *)0x472) = reboot_mode;
for (;;) {
int i;
for (i=0; i<100; i++) {
int j;
kb_wait();
for(j = 0; j < 100000 ; j++)
/* nothing */;
outb(0xfe,0x64); /* pulse reset low */
udelay(10);
}
__asm__ __volatile__("\tlidt %0": "=m" (no_idt));
}
}
cli ();
/* Write zero to CMOS register number 0x0f, which the BIOS POST
routine will recognize as telling it to do a proper reboot. (Well
that's what this book in front of me says -- it may only apply to
the Phoenix BIOS though, it's not clear). At the same time,
disable NMIs by setting the top bit in the CMOS address register,
as we're about to do peculiar things to the CPU. I'm not sure if
`outb_p' is needed instead of just `outb'. Use it to be on the
safe side. */
outb_p (0x8f, 0x70);
outb_p (0x00, 0x71);
/* Remap the kernel at virtual address zero, as well as offset zero
from the kernel segment. This assumes the kernel segment starts at
virtual address 0xc0000000. */
memcpy (swapper_pg_dir, swapper_pg_dir + 768,
sizeof (swapper_pg_dir [0]) * 256);
/* Make sure the first page is mapped to the start of physical memory.
It is normally not mapped, to trap kernel NULL pointer dereferences. */
pg0 [0] = 7;
/* Use `swapper_pg_dir' as our page directory. Don't bother with
`SET_PAGE_DIR' because interrupts are disabled and we're rebooting.
This instruction flushes the TLB. */
__asm__ __volatile__ ("movl %0,%%cr3" : : "a" (swapper_pg_dir) : "memory");
/* Write 0x1234 to absolute memory location 0x472. The BIOS reads
this on booting to tell it to "Bypass memory test (also warm
boot)". This seems like a fairly standard thing that gets set by
REBOOT.COM programs, and the previous reset routine did this
too. */
*((unsigned short *)0x472) = reboot_mode;
/* For the switch to real mode, copy some code to low memory. It has
to be in the first 64k because it is running in 16-bit mode, and it
has to have the same physical and virtual address, because it turns
off paging. Copy it near the end of the first page, out of the way
of BIOS variables. */
memcpy ((void *) (0x1000 - sizeof (real_mode_switch)),
real_mode_switch, sizeof (real_mode_switch));
/* Set up the IDT for real mode. */
__asm__ __volatile__ ("lidt %0" : : "m" (real_mode_idt));
/* Set up a GDT from which we can load segment descriptors for real
mode. The GDT is not used in real mode; it is just needed here to
prepare the descriptors. */
__asm__ __volatile__ ("lgdt %0" : : "m" (real_mode_gdt));
/* Load the data segment registers, and thus the descriptors ready for
real mode. The base address of each segment is 0x100, 16 times the
selector value being loaded here. This is so that the segment
registers don't have to be reloaded after switching to real mode:
the values are consistent for real mode operation already. */
__asm__ __volatile__ ("movw $0x0010,%%ax\n"
"\tmovw %%ax,%%ds\n"
"\tmovw %%ax,%%es\n"
"\tmovw %%ax,%%fs\n"
"\tmovw %%ax,%%gs\n"
"\tmovw %%ax,%%ss" : : : "eax");
/* Jump to the 16-bit code that we copied earlier. It disables paging
and the cache, switches to real mode, and jumps to the BIOS reset
entry point. */
__asm__ __volatile__ ("ljmp $0x0008,%0"
:
: "i" ((void *) (0x1000 - sizeof (real_mode_switch))));
}
void show_regs(struct pt_regs * regs)
{
printk("\n");
printk("EIP: %04x:[<%08lx>]",0xffff & regs->cs,regs->eip);
if (regs->cs & 3)
printk(" ESP: %04x:%08lx",0xffff & regs->ss,regs->esp);
printk(" EFLAGS: %08lx\n",regs->eflags);
printk("EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",
regs->eax,regs->ebx,regs->ecx,regs->edx);
printk("ESI: %08lx EDI: %08lx EBP: %08lx",
regs->esi, regs->edi, regs->ebp);
printk(" DS: %04x ES: %04x FS: %04x GS: %04x\n",
0xffff & regs->ds,0xffff & regs->es,
0xffff & regs->fs,0xffff & regs->gs);
}
/*
* Free current thread data structures etc..
*/
void exit_thread(void)
{
/* forget lazy i387 state */
if (last_task_used_math == current)
last_task_used_math = NULL;
/* forget local segments */
__asm__ __volatile__("mov %w0,%%fs ; mov %w0,%%gs ; lldt %w0"
: /* no outputs */
: "r" (0));
current->tss.ldt = 0;
if (current->ldt) {
void * ldt = current->ldt;
current->ldt = NULL;
vfree(ldt);
}
}
void flush_thread(void)
{
int i;
if (current->ldt) {
free_page((unsigned long) current->ldt);
current->ldt = NULL;
for (i=1 ; i<NR_TASKS ; i++) {
if (task[i] == current) {
set_ldt_desc(gdt+(i<<1)+
FIRST_LDT_ENTRY,&default_ldt, 1);
load_ldt(i);
}
}
}
for (i=0 ; i<8 ; i++)
current->debugreg[i] = 0;
/*
* Forget coprocessor state..
*/
#ifdef __SMP__
if (current->flags & PF_USEDFPU) {
stts();
}
#else
if (last_task_used_math == current) {
last_task_used_math = NULL;
stts();
}
#endif
current->used_math = 0;
current->flags &= ~PF_USEDFPU;
}
void release_thread(struct task_struct *dead_task)
{
}
void copy_thread(int nr, unsigned long clone_flags, unsigned long esp,
struct task_struct * p, struct pt_regs * regs)
{
int i;
struct pt_regs * childregs;
p->tss.es = KERNEL_DS;
p->tss.cs = KERNEL_CS;
p->tss.ss = KERNEL_DS;
p->tss.ds = KERNEL_DS;
p->tss.fs = USER_DS;
p->tss.gs = KERNEL_DS;
p->tss.ss0 = KERNEL_DS;
p->tss.esp0 = p->kernel_stack_page + PAGE_SIZE;
p->tss.tr = _TSS(nr);
childregs = ((struct pt_regs *) (p->kernel_stack_page + PAGE_SIZE)) - 1;
p->tss.esp = (unsigned long) childregs;
p->tss.eip = (unsigned long) ret_from_sys_call;
*childregs = *regs;
childregs->eax = 0;
childregs->esp = esp;
p->tss.back_link = 0;
p->tss.eflags = regs->eflags & 0xffffcfff; /* iopl is always 0 for a new process */
p->tss.ldt = _LDT(nr);
if (p->ldt) {
p->ldt = (struct desc_struct*) vmalloc(LDT_ENTRIES*LDT_ENTRY_SIZE);
if (p->ldt != NULL)
memcpy(p->ldt, current->ldt, LDT_ENTRIES*LDT_ENTRY_SIZE);
}
set_tss_desc(gdt+(nr<<1)+FIRST_TSS_ENTRY,&(p->tss));
if (p->ldt)
set_ldt_desc(gdt+(nr<<1)+FIRST_LDT_ENTRY,p->ldt, 512);
else
set_ldt_desc(gdt+(nr<<1)+FIRST_LDT_ENTRY,&default_ldt, 1);
p->tss.bitmap = offsetof(struct thread_struct,io_bitmap);
for (i = 0; i < IO_BITMAP_SIZE+1 ; i++) /* IO bitmap is actually SIZE+1 */
p->tss.io_bitmap[i] = ~0;
if (last_task_used_math == current)
__asm__("clts ; fnsave %0 ; frstor %0":"=m" (p->tss.i387));
}
/*
* fill in the fpu structure for a core dump..
*/
int dump_fpu (struct pt_regs * regs, struct user_i387_struct* fpu)
{
int fpvalid;
if (hard_math) {
if ((fpvalid = current->used_math) != 0) {
#ifdef __SMP__
if (current->flags & PF_USEDFPU)
#else
if (last_task_used_math == current)
#endif
__asm__("clts ; fnsave %0": :"m" (*fpu));
else
memcpy(fpu,¤t->tss.i387.hard,sizeof(*fpu));
}
} else {
/* We dump the emulator state here.
We convert it into standard 387 format first.. */
#ifdef CONFIG_MATH_EMULATION
int i;
unsigned long top;
char (*hardreg)[10];
struct i387_soft_struct *soft_fpu = ¤t->tss.i387.soft;
struct fpu_reg* softreg;
long int control_word = soft_fpu->cwd;
fpu->cwd = soft_fpu->cwd;
fpu->swd = soft_fpu->swd;
fpu->twd = soft_fpu->twd;
fpu->fip = soft_fpu->fip;
fpu->fcs = soft_fpu->fcs;
fpu->foo = soft_fpu->foo;
fpu->fos = soft_fpu->fos;
hardreg = (char (*)[10]) &fpu->st_space[0];
top = (unsigned long) soft_fpu->top % 8;
softreg = &soft_fpu->regs[top];
for (i = top ; i < 8; i ++) {
softreg_to_hardreg(softreg, *hardreg, control_word);
hardreg++;
softreg++;
}
softreg = &soft_fpu->regs[0];
for (i = 0; i < top; i++) {
softreg_to_hardreg(softreg, *hardreg, control_word);
hardreg++;
softreg++;
}
fpvalid = 1;
#else /* defined(CONFIG_MATH_EMULATION) */
fpvalid = 0;
#endif /* !defined(CONFIG_MATH_EMULATION) */
}
return fpvalid;
}
/*
* fill in the user structure for a core dump..
*/
void dump_thread(struct pt_regs * regs, struct user * dump)
{
int i;
/* changed the size calculations - should hopefully work better. lbt */
dump->magic = CMAGIC;
dump->start_code = 0;
dump->start_stack = regs->esp & ~(PAGE_SIZE - 1);
dump->u_tsize = ((unsigned long) current->mm->end_code) >> PAGE_SHIFT;
dump->u_dsize = ((unsigned long) (current->mm->brk + (PAGE_SIZE-1))) >> PAGE_SHIFT;
dump->u_dsize -= dump->u_tsize;
dump->u_ssize = 0;
for (i = 0; i < 8; i++)
dump->u_debugreg[i] = current->debugreg[i];
if (dump->start_stack < TASK_SIZE)
dump->u_ssize = ((unsigned long) (TASK_SIZE - dump->start_stack)) >> PAGE_SHIFT;
dump->regs = *regs;
dump->u_fpvalid = dump_fpu (regs, &dump->i387);
}
asmlinkage int sys_fork(struct pt_regs regs)
{
return do_fork(SIGCHLD, regs.esp, ®s);
}
asmlinkage int sys_clone(struct pt_regs regs)
{
unsigned long clone_flags;
unsigned long newsp;
clone_flags = regs.ebx;
newsp = regs.ecx;
if (!newsp)
newsp = regs.esp;
return do_fork(clone_flags, newsp, ®s);
}
/*
* sys_execve() executes a new program.
*/
asmlinkage int sys_execve(struct pt_regs regs)
{
int error;
char * filename;
error = getname((char *) regs.ebx, &filename);
if (error)
return error;
error = do_execve(filename, (char **) regs.ecx, (char **) regs.edx, ®s);
putname(filename);
return error;
}