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#include "types.h"
#include "defs.h"
#include "param.h"
#include "mmu.h"
#include "x86.h"
#include "proc.h"
#include "spinlock.h"
struct spinlock proc_table_lock;
struct proc proc[NPROC];
static struct proc *initproc;
int nextpid = 1;
extern void forkret(void);
extern void forkret1(struct trapframe*);
void
pinit(void)
{
initlock(&proc_table_lock, "proc_table");
}
// Look in the process table for an UNUSED proc.
// If found, change state to EMBRYO and return it.
// Otherwise return 0.
static struct proc*
allocproc(void)
{
int i;
struct proc *p;
acquire(&proc_table_lock);
for(i = 0; i < NPROC; i++){
p = &proc[i];
if(p->state == UNUSED){
p->state = EMBRYO;
p->pid = nextpid++;
release(&proc_table_lock);
return p;
}
}
release(&proc_table_lock);
return 0;
}
// Grow current process's memory by n bytes.
// Return old size on success, -1 on failure.
int
growproc(int n)
{
char *newmem, *oldmem;
newmem = kalloc(cp->sz + n);
if(newmem == 0)
return -1;
memmove(newmem, cp->mem, cp->sz);
memset(newmem + cp->sz, 0, n);
oldmem = cp->mem;
cp->mem = newmem;
kfree(oldmem, cp->sz);
cp->sz += n;
setupsegs(cp);
return cp->sz - n;
}
// Set up CPU's segment descriptors and task state for a given process.
// If p==0, set up for "idle" state for when scheduler() is running.
void
setupsegs(struct proc *p)
{
struct cpu *c;
pushcli();
c = &cpus[cpu()];
c->ts.ss0 = SEG_KDATA << 3;
if(p)
c->ts.esp0 = (uint)(p->kstack + KSTACKSIZE);
else
c->ts.esp0 = 0xffffffff;
c->gdt[0] = SEG_NULL;
c->gdt[SEG_KCODE] = SEG(STA_X|STA_R, 0, 0x100000 + 64*1024-1, 0);
c->gdt[SEG_KDATA] = SEG(STA_W, 0, 0xffffffff, 0);
c->gdt[SEG_TSS] = SEG16(STS_T32A, (uint)&c->ts, sizeof(c->ts)-1, 0);
c->gdt[SEG_TSS].s = 0;
if(p){
c->gdt[SEG_UCODE] = SEG(STA_X|STA_R, (uint)p->mem, p->sz-1, DPL_USER);
c->gdt[SEG_UDATA] = SEG(STA_W, (uint)p->mem, p->sz-1, DPL_USER);
} else {
c->gdt[SEG_UCODE] = SEG_NULL;
c->gdt[SEG_UDATA] = SEG_NULL;
}
lgdt(c->gdt, sizeof(c->gdt));
ltr(SEG_TSS << 3);
popcli();
}
// Create a new process copying p as the parent.
// Sets up stack to return as if from system call.
// Caller must set state of returned proc to RUNNABLE.
struct proc*
copyproc(struct proc *p)
{
int i;
struct proc *np;
// Allocate process.
if((np = allocproc()) == 0)
return 0;
// Allocate kernel stack.
if((np->kstack = kalloc(KSTACKSIZE)) == 0){
np->state = UNUSED;
return 0;
}
np->tf = (struct trapframe*)(np->kstack + KSTACKSIZE) - 1;
if(p){ // Copy process state from p.
np->parent = p;
memmove(np->tf, p->tf, sizeof(*np->tf));
np->sz = p->sz;
if((np->mem = kalloc(np->sz)) == 0){
kfree(np->kstack, KSTACKSIZE);
np->kstack = 0;
np->state = UNUSED;
return 0;
}
memmove(np->mem, p->mem, np->sz);
for(i = 0; i < NOFILE; i++)
if(p->ofile[i])
np->ofile[i] = filedup(p->ofile[i]);
np->cwd = idup(p->cwd);
}
// Set up new context to start executing at forkret (see below).
memset(&np->context, 0, sizeof(np->context));
np->context.eip = (uint)forkret;
np->context.esp = (uint)np->tf;
// Clear %eax so that fork system call returns 0 in child.
np->tf->eax = 0;
return np;
}
// Set up first user process.
void
userinit(void)
{
struct proc *p;
extern uchar _binary_initcode_start[], _binary_initcode_size[];
p = copyproc(0);
p->sz = PAGE;
p->mem = kalloc(p->sz);
p->cwd = namei("/");
memset(p->tf, 0, sizeof(*p->tf));
p->tf->cs = (SEG_UCODE << 3) | DPL_USER;
p->tf->ds = (SEG_UDATA << 3) | DPL_USER;
p->tf->es = p->tf->ds;
p->tf->ss = p->tf->ds;
p->tf->eflags = FL_IF;
p->tf->esp = p->sz;
// Make return address readable; needed for some gcc.
p->tf->esp -= 4;
*(uint*)(p->mem + p->tf->esp) = 0xefefefef;
// On entry to user space, start executing at beginning of initcode.S.
p->tf->eip = 0;
memmove(p->mem, _binary_initcode_start, (int)_binary_initcode_size);
safestrcpy(p->name, "initcode", sizeof(p->name));
p->state = RUNNABLE;
initproc = p;
}
// Return currently running process.
struct proc*
curproc(void)
{
struct proc *p;
pushcli();
p = cpus[cpu()].curproc;
popcli();
return p;
}
// Per-CPU process scheduler.
// Each CPU calls scheduler() after setting itself up.
// Scheduler never returns. It loops, doing:
// - choose a process to run
// - swtch to start running that process
// - eventually that process transfers control
// via swtch back to the scheduler.
void
scheduler(void)
{
struct proc *p;
struct cpu *c;
int i;
c = &cpus[cpu()];
for(;;){
// Enable interrupts on this processor.
sti();
// Loop over process table looking for process to run.
acquire(&proc_table_lock);
for(i = 0; i < NPROC; i++){
p = &proc[i];
if(p->state != RUNNABLE)
continue;
// Switch to chosen process. It is the process's job
// to release proc_table_lock and then reacquire it
// before jumping back to us.
c->curproc = p;
setupsegs(p);
p->state = RUNNING;
swtch(&c->context, &p->context);
// Process is done running for now.
// It should have changed its p->state before coming back.
c->curproc = 0;
setupsegs(0);
}
release(&proc_table_lock);
}
}
// Enter scheduler. Must already hold proc_table_lock
// and have changed curproc[cpu()]->state.
void
sched(void)
{
if(read_eflags()&FL_IF)
panic("sched interruptible");
if(cp->state == RUNNING)
panic("sched running");
if(!holding(&proc_table_lock))
panic("sched proc_table_lock");
if(cpus[cpu()].ncli != 1)
panic("sched locks");
swtch(&cp->context, &cpus[cpu()].context);
}
// Give up the CPU for one scheduling round.
void
yield(void)
{
acquire(&proc_table_lock);
cp->state = RUNNABLE;
sched();
release(&proc_table_lock);
}
// A fork child's very first scheduling by scheduler()
// will swtch here. "Return" to user space.
void
forkret(void)
{
// Still holding proc_table_lock from scheduler.
release(&proc_table_lock);
// Jump into assembly, never to return.
forkret1(cp->tf);
}
// Atomically release lock and sleep on chan.
// Reacquires lock when reawakened.
void
sleep(void *chan, struct spinlock *lk)
{
if(cp == 0)
panic("sleep");
if(lk == 0)
panic("sleep without lk");
// Must acquire proc_table_lock in order to
// change p->state and then call sched.
// Once we hold proc_table_lock, we can be
// guaranteed that we won't miss any wakeup
// (wakeup runs with proc_table_lock locked),
// so it's okay to release lk.
if(lk != &proc_table_lock){
acquire(&proc_table_lock);
release(lk);
}
// Go to sleep.
cp->chan = chan;
cp->state = SLEEPING;
sched();
// Tidy up.
cp->chan = 0;
// Reacquire original lock.
if(lk != &proc_table_lock){
release(&proc_table_lock);
acquire(lk);
}
}
// Wake up all processes sleeping on chan.
// Proc_table_lock must be held.
static void
wakeup1(void *chan)
{
struct proc *p;
for(p = proc; p < &proc[NPROC]; p++)
if(p->state == SLEEPING && p->chan == chan)
p->state = RUNNABLE;
}
// Wake up all processes sleeping on chan.
// Proc_table_lock is acquired and released.
void
wakeup(void *chan)
{
acquire(&proc_table_lock);
wakeup1(chan);
release(&proc_table_lock);
}
// Kill the process with the given pid.
// Process won't actually exit until it returns
// to user space (see trap in trap.c).
int
kill(int pid)
{
struct proc *p;
acquire(&proc_table_lock);
for(p = proc; p < &proc[NPROC]; p++){
if(p->pid == pid){
p->killed = 1;
// Wake process from sleep if necessary.
if(p->state == SLEEPING)
p->state = RUNNABLE;
release(&proc_table_lock);
return 0;
}
}
release(&proc_table_lock);
return -1;
}
// Exit the current process. Does not return.
// Exited processes remain in the zombie state
// until their parent calls wait() to find out they exited.
void
exit(void)
{
struct proc *p;
int fd;
if(cp == initproc)
panic("init exiting");
// Close all open files.
for(fd = 0; fd < NOFILE; fd++){
if(cp->ofile[fd]){
fileclose(cp->ofile[fd]);
cp->ofile[fd] = 0;
}
}
iput(cp->cwd);
cp->cwd = 0;
acquire(&proc_table_lock);
// Parent might be sleeping in wait().
wakeup1(cp->parent);
// Pass abandoned children to init.
for(p = proc; p < &proc[NPROC]; p++){
if(p->parent == cp){
p->parent = initproc;
if(p->state == ZOMBIE)
wakeup1(initproc);
}
}
// Jump into the scheduler, never to return.
cp->killed = 0;
cp->state = ZOMBIE;
sched();
panic("zombie exit");
}
// Wait for a child process to exit and return its pid.
// Return -1 if this process has no children.
int
wait(void)
{
struct proc *p;
int i, havekids, pid;
acquire(&proc_table_lock);
for(;;){
// Scan through table looking for zombie children.
havekids = 0;
for(i = 0; i < NPROC; i++){
p = &proc[i];
if(p->state == UNUSED)
continue;
if(p->parent == cp){
if(p->state == ZOMBIE){
// Found one.
kfree(p->mem, p->sz);
kfree(p->kstack, KSTACKSIZE);
pid = p->pid;
p->state = UNUSED;
p->pid = 0;
p->parent = 0;
p->name[0] = 0;
release(&proc_table_lock);
return pid;
}
havekids = 1;
}
}
// No point waiting if we don't have any children.
if(!havekids || cp->killed){
release(&proc_table_lock);
return -1;
}
// Wait for children to exit. (See wakeup1 call in proc_exit.)
sleep(cp, &proc_table_lock);
}
}
// Print a process listing to console. For debugging.
// Runs when user types ^P on console.
// No lock to avoid wedging a stuck machine further.
void
procdump(void)
{
static char *states[] = {
[UNUSED] "unused",
[EMBRYO] "embryo",
[SLEEPING] "sleep ",
[RUNNABLE] "runble",
[RUNNING] "run ",
[ZOMBIE] "zombie"
};
int i, j;
struct proc *p;
char *state;
uint pc[10];
for(i = 0; i < NPROC; i++){
p = &proc[i];
if(p->state == UNUSED)
continue;
if(p->state >= 0 && p->state < NELEM(states) && states[p->state])
state = states[p->state];
else
state = "???";
cprintf("%d %s %s", p->pid, state, p->name);
if(p->state == SLEEPING){
getcallerpcs((uint*)p->context.ebp+2, pc);
for(j=0; j<10 && pc[j] != 0; j++)
cprintf(" %p", pc[j]);
}
cprintf("\n");
}
}
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