sanchayanmaity/xv6-cs450
1
0
Fork 0
Code Issues Pull requests Packages Projects Releases Wiki Activity

no more big kernel lock

Browse source 
succeeds at usertests.c pipe test
This commit is contained in:
rtm 2006-07-12 01:48:35 +00:00
parent b41b38d0da
commit 4e8f237be8
15 changed files with 202 additions and 95 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

49
Notes
View file

@ -85,17 +85,44 @@ test pipe reader closes then write
test two readers, two writers.
test children being inherited by grandparent &c
kill
sleep()ing for something
running at user level
running in kernel
ooh, the relevant CPU may never get a clock interrupt
should each cpu have its own clock?
where to check?
loops around sleep()
return from any trap
rules about being killed deep inside a system call
test above cases
some sleep()s should be interruptible by kill()
cli/sti in acquire/release should nest!
in case you acquire two locks
what would need fixing if we got rid of kernel_lock?
console output
proc_exit() needs lock on proc *array* to deallocate
kill() needs lock on proc *array*
allocator's free list
global fd table (really free-ness)
sys_close() on fd table
fork on proc list, also next pid
hold lock until public slots in proc struct initialized
locks
init_lock
sequences CPU startup
proc_table_lock
also protects next_pid
per-fd lock *just* protects count read-modify-write
also maybe freeness?
memory allocator
printf
wakeup needs proc_table_lock
so we need recursive locks?
or you must hold the lock to call wakeup?
if locks contain proc *, they can't be used at interrupt time
only proc_table_lock will be used at interrupt time?
maybe it doesn't matter if we use curproc?
in general, the table locks protect both free-ness and
public variables of table elements
in many cases you can use table elements w/o a lock
e.g. if you are the process, or you are using an fd
why can't i get a lock in console code?
always triple fault
lock code shouldn't call cprintf...

7
console.c
View file

@ -1,6 +1,9 @@
#include <types.h>
#include <x86.h>
#include "defs.h"
#include "spinlock.h"
struct spinlock console_lock;
/*
* copy console output to parallel port, which you can tell
@ -26,6 +29,8 @@ cons_putc(int c)
unsigned short *crt = (unsigned short *) 0xB8000; // base of CGA memory
int ind;
//acquire(&console_lock);
lpt_putc(c);
// cursor position, 16 bits, col + 80*row
@ -56,6 +61,8 @@ cons_putc(int c)
outb(crtport + 1, ind >> 8);
outb(crtport, 15);
outb(crtport + 1, ind);
//release(&console_lock);
}
void

10
defs.h
View file

@ -13,7 +13,7 @@ struct proc;
struct jmpbuf;
void setupsegs(struct proc *);
struct proc * newproc(void);
void swtch(void);
void swtch(int);
void sleep(void *);
void wakeup(void *);
void scheduler(void);
@ -55,10 +55,9 @@ void lapic_enableintr(void);
void lapic_disableintr(void);
// spinlock.c
extern uint32_t kernel_lock;
void acquire_spinlock(uint32_t* lock);
void release_spinlock(uint32_t* lock);
void release_grant_spinlock(uint32_t* lock, int cpu);
struct spinlock;
void acquire(struct spinlock * lock);
void release(struct spinlock * lock);
// main.c
void load_icode(struct proc *p, uint8_t *binary, unsigned size);
@ -77,6 +76,7 @@ struct fd * fd_alloc();
void fd_close(struct fd *);
int fd_read(struct fd *fd, char *addr, int n);
int fd_write(struct fd *fd, char *addr, int n);
void fd_reference(struct fd *fd);
// ide.c
void ide_init(void);

25
fd.c
View file

@ -5,6 +5,9 @@
#include "proc.h"
#include "defs.h"
#include "fd.h"
#include "spinlock.h"
struct spinlock fd_table_lock;
struct fd fds[NFD];
@ -22,18 +25,24 @@ fd_ualloc()
return -1;
}
/*
* allocate a file descriptor structure
*/
struct fd *
fd_alloc()
{
int i;
acquire(&fd_table_lock);
for(i = 0; i < NFD; i++){
if(fds[i].type == FD_CLOSED){
fds[i].type = FD_NONE;
fds[i].count = 1;
release(&fd_table_lock);
return fds + i;
}
}
release(&fd_table_lock);
return 0;
}
@ -69,8 +78,11 @@ fd_read(struct fd *fd, char *addr, int n)
void
fd_close(struct fd *fd)
{
acquire(&fd_table_lock);
if(fd->count < 1 || fd->type == FD_CLOSED)
panic("fd_close");
fd->count -= 1;
if(fd->count == 0){
@ -79,6 +91,19 @@ fd_close(struct fd *fd)
} else {
panic("fd_close");
}
fd->count = 0;
fd->type = FD_CLOSED;
}
release(&fd_table_lock);
}
void
fd_reference(struct fd *fd)
{
acquire(&fd_table_lock);
if(fd->count < 1 || fd->type == FD_CLOSED)
panic("fd_reference");
fd->count += 1;
release(&fd_table_lock);
}

19
kalloc.c
View file

@ -10,6 +10,9 @@
#include "param.h"
#include "types.h"
#include "defs.h"
#include "spinlock.h"
struct spinlock kalloc_lock;
struct run {
struct run *next;
@ -54,6 +57,8 @@ kfree(char *cp, int len)
for(i = 0; i < len; i++)
cp[i] = 1;
acquire(&kalloc_lock);
rr = &freelist;
while(*rr){
struct run *rend = (struct run *) ((char *)(*rr) + (*rr)->len);
@ -63,13 +68,13 @@ kfree(char *cp, int len)
p->len = len + (*rr)->len;
p->next = (*rr)->next;
*rr = p;
return;
goto out;
}
if(pend < *rr){
p->len = len;
p->next = *rr;
*rr = p;
return;
goto out;
}
if(p == rend){
(*rr)->len += len;
@ -77,13 +82,16 @@ kfree(char *cp, int len)
(*rr)->len += (*rr)->next->len;
(*rr)->next = (*rr)->next->next;
}
return;
goto out;
}
rr = &((*rr)->next);
}
p->len = len;
p->next = 0;
*rr = p;
out:
release(&kalloc_lock);
}
/*
@ -99,20 +107,25 @@ kalloc(int n)
if(n % PAGE)
panic("kalloc");
acquire(&kalloc_lock);
rr = &freelist;
while(*rr){
struct run *r = *rr;
if(r->len == n){
*rr = r->next;
release(&kalloc_lock);
return (char *) r;
}
if(r->len > n){
char *p = (char *)r + (r->len - n);
r->len -= n;
release(&kalloc_lock);
return p;
}
rr = &(*rr)->next;
}
release(&kalloc_lock);
return 0;
}

12
main.c
View file

@ -15,8 +15,6 @@ extern char _binary_user1_start[], _binary_user1_size[];
extern char _binary_usertests_start[], _binary_usertests_size[];
extern char _binary_userfs_start[], _binary_userfs_size[];
char buf[512];
int
main()
{
@ -24,8 +22,6 @@ main()
if (acpu) {
cprintf("an application processor\n");
release_spinlock(&kernel_lock);
acquire_spinlock(&kernel_lock);
idtinit(); // CPU's idt
lapic_init(cpu());
lapic_timerinit();
@ -39,7 +35,6 @@ main()
cprintf("\nxV6\n\n");
pic_init(); // initialize PIC
mp_init(); // multiprocessor
kinit(); // physical memory allocator
tvinit(); // trap vectors
idtinit(); // CPU's idt
@ -61,11 +56,14 @@ main()
p->ppid = 0;
setupsegs(p);
mp_init(); // multiprocessor
// turn on timer and enable interrupts on the local APIC
lapic_timerinit();
lapic_enableintr();
// init disk device
ide_init();
//ide_init();
// become interruptable
sti();
@ -74,7 +72,9 @@ main()
load_icode(p, _binary_usertests_start, (unsigned) _binary_usertests_size);
//load_icode(p, _binary_userfs_start, (unsigned) _binary_userfs_size);
p->state = RUNNABLE;
cprintf("loaded userfs\n");
scheduler();
return 0;

4
mp.c
View file

@ -391,15 +391,11 @@ mp_init()
memmove((void *) APBOOTCODE,_binary_bootother_start,
(uint32_t) _binary_bootother_size);
acquire_spinlock(&kernel_lock);
for(c = 0; c < ncpu; c++){
if (cpus+c == bcpu) continue;
cprintf ("starting processor %d\n", c);
release_grant_spinlock(&kernel_lock, c);
*(unsigned *)(APBOOTCODE-4) = (unsigned) (cpus[c].mpstack) + MPSTACK; // tell it what to use for %esp
*(unsigned *)(APBOOTCODE-8) = (unsigned)&main; // tell it where to jump to
lapic_startap(cpus + c, (uint32_t) APBOOTCODE);
acquire_spinlock(&kernel_lock);
cprintf ("done starting processor %d\n", c);
}
}

10
pipe.c
View file

@ -5,6 +5,7 @@
#include "proc.h"
#include "defs.h"
#include "fd.h"
#include "spinlock.h"
#define PIPESIZE 512
@ -13,6 +14,7 @@ struct pipe {
int writeopen; // write fd is still open
int writep; // next index to write
int readp; // next index to read
struct spinlock lock;
char data[PIPESIZE];
};
@ -32,6 +34,7 @@ pipe_alloc(struct fd **fd1, struct fd **fd2)
p->writeopen = 1;
p->writep = 0;
p->readp = 0;
memset(&p->lock, 0, sizeof(p->lock));
(*fd1)->type = FD_PIPE;
(*fd1)->readable = 1;
(*fd1)->writeable = 0;
@ -74,16 +77,21 @@ pipe_write(struct pipe *p, char *addr, int n)
{
int i;
acquire(&p->lock);
for(i = 0; i < n; i++){
while(((p->writep + 1) % PIPESIZE) == p->readp){
if(p->readopen == 0)
return -1;
release(&p->lock);
wakeup(&p->readp);
sleep(&p->writep);
acquire(&p->lock);
}
p->data[p->writep] = addr[i];
p->writep = (p->writep + 1) % PIPESIZE;
}
release(&p->lock);
wakeup(&p->readp);
return i;
}
@ -99,12 +107,14 @@ pipe_read(struct pipe *p, char *addr, int n)
sleep(&p->readp);
}
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;
}

67
proc.c
View file

@ -5,6 +5,9 @@
#include "fd.h"
#include "proc.h"
#include "defs.h"
#include "spinlock.h"
struct spinlock proc_table_lock;
struct proc proc[NPROC];
struct proc *curproc[NCPU];
@ -43,6 +46,7 @@ extern void trapret();
/*
* internal fork(). does not copy kernel stack; instead,
* sets up the stack to return as if from system call.
* caller must set state to RUNNABLE.
*/
struct proc *
newproc()
@ -51,11 +55,18 @@ newproc()
struct proc *op;
int fd;
for(np = &proc[1]; np < &proc[NPROC]; np++)
if(np->state == UNUSED)
acquire(&proc_table_lock);
for(np = &proc[1]; np < &proc[NPROC]; np++){
if(np->state == UNUSED){
np->state = EMBRYO;
break;
if(np >= &proc[NPROC])
}
}
if(np >= &proc[NPROC]){
release(&proc_table_lock);
return 0;
}
// copy from proc[0] if we're bootstrapping
op = curproc[cpu()];
@ -64,6 +75,9 @@ newproc()
np->pid = next_pid++;
np->ppid = op->pid;
release(&proc_table_lock);
np->sz = op->sz;
np->mem = kalloc(op->sz);
if(np->mem == 0)
@ -72,6 +86,7 @@ newproc()
np->kstack = kalloc(KSTACKSIZE);
if(np->kstack == 0){
kfree(np->mem, op->sz);
np->state = UNUSED;
return 0;
}
setupsegs(np);
@ -91,11 +106,9 @@ newproc()
for(fd = 0; fd < NOFILE; fd++){
np->fds[fd] = op->fds[fd];
if(np->fds[fd])
np->fds[fd]->count += 1;
fd_reference(np->fds[fd]);
}
np->state = RUNNABLE;
cprintf("newproc %x\n", np);
return np;
@ -111,11 +124,20 @@ scheduler(void)
cpus[cpu()].lastproc = &proc[0];
setjmp(&cpus[cpu()].jmpbuf);
op = curproc[cpu()];
if(op){
if(op->newstate <= 0 || op->newstate > ZOMBIE)
panic("scheduler");
op->state = op->newstate;
op->newstate = -1;
}
// 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];
@ -123,20 +145,20 @@ scheduler(void)
break;
np++;
}
if(i < NPROC)
if(i < NPROC){
np->state = RUNNING;
release(&proc_table_lock);
break;
// cprintf("swtch %d: nothing to run %d %d\n",
// cpu(), proc[1].state, proc[2].state);
release_spinlock(&kernel_lock);
acquire_spinlock(&kernel_lock);
}
release(&proc_table_lock);
np = &proc[0];
}
cpus[cpu()].lastproc = np;
curproc[cpu()] = np;
np->state = RUNNING;
// h/w sets busy bit in TSS descriptor sometimes, and faults
// if it's set in LTR. so clear tss descriptor busy bit.
np->gdt[SEG_TSS].sd_type = STS_T32A;
@ -155,11 +177,12 @@ scheduler(void)
// give up the cpu by switching to the scheduler,
// which runs on the per-cpu stack.
void
swtch(void)
swtch(int newstate)
{
struct proc *p = curproc[cpu()];
if(p == 0)
panic("swtch");
p->newstate = newstate; // basically an argument to scheduler()
if(setjmp(&p->jmpbuf) == 0)
longjmp(&cpus[cpu()].jmpbuf);
}
@ -171,8 +194,7 @@ sleep(void *chan)
if(p == 0)
panic("sleep");
p->chan = chan;
p->state = WAITING;
swtch();
swtch(WAITING);
}
void
@ -180,9 +202,11 @@ wakeup(void *chan)
{
struct proc *p;
acquire(&proc_table_lock);
for(p = proc; p < &proc[NPROC]; p++)
if(p->state == WAITING && p->chan == chan)
p->state = RUNNABLE;
release(&proc_table_lock);
}
// give up the CPU but stay marked as RUNNABLE
@ -191,8 +215,7 @@ yield()
{
if(curproc[cpu()] == 0 || curproc[cpu()]->state != RUNNING)
panic("yield");
curproc[cpu()]->state = RUNNABLE;
swtch();
swtch(RUNNABLE);
}
void
@ -211,7 +234,7 @@ proc_exit()
}
}
cp->state = ZOMBIE;
acquire(&proc_table_lock);
// wake up parent
for(p = proc; p < &proc[NPROC]; p++)
@ -223,6 +246,8 @@ proc_exit()
if(p->ppid == cp->pid)
p->pid = 1;
acquire(&proc_table_lock);
// switch into scheduler
swtch();
swtch(ZOMBIE);
}

5
proc.h
View file

@ -33,11 +33,14 @@ struct jmpbuf {
int jb_eip;
};
enum proc_state { UNUSED, EMBRYO, WAITING, RUNNABLE, RUNNING, ZOMBIE };
struct proc{
char *mem; // start of process's physical memory
unsigned sz; // total size of mem, including kernel stack
char *kstack; // kernel stack, separate from mem so it doesn't move
enum { UNUSED, RUNNABLE, WAITING, ZOMBIE, RUNNING } state;
enum proc_state state;
enum proc_state newstate; // desired state after swtch()
int pid;
int ppid;
void *chan; // sleep

61
spinlock.c
View file

@ -2,51 +2,50 @@
#include "defs.h"
#include "x86.h"
#include "mmu.h"
#include "param.h"
#include "proc.h"
#include "spinlock.h"
#define LOCK_FREE -1
#define DEBUG 0
uint32_t kernel_lock = LOCK_FREE;
int getcallerpc(void *v) {
return ((int*)v)[-1];
}
// lock = LOCK_FREE if free, else = cpu_id of owner CPU
void
acquire_spinlock(uint32_t* lock)
acquire(struct spinlock * lock)
{
int cpu_id = cpu();
struct proc * cp = curproc[cpu()];
// on a real machine there would be a memory barrier here
if(DEBUG) cprintf("cpu%d: acquiring at %x\n", cpu_id, getcallerpc(&lock));
cli();
if (*lock == cpu_id)
panic("recursive lock");
while ( cmpxchg(LOCK_FREE, cpu_id, lock) != cpu_id ) { ; }
if(DEBUG) cprintf("cpu%d: acquired at %x\n", cpu_id, getcallerpc(&lock));
if(DEBUG) cprintf("cpu%d: acquiring at %x\n", cpu(), getcallerpc(&lock));
if (cp && lock->p == cp && lock->locked){
lock->count += 1;
} else {
cli();
while ( cmpxchg(0, 1, &lock->locked) != 1 ) { ; }
lock->locker_pc = getcallerpc(&lock);
lock->count = 1;
lock->p = cp;
}
if(DEBUG) cprintf("cpu%d: acquired at %x\n", cpu(), getcallerpc(&lock));
}
void
release_spinlock(uint32_t* lock)
release(struct spinlock * lock)
{
int cpu_id = cpu();
if(DEBUG) cprintf ("cpu%d: releasing at %x\n", cpu_id, getcallerpc(&lock));
if (*lock != cpu_id)
panic("release_spinlock: releasing a lock that i don't own\n");
*lock = LOCK_FREE;
// on a real machine there would be a memory barrier here
sti();
}
struct proc * cp = curproc[cpu()];
void
release_grant_spinlock(uint32_t* lock, int c)
{
int cpu_id = cpu();
if(DEBUG) cprintf ("cpu%d: release_grant to %d at %x\n", cpu_id, c, getcallerpc(&lock));
if (*lock != cpu_id)
panic("release_spinlock: releasing a lock that i don't own\n");
*lock = c;
}
if(DEBUG) cprintf ("cpu%d: releasing at %x\n", cpu(), getcallerpc(&lock));
if(lock->p != cp || lock->count < 1 || lock->locked != 1)
panic("release");
lock->count -= 1;
if(lock->count < 1){
lock->p = 0;
cmpxchg(1, 0, &lock->locked);
sti();
// on a real machine there would be a memory barrier here
}
}

10
syscall.c
View file

@ -6,6 +6,7 @@
#include "x86.h"
#include "traps.h"
#include "syscall.h"
#include "spinlock.h"
/*
* User code makes a system call with INT T_SYSCALL.
@ -18,6 +19,8 @@
* Return value? Error indication? Errno?
*/
extern struct spinlock proc_table_lock;
/*
* fetch 32 bits from a user-supplied pointer.
* returns 1 if addr was OK, 0 if illegal.
@ -149,6 +152,7 @@ sys_fork()
struct proc *np;
np = newproc();
np->state = RUNNABLE;
return np->pid;
}
@ -170,18 +174,21 @@ sys_wait()
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);
kfree(p->kstack, KSTACKSIZE);
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);
return -1;
@ -232,14 +239,17 @@ sys_kill()
struct proc *p;
fetcharg(0, &pid);
acquire(&proc_table_lock);
for(p = proc; p < &proc[NPROC]; p++){
if(p->pid == pid && p->state != UNUSED){
p->killed = 1;
if(p->state == WAITING)
p->state = RUNNABLE;
release(&proc_table_lock);
return 0;
}
}
release(&proc_table_lock);
return -1;
}

10
trap.c
View file

@ -5,6 +5,7 @@
#include "defs.h"
#include "x86.h"
#include "traps.h"
#include "syscall.h"
struct Gatedesc idt[256];
struct Pseudodesc idt_pd = { 0, sizeof(idt) - 1, (unsigned) &idt };
@ -35,12 +36,6 @@ trap(struct Trapframe *tf)
{
int v = tf->tf_trapno;
if(tf->tf_cs == 0x8 && kernel_lock == cpu())
cprintf("cpu %d: trap %d from %x:%x with lock=%d\n",
cpu(), v, tf->tf_cs, tf->tf_eip, kernel_lock);
acquire_spinlock(&kernel_lock); // released in trapret in trapasm.S
if(v == T_SYSCALL){
struct proc *cp = curproc[cpu()];
if(cp == 0)
@ -55,7 +50,8 @@ trap(struct Trapframe *tf)
panic("trap ret but not RUNNING");
if(tf != cp->tf)
panic("trap ret wrong tf");
if(read_esp() < (unsigned)cp->kstack || read_esp() >= (unsigned)cp->kstack + KSTACKSIZE)
if(read_esp() < (unsigned)cp->kstack ||
read_esp() >= (unsigned)cp->kstack + KSTACKSIZE)
panic("trap ret esp wrong");
if(cp->killed)
proc_exit();

4
trapasm.S
View file

@ -22,10 +22,6 @@ alltraps:
* expects ESP to point to a Trapframe
*/
trapret:
pushl $kernel_lock
call release_spinlock
addl $0x4, %esp
popal
popl %es
popl %ds

4
usertests.c
View file

@ -93,8 +93,8 @@ preempt()
main()
{
puts("usertests starting\n");
//pipe1();
preempt();
pipe1();
//preempt();
while(1)
;