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xv6-cs450
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Some proc cleanup, moving some of copyproc into allocproc. 

Also, an experiment: use "thread-local" storage for c and cp
instead of the #define macro for curproc[cpu()].
This commit is contained in:
rsc 2009-05-31 00:28:45 +00:00
parent 0c7f483838
commit 19333efb9e
9 changed files with 147 additions and 118 deletions
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4
Makefile
View File

@ -23,6 +23,7 @@ OBJS = \
timer.o\
trapasm.o\
trap.o\
uart.o\
vectors.o\
# Cross-compiling (e.g., on Mac OS X)
@ -139,6 +140,9 @@ bochs : fs.img xv6.img
qemu: fs.img xv6.img
qemu -parallel stdio -hdb fs.img xv6.img
qemutty: fs.img xv6.img
qemu -nographic -smp 2 -hdb fs.img xv6.img
# CUT HERE
# prepare dist for students
# after running make dist, probably want to

11
defs.h
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@ -73,6 +73,7 @@ extern volatile uint* lapic;
void lapiceoi(void);
void lapicinit(int);
void lapicstartap(uchar, uint);
void microdelay(int);
// mp.c
extern int ismp;
@ -92,14 +93,14 @@ int pipewrite(struct pipe*, char*, int);
// proc.c
struct proc* copyproc(struct proc*);
struct proc* curproc(void);
void exit(void);
int growproc(int);
int kill(int);
void pinit(void);
void procdump(void);
void scheduler(void) __attribute__((noreturn));
void setupsegs(struct proc*);
void ksegment(void);
void usegment(void);
void sleep(void*, struct spinlock*);
void userinit(void);
int wait(void);
@ -144,6 +145,12 @@ extern int ticks;
void tvinit(void);
extern struct spinlock tickslock;
// uart.c
void uartinit(void);
void uartintr(void);
void uartputc(int);
// number of elements in fixed-size array
#define NELEM(x) (sizeof(x)/sizeof((x)[0]))

2
exec.c
View File

@ -104,7 +104,7 @@ exec(char *path, char **argv)
cp->sz = sz;
cp->tf->eip = elf.entry; // main
cp->tf->esp = sp;
setupsegs(cp);
usegment();
return 0;
bad:

2
lapic.c
View File

@ -121,7 +121,7 @@ lapiceoi(void)
// Spin for a given number of microseconds.
// On real hardware would want to tune this dynamically.
static void
void
microdelay(int us)
{
volatile int j = 0;

27
main.c
View File

@ -5,6 +5,9 @@
#include "proc.h"
#include "x86.h"
__thread struct cpu *c;
__thread struct proc *cp;
static void bootothers(void);
static void mpmain(void) __attribute__((noreturn));
@ -14,20 +17,22 @@ main(void)
{
mpinit(); // collect info about this machine
lapicinit(mpbcpu());
ksegment();
picinit(); // interrupt controller
ioapicinit(); // another interrupt controller
consoleinit(); // I/O devices & their interrupts
uartinit(); // serial port
cprintf("\ncpu%d: starting xv6\n\n", cpu());
pinit(); // process table
binit(); // buffer cache
picinit(); // interrupt controller
ioapicinit(); // another interrupt controller
kinit(); // physical memory allocator
pinit(); // process table
tvinit(); // trap vectors
binit(); // buffer cache
fileinit(); // file table
iinit(); // inode cache
consoleinit(); // I/O devices & their interrupts
ideinit(); // disk
ideinit(); // disk
if(!ismp)
timerinit(); // uniprocessor timer
timerinit(); // uniprocessor timer
userinit(); // first user process
bootothers(); // start other processors
@ -40,12 +45,12 @@ main(void)
static void
mpmain(void)
{
cprintf("cpu%d: mpmain\n", cpu());
idtinit();
if(cpu() != mpbcpu())
lapicinit(cpu());
setupsegs(0);
xchg(&cpus[cpu()].booted, 1);
ksegment();
cprintf("cpu%d: mpmain\n", cpu());
idtinit();
xchg(&c->booted, 1);
cprintf("cpu%d: scheduling\n", cpu());
scheduler();

166
proc.c
View File

@ -36,16 +36,31 @@ allocproc(void)
if(p->state == UNUSED){
p->state = EMBRYO;
p->pid = nextpid++;
release(&proc_table_lock);
return p;
goto found;
}
}
release(&proc_table_lock);
return 0;
found:
release(&proc_table_lock);
// Allocate kernel stack if necessary.
if((p->kstack = kalloc(KSTACKSIZE)) == 0){
p->state = UNUSED;
return 0;
}
p->tf = (struct trapframe*)(p->kstack + KSTACKSIZE) - 1;
// Set up new context to start executing at forkret (see below).
p->context = (struct context *)p->tf - 1;
memset(p->context, 0, sizeof(*p->context));
p->context->eip = (uint)forkret;
return p;
}
// Grow current process's memory by n bytes.
// Return old size on success, -1 on failure.
// Return 0 on success, -1 on failure.
int
growproc(int n)
{
@ -59,37 +74,53 @@ growproc(int n)
kfree(cp->mem, cp->sz);
cp->mem = newmem;
cp->sz += n;
setupsegs(cp);
return cp->sz - n;
usegment();
return 0;
}
// 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.
// Set up CPU's kernel segment descriptors.
void
setupsegs(struct proc *p)
ksegment(void)
{
struct cpu *c;
struct cpu *c1;
c1 = &cpus[cpu()];
c1->gdt[0] = SEG_NULL;
c1->gdt[SEG_KCODE] = SEG(STA_X|STA_R, 0, 0x100000 + 64*1024-1, 0);
c1->gdt[SEG_KDATA] = SEG(STA_W, 0, 0xffffffff, 0);
c1->gdt[SEG_KCPU] = SEG(STA_W, (uint)&c1->tls+sizeof(c1->tls), 0xffffffff, 0);
c1->gdt[SEG_UCODE] = SEG_NULL;
c1->gdt[SEG_UDATA] = SEG_NULL;
c1->gdt[SEG_TSS] = SEG_NULL;
lgdt(c1->gdt, sizeof(c1->gdt));
// Initialize cpu-local variables.
setgs(SEG_KCPU << 3);
c = c1;
cp = 0;
}
// Set up CPU's segment descriptors and task state for the current process.
// If cp==0, set up for "idle" state for when scheduler() is running.
void
usegment(void)
{
pushcli();
c = &cpus[cpu()];
c->ts.ss0 = SEG_KDATA << 3;
if(p)
c->ts.esp0 = (uint)(p->kstack + KSTACKSIZE);
if(cp)
c->ts.esp0 = (uint)(cp->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);
if(cp){
c->gdt[SEG_UCODE] = SEG(STA_X|STA_R, (uint)cp->mem, cp->sz-1, DPL_USER);
c->gdt[SEG_UDATA] = SEG(STA_W, (uint)cp->mem, cp->sz-1, DPL_USER);
} else {
c->gdt[SEG_UCODE] = SEG_NULL;
c->gdt[SEG_UDATA] = SEG_NULL;
}
c->gdt[SEG_TSS] = SEG16(STS_T32A, (uint)&c->ts, sizeof(c->ts)-1, 0);
c->gdt[SEG_TSS].s = 0;
lgdt(c->gdt, sizeof(c->gdt));
ltr(SEG_TSS << 3);
@ -109,40 +140,23 @@ copyproc(struct proc *p)
if((np = allocproc()) == 0)
return 0;
// Allocate kernel stack.
if((np->kstack = kalloc(KSTACKSIZE)) == 0){
// Copy process state from p.
np->sz = p->sz;
if((np->mem = kalloc(np->sz)) == 0){
kfree(np->kstack, KSTACKSIZE);
np->kstack = 0;
np->state = UNUSED;
return 0;
}
np->tf = (struct trapframe*)(np->kstack + KSTACKSIZE) - 1;
memmove(np->mem, p->mem, np->sz);
np->parent = p;
*np->tf = *p->tf;
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;
np->parent = 0;
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);
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).
np->context = (struct context *)np->tf - 1;
memset(np->context, 0, sizeof(*np->context));
np->context->eip = (uint)forkret;
// Clear %eax so that fork system call returns 0 in child.
np->tf->eax = 0;
return np;
}
@ -153,10 +167,14 @@ userinit(void)
struct proc *p;
extern uchar _binary_initcode_start[], _binary_initcode_size[];
p = copyproc(0);
p = allocproc();
initproc = p;
// Initialize memory from initcode.S
p->sz = PAGE;
p->mem = kalloc(p->sz);
p->cwd = namei("/");
memmove(p->mem, _binary_initcode_start, (int)_binary_initcode_size);
memset(p->tf, 0, sizeof(*p->tf));
p->tf->cs = (SEG_UCODE << 3) | DPL_USER;
p->tf->ds = (SEG_UDATA << 3) | DPL_USER;
@ -164,30 +182,12 @@ userinit(void)
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;
p->tf->eip = 0; // beginning of initcode.S
// 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->cwd = namei("/");
p->state = RUNNABLE;
initproc = p;
}
// Return currently running process.
struct proc*
curproc(void)
{
struct proc *p;
pushcli();
p = cpus[cpu()].curproc;
popcli();
return p;
}
//PAGEBREAK: 42
@ -202,10 +202,8 @@ void
scheduler(void)
{
struct proc *p;
struct cpu *c;
int i;
c = &cpus[cpu()];
for(;;){
// Enable interrupts on this processor, in lieu of saving intena.
sti();
@ -220,15 +218,15 @@ scheduler(void)
// 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);
cp = p;
usegment();
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);
cp = 0;
usegment();
}
release(&proc_table_lock);
@ -236,7 +234,7 @@ scheduler(void)
}
// Enter scheduler. Must already hold proc_table_lock
// and have changed curproc[cpu()]->state.
// and have changed cp->state.
void
sched(void)
{
@ -248,12 +246,12 @@ sched(void)
panic("sched running");
if(!holding(&proc_table_lock))
panic("sched proc_table_lock");
if(cpus[cpu()].ncli != 1)
if(c->ncli != 1)
panic("sched locks");
intena = cpus[cpu()].intena;
swtch(&cp->context, &cpus[cpu()].context);
cpus[cpu()].intena = intena;
intena = c->intena;
swtch(&cp->context, &c->context);
c->intena = intena;
}
// Give up the CPU for one scheduling round.
@ -421,6 +419,7 @@ wait(void)
if(p->state == UNUSED)
continue;
if(p->parent == cp){
havekids = 1;
if(p->state == ZOMBIE){
// Found one.
kfree(p->mem, p->sz);
@ -433,7 +432,6 @@ wait(void)
release(&proc_table_lock);
return pid;
}
havekids = 1;
}
}

39
proc.h
View File

@ -1,17 +1,21 @@
// Segments in proc->gdt
// Segments in proc->gdt.
// Also known to bootasm.S and trapasm.S
#define SEG_KCODE 1 // kernel code
#define SEG_KDATA 2 // kernel data+stack
#define SEG_UCODE 3
#define SEG_UDATA 4
#define SEG_TSS 5 // this process's task state
#define NSEGS 6
#define SEG_KCPU 3 // kernel per-cpu data
#define SEG_UCODE 4
#define SEG_UDATA 5
#define SEG_TSS 6 // this process's task state
#define NSEGS 7
// Saved registers for kernel context switches.
// Don't need to save all the segment registers (%cs, etc),
// because they are constant across kernel contexts.
// Stack pointer is encoded in the address of context,
// which must be placed at the bottom of the stack.
// The layout of context must match code in swtch.S.
// Don't need to save %eax, %ecx, %edx, because the
// x86 convention is that the caller has saved them.
// Contexts are stored at the bottom of the stack they
// describe; the stack pointer is the address of the context.
// The layout of the context must match the code in swtch.S.
struct context {
uint edi;
uint esi;
@ -30,12 +34,12 @@ struct proc {
enum proc_state state; // Process state
int pid; // Process ID
struct proc *parent; // Parent process
struct trapframe *tf; // Trap frame for current syscall
struct context *context; // Switch here to run process
void *chan; // If non-zero, sleeping on chan
int killed; // If non-zero, have been killed
struct file *ofile[NOFILE]; // Open files
struct inode *cwd; // Current directory
struct context *context; // Switch here to run process
struct trapframe *tf; // Trap frame for current syscall
char name[16]; // Process name (debugging)
};
@ -48,18 +52,23 @@ struct proc {
// Per-CPU state
struct cpu {
uchar apicid; // Local APIC ID
struct proc *curproc; // Process currently running.
struct context *context; // Switch here to enter scheduler
struct taskstate ts; // Used by x86 to find stack for interrupt
struct segdesc gdt[NSEGS]; // x86 global descriptor table
volatile uint booted; // Has the CPU started?
int ncli; // Depth of pushcli nesting.
int intena; // Were interrupts enabled before pushcli?
int intena; // Were interrupts enabled before pushcli?
void *tls[2];
};
extern struct cpu cpus[NCPU];
extern int ncpu;
// "cp" is a short alias for curproc().
// It gets used enough to make this worthwhile.
#define cp curproc()
// Per-CPU variables, holding pointers to the
// current cpu and to the current process.
// The __thread prefix tells gcc to refer to them in the segment
// pointed at by gs; the name __thread derives from the use
// of the same mechanism to provide per-thread storage in
// multithreaded user programs.
extern __thread struct cpu *c; // This cpu.
extern __thread struct proc *cp; // Current process on this cpu.

8
spinlock.c
View File

@ -102,8 +102,8 @@ pushcli(void)
eflags = readeflags();
cli();
if(cpus[cpu()].ncli++ == 0)
cpus[cpu()].intena = eflags & FL_IF;
if(c->ncli++ == 0)
c->intena = eflags & FL_IF;
}
void
@ -111,9 +111,9 @@ popcli(void)
{
if(readeflags()&FL_IF)
panic("popcli - interruptible");
if(--cpus[cpu()].ncli < 0)
if(--c->ncli < 0)
panic("popcli");
if(cpus[cpu()].ncli == 0 && cpus[cpu()].intena)
if(c->ncli == 0 && c->intena)
sti();
}

6
x86.h
View File

@ -103,6 +103,12 @@ xchg(volatile uint *addr, uint newval)
return result;
}
static inline void
setgs(ushort gs)
{
asm volatile("movw %0, %%gs" : : "r" (gs));
}
static inline void
cli(void)
{