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提交 46bbd72f 创建 作者: rtm's avatar rtm
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no more recursive locks

wakeup1() assumes you hold proc_table_lock sleep(chan, lock) provides atomic sleep-and-release to wait for condition ugly code in swtch/scheduler to implement new sleep fix lots of bugs in pipes, wait, and exit fix bugs if timer interrupt goes off in schedule() console locks per line, not per byte
上级 d9872ffa
隐藏空白字符变更
内嵌 并排
正在显示 包含 229 行增加 和 102 行删除
Notes
浏览文件 @ 46bbd72f
......@@ -126,3 +126,26 @@ nasty hack to allow locks before first process,
race between release and sleep in sys_wait()
race between sys_exit waking up parent and setting state=ZOMBIE
race in pipe code when full/empty
lock order
per-pipe lock
proc_table_lock fd_table_lock kalloc_lock
console_lock
condition variable + mutex that protects it
proc * (for wait()), proc_table_lock
pipe structure, pipe lock
systematic way to test sleep races?
print something at the start of sleep?
do you have to be holding the mutex in order to call wakeup()?
should lock around printf, not putc
device interrupts don't clear FL_IF
so a recursive timer interrupt is possible
the sleep/swtch/schedule code that holds over a lock is ugly
console.c
浏览文件 @ 46bbd72f
......@@ -4,7 +4,8 @@
#include "spinlock.h"
struct spinlock console_lock;
int use_printf_lock = 0;
int paniced = 0;
int use_console_lock = 0;
/*
* copy console output to parallel port, which you can tell
......@@ -23,15 +24,18 @@ lpt_putc(int c)
outb(0x378+2, 0x08);
}
void
cons_putc(int c)
static void
real_cons_putc(int c)
{
int crtport = 0x3d4; // io port of CGA
unsigned short *crt = (unsigned short *) 0xB8000; // base of CGA memory
int ind;
if(use_printf_lock)
acquire(&console_lock);
if(paniced){
cli();
while(1)
;
}
lpt_putc(c);
......@@ -63,8 +67,15 @@ cons_putc(int c)
outb(crtport + 1, ind >> 8);
outb(crtport, 15);
outb(crtport + 1, ind);
}
if(use_printf_lock)
void
cons_putc(int c)
{
if(use_console_lock)
acquire(&console_lock);
real_cons_putc(c);
if(use_console_lock)
release(&console_lock);
}
......@@ -91,7 +102,7 @@ printint(int xx, int base, int sgn)
while(i > 0){
i -= 1;
cons_putc(buf[i]);
real_cons_putc(buf[i]);
}
}
......@@ -104,13 +115,16 @@ cprintf(char *fmt, ...)
int i, state = 0, c;
unsigned int *ap = (unsigned int *) &fmt + 1;
if(use_console_lock)
acquire(&console_lock);
for(i = 0; fmt[i]; i++){
c = fmt[i] & 0xff;
if(state == 0){
if(c == '%'){
state = '%';
} else {
cons_putc(c);
real_cons_putc(c);
}
} else if(state == '%'){
if(c == 'd'){
......@@ -120,20 +134,25 @@ cprintf(char *fmt, ...)
printint(*ap, 16, 0);
ap++;
} else if(c == '%'){
cons_putc(c);
real_cons_putc(c);
}
state = 0;
}
}
if(use_console_lock)
release(&console_lock);
}
void
panic(char *s)
{
use_printf_lock = 0;
__asm __volatile("cli");
use_console_lock = 0;
cprintf("panic: ");
cprintf(s, 0);
cprintf("\n", 0);
paniced = 1; // freeze other CPU
while(1)
;
}
defs.h
浏览文件 @ 46bbd72f
......@@ -14,7 +14,8 @@ struct jmpbuf;
void setupsegs(struct proc *);
struct proc * newproc(void);
void swtch(int);
void sleep(void *);
struct spinlock;
void sleep(void *, struct spinlock *);
void wakeup(void *);
void scheduler(void);
void proc_exit(void);
......@@ -65,6 +66,8 @@ int cpu(void);
struct spinlock;
void acquire(struct spinlock * lock);
void release(struct spinlock * lock);
void acquire1(struct spinlock * lock, struct proc *);
void release1(struct spinlock * lock, struct proc *);
// main.c
void load_icode(struct proc *p, uint8_t *binary, unsigned size);
......
ide.c
浏览文件 @ 46bbd72f
......@@ -112,7 +112,7 @@ ide_start_read(uint32_t secno, void *dst, unsigned nsecs)
panic("ide_start_read: nsecs too large");
while ((head + 1) % NREQUEST == tail)
sleep (&disk_channel);
sleep (&disk_channel, 0);
r = &request[head];
r->secno = secno;
......
main.c
浏览文件 @ 46bbd72f
......@@ -16,7 +16,7 @@ extern char _binary_user1_start[], _binary_user1_size[];
extern char _binary_usertests_start[], _binary_usertests_size[];
extern char _binary_userfs_start[], _binary_userfs_size[];
extern use_printf_lock;
extern int use_console_lock;
int
main()
......@@ -40,7 +40,7 @@ main()
mp_init(); // collect info about this machine
use_printf_lock = 1;
use_console_lock = 1;
cpus[cpu()].clis = 1; // cpu starts as if we had called cli()
......
pipe.c
浏览文件 @ 46bbd72f
......@@ -81,16 +81,17 @@ pipe_write(struct pipe *p, char *addr, int n)
for(i = 0; i < n; i++){
while(((p->writep + 1) % PIPESIZE) == p->readp){
if(p->readopen == 0)
if(p->readopen == 0){
release(&p->lock);
return -1;
release(&p->lock);
}
wakeup(&p->readp);
sleep(&p->writep);
acquire(&p->lock);
sleep(&p->writep, &p->lock);
}
p->data[p->writep] = addr[i];
p->writep = (p->writep + 1) % PIPESIZE;
}
release(&p->lock);
wakeup(&p->readp);
return i;
......@@ -101,19 +102,23 @@ pipe_read(struct pipe *p, char *addr, int n)
{
int i;
acquire(&p->lock);
while(p->readp == p->writep){
if(p->writeopen == 0)
if(p->writeopen == 0){
release(&p->lock);
return 0;
sleep(&p->readp);
}
sleep(&p->readp, &p->lock);
}
acquire(&p->lock);
for(i = 0; i < n; i++){
if(p->readp == p->writep)
break;
addr[i] = p->data[p->readp];
p->readp = (p->readp + 1) % PIPESIZE;
}
release(&p->lock);
wakeup(&p->writep);
return i;
......
proc.c
浏览文件 @ 46bbd72f
......@@ -95,7 +95,6 @@ newproc()
np->tf = (struct Trapframe *) (np->kstack + KSTACKSIZE - sizeof(struct Trapframe));
*(np->tf) = *(op->tf);
np->tf->tf_regs.reg_eax = 0; // so fork() returns 0 in child
cprintf("newproc pid=%d return to %x:%x tf-%p\n", np->pid, np->tf->tf_cs, np->tf->tf_eip, np->tf);
// set up new jmpbuf to start executing at trapret with esp pointing at tf
memset(&np->jmpbuf, 0, sizeof np->jmpbuf);
......@@ -109,8 +108,6 @@ newproc()
fd_reference(np->fds[fd]);
}
cprintf("newproc %x\n", np);
return np;
}
......@@ -126,18 +123,27 @@ scheduler(void)
setjmp(&cpus[cpu()].jmpbuf);
op = curproc[cpu()];
if(op == 0 || op->mtx != &proc_table_lock)
acquire1(&proc_table_lock, op);
if(op){
if(op->newstate <= 0 || op->newstate > ZOMBIE)
panic("scheduler");
op->state = op->newstate;
op->newstate = -1;
if(op->mtx){
struct spinlock *mtx = op->mtx;
op->mtx = 0;
if(mtx != &proc_table_lock)
release1(mtx, op);
}
}
// find a runnable process and switch to it
curproc[cpu()] = 0;
np = cpus[cpu()].lastproc + 1;
while(1){
acquire(&proc_table_lock);
for(i = 0; i < NPROC; i++){
if(np >= &proc[NPROC])
np = &proc[0];
......@@ -148,11 +154,13 @@ scheduler(void)
if(i < NPROC){
np->state = RUNNING;
release(&proc_table_lock);
release1(&proc_table_lock, op);
break;
}
release(&proc_table_lock);
release1(&proc_table_lock, op);
op = 0;
acquire(&proc_table_lock);
np = &proc[0];
}
......@@ -180,36 +188,56 @@ void
swtch(int newstate)
{
struct proc *p = curproc[cpu()];
if(p == 0)
panic("swtch no proc");
if(p->locks != 0)
if(p->mtx == 0 && p->locks != 0)
panic("swtch w/ locks");
if(p->mtx && p->locks != 1)
panic("swtch w/ locks 1");
if(p->mtx && p->mtx->locked == 0)
panic("switch w/ lock but not held");
if(p->locks && (read_eflags() & FL_IF))
panic("swtch w/ lock but FL_IF");
p->newstate = newstate; // basically an argument to scheduler()
if(setjmp(&p->jmpbuf) == 0)
longjmp(&cpus[cpu()].jmpbuf);
}
void
sleep(void *chan)
sleep(void *chan, struct spinlock *mtx)
{
struct proc *p = curproc[cpu()];
if(p == 0)
panic("sleep");
p->chan = chan;
p->mtx = mtx; // scheduler will release it
swtch(WAITING);
if(mtx)
acquire(mtx);
p->chan = 0;
}
void
wakeup(void *chan)
wakeup1(void *chan)
{
struct proc *p;
acquire(&proc_table_lock);
for(p = proc; p < &proc[NPROC]; p++){
if(p->state == WAITING && p->chan == chan){
for(p = proc; p < &proc[NPROC]; p++)
if(p->state == WAITING && p->chan == chan)
p->state = RUNNABLE;
}
}
}
void
wakeup(void *chan)
{
acquire(&proc_table_lock);
wakeup1(chan);
release(&proc_table_lock);
}
......@@ -229,8 +257,6 @@ proc_exit()
struct proc *cp = curproc[cpu()];
int fd;
cprintf("exit %x pid %d ppid %d\n", cp, cp->pid, cp->ppid);
for(fd = 0; fd < NOFILE; fd++){
if(cp->fds[fd]){
fd_close(cp->fds[fd]);
......@@ -243,32 +269,35 @@ proc_exit()
// wake up parent
for(p = proc; p < &proc[NPROC]; p++)
if(p->pid == cp->ppid)
wakeup(p);
wakeup1(p);
// abandon children
for(p = proc; p < &proc[NPROC]; p++)
if(p->ppid == cp->pid)
p->pid = 1;
release(&proc_table_lock);
// switch into scheduler
cp->mtx = &proc_table_lock;
swtch(ZOMBIE);
panic("a zombie revived");
}
// disable interrupts
void
cli(void)
{
cpus[cpu()].clis += 1;
if(cpus[cpu()].clis == 1)
if(cpus[cpu()].clis == 0)
__asm __volatile("cli");
cpus[cpu()].clis += 1;
if((read_eflags() & FL_IF) != 0)
panic("cli but enabled");
}
// enable interrupts
void
sti(void)
{
if((read_eflags() & FL_IF) != 0)
panic("sti but enabled");
if(cpus[cpu()].clis < 1)
panic("sti");
cpus[cpu()].clis -= 1;
......
proc.h
浏览文件 @ 46bbd72f
......@@ -41,6 +41,7 @@ struct proc{
char *kstack; // kernel stack, separate from mem so it doesn't move
enum proc_state state;
enum proc_state newstate; // desired state after swtch()
struct spinlock *mtx; // mutex for condition variable
int pid;
int ppid;
void *chan; // sleep
......
spinlock.c
浏览文件 @ 46bbd72f
......@@ -8,36 +8,20 @@
#define DEBUG 0
extern use_printf_lock;
extern int use_console_lock;
int getcallerpc(void *v) {
return ((int*)v)[-1];
}
void
acquire(struct spinlock * lock)
acquire1(struct spinlock * lock, struct proc *cp)
{
struct proc *cp = curproc[cpu()];
unsigned who;
if(cp)
who = (unsigned) cp;
else
who = cpu() + 1;
if(DEBUG) cprintf("cpu%d: acquiring at %x\n", cpu(), getcallerpc(&lock));
if (lock->who == who && lock->locked){
lock->count += 1;
} else {
cli();
// if we get the lock, eax will be zero
// if we don't get the lock, eax will be one
while ( cmpxchg(0, 1, &lock->locked) == 1 ) { ; }
lock->locker_pc = getcallerpc(&lock);
lock->count = 1;
lock->who = who;
}
cli();
while ( cmpxchg(0, 1, &lock->locked) == 1 ) { ; }
lock->locker_pc = getcallerpc(&lock);
if(cp)
cp->locks += 1;
......@@ -46,27 +30,29 @@ acquire(struct spinlock * lock)
}
void
release(struct spinlock * lock)
release1(struct spinlock * lock, struct proc *cp)
{
struct proc *cp = curproc[cpu()];
unsigned who;
if(cp)
who = (unsigned) cp;
else
who = cpu() + 1;
if(DEBUG) cprintf ("cpu%d: releasing at %x\n", cpu(), getcallerpc(&lock));
if(lock->who != who || lock->count < 1 || lock->locked != 1)
if(lock->locked != 1)
panic("release");
lock->count -= 1;
if(cp)
cp->locks -= 1;
if(lock->count < 1){
lock->who = 0;
cmpxchg(1, 0, &lock->locked);
sti();
}
cmpxchg(1, 0, &lock->locked);
sti();
}
void
acquire(struct spinlock *lock)
{
acquire1(lock, curproc[cpu()]);
}
void
release(struct spinlock *lock)
{
release1(lock, curproc[cpu()]);
}
spinlock.h
浏览文件 @ 46bbd72f
struct spinlock {
unsigned int locked;
unsigned who;
int count;
unsigned locker_pc;
};
syscall.c
浏览文件 @ 46bbd72f
......@@ -152,8 +152,12 @@ sys_fork()
struct proc *np;
np = newproc();
np->state = RUNNABLE;
return np->pid;
if(np){
np->state = RUNNABLE;
return np->pid;
} else {
return -1;
}
}
int
......@@ -170,11 +174,10 @@ sys_wait()
struct proc *cp = curproc[cpu()];
int any, pid;
cprintf("waid pid %d ppid %d\n", cp->pid, cp->ppid);
acquire(&proc_table_lock);
while(1){
any = 0;
acquire(&proc_table_lock);
for(p = proc; p < &proc[NPROC]; p++){
if(p->state == ZOMBIE && p->ppid == cp->pid){
kfree(p->mem, p->sz);
......@@ -182,18 +185,16 @@ sys_wait()
pid = p->pid;
p->state = UNUSED;
release(&proc_table_lock);
cprintf("%x collected %x\n", cp, p);
return pid;
}
if(p->state != UNUSED && p->ppid == cp->pid)
any = 1;
}
release(&proc_table_lock);
if(any == 0){
cprintf("%x nothing to wait for\n", cp);
release(&proc_table_lock);
return -1;
}
sleep(cp);
sleep(cp, &proc_table_lock);
}
}
......@@ -220,7 +221,7 @@ sys_block(void)
panic("couldn't start read\n");
}
cprintf("call sleep\n");
sleep (c);
sleep (c, 0);
if (ide_finish_read(c)) {
panic("couldn't do read\n");
}
......@@ -253,6 +254,17 @@ sys_kill()
return -1;
}
int
sys_panic()
{
struct proc *p = curproc[cpu()];
unsigned int addr;
fetcharg(0, &addr);
panic(p->mem + addr);
return 0;
}
void
syscall()
{
......@@ -292,6 +304,9 @@ syscall()
case SYS_kill:
ret = sys_kill();
break;
case SYS_panic:
ret = sys_panic();
break;
default:
cprintf("unknown sys call %d\n", num);
// XXX fault
......
syscall.h
浏览文件 @ 46bbd72f
......@@ -8,3 +8,4 @@
#define SYS_close 8
#define SYS_block 9
#define SYS_kill 10
#define SYS_panic 11
trap.c
浏览文件 @ 46bbd72f
......@@ -36,8 +36,14 @@ trap(struct Trapframe *tf)
{
int v = tf->tf_trapno;
if(cpus[cpu()].clis){
cprintf("cpu %d v %d eip %x\n", cpu(), v, tf->tf_eip);
panic("interrupt while interrupts are off");
}
if(v == T_SYSCALL){
struct proc *cp = curproc[cpu()];
int num = cp->tf->tf_regs.reg_eax;
if(cp == 0)
panic("syscall with no proc");
if(cp->killed)
......@@ -50,6 +56,14 @@ trap(struct Trapframe *tf)
panic("trap ret but not RUNNING");
if(tf != cp->tf)
panic("trap ret wrong tf");
if(cp->locks){
cprintf("num=%d\n", num);
panic("syscall returning locks held");
}
if(cpus[cpu()].clis)
panic("syscall returning but clis != 0");
if((read_eflags() & FL_IF) == 0)
panic("syscall returning but FL_IF clear");
if(read_esp() < (unsigned)cp->kstack ||
read_esp() >= (unsigned)cp->kstack + KSTACKSIZE)
panic("trap ret esp wrong");
......@@ -61,14 +75,20 @@ trap(struct Trapframe *tf)
if(v == (IRQ_OFFSET + IRQ_TIMER)){
struct proc *cp = curproc[cpu()];
lapic_timerintr();
if(cp && cp->locks)
panic("timer interrupt while holding a lock");
if(cp){
if(cpus[cpu()].clis != 0)
panic("trap clis > 0");
#if 1
if((read_eflags() & FL_IF) == 0)
panic("timer interrupt but interrupts now disabled");
#else
cpus[cpu()].clis += 1;
sti();
#endif
if(cp->killed)
proc_exit();
yield();
if(cp->state == RUNNING)
yield();
}
return;
}
......
usertests.c
浏览文件 @ 46bbd72f
......@@ -16,7 +16,7 @@ pipe1()
for(i = 0; i < 1033; i++)
buf[i] = seq++;
if(write(fds[1], buf, 1033) != 1033){
puts("pipe1 oops 1\n");
panic("pipe1 oops 1\n");
exit(1);
}
}
......@@ -31,7 +31,7 @@ pipe1()
break;
for(i = 0; i < n; i++){
if((buf[i] & 0xff) != (seq++ & 0xff)){
puts("pipe1 oops 2\n");
panic("pipe1 oops 2\n");
return;
}
}
......@@ -41,8 +41,9 @@ pipe1()
cc = sizeof(buf);
}
if(total != 5 * 1033)
puts("pipe1 oops 3\n");
panic("pipe1 oops 3\n");
close(fds[0]);
wait();
}
puts("pipe1 ok\n");
}
......@@ -69,7 +70,7 @@ preempt()
if(pid3 == 0){
close(pfds[0]);
if(write(pfds[1], "x", 1) != 1)
puts("preempt write error");
panic("preempt write error");
close(pfds[1]);
while(1)
;
......@@ -77,7 +78,7 @@ preempt()
close(pfds[1]);
if(read(pfds[0], buf, sizeof(buf)) != 1){
puts("preempt read error");
panic("preempt read error");
return;
}
close(pfds[0]);
......@@ -90,12 +91,37 @@ preempt()
puts("preempt ok\n");
}
// try to find any races between exit and wait
void
exitwait()
{
int i, pid;
for(i = 0; i < 100; i++){
pid = fork();
if(pid < 0){
panic("fork failed\n");
return;
}
if(pid){
if(wait() != pid){
panic("wait wrong pid\n");
return;
}
} else {
exit(0);
}
}
puts("exitwait ok\n");
}
main()
{
puts("usertests starting\n");
pipe1();
//preempt();
preempt();
exitwait();
while(1)
;
panic("usertests finished successfuly");
}
usys.S
浏览文件 @ 46bbd72f
......@@ -18,3 +18,4 @@ STUB(write)
STUB(close)
STUB(block)
STUB(kill)
STUB(panic)
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