Imbus/xv6-riscv-kernel
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hold ptable.lock for the entire process creation

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however, processes still modify their own p->* without locking
This commit is contained in:
Robert Morris 2016-08-13 03:44:13 -04:00
parent 20d05d4411
commit 19f65413bd
2 changed files with 15 additions and 9 deletions
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20
proc.c
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@ -31,23 +31,21 @@ pinit(void)
// If found, change state to EMBRYO and initialize
// state required to run in the kernel.
// Otherwise return 0.
// Must hold ptable.lock.
static struct proc*
allocproc(void)
{
struct proc *p;
char *sp;
acquire(&ptable.lock);
for(p = ptable.proc; p < &ptable.proc[NPROC]; p++)
if(p->state == UNUSED)
goto found;
release(&ptable.lock);
return 0;
found:
p->state = EMBRYO;
p->pid = nextpid++;
release(&ptable.lock);
// Allocate kernel stack.
if((p->kstack = kalloc()) == 0){
@ -81,6 +79,8 @@ userinit(void)
struct proc *p;
extern char _binary_initcode_start[], _binary_initcode_size[];
acquire(&ptable.lock);
p = allocproc();
initproc = p;
if((p->pgdir = setupkvm()) == 0)
@ -100,6 +100,8 @@ userinit(void)
p->cwd = namei("/");
p->state = RUNNABLE;
release(&ptable.lock);
}
// Grow current process's memory by n bytes.
@ -131,15 +133,20 @@ fork(void)
int i, pid;
struct proc *np;
acquire(&ptable.lock);
// Allocate process.
if((np = allocproc()) == 0)
if((np = allocproc()) == 0){
release(&ptable.lock);
return -1;
}
// Copy process state from p.
if((np->pgdir = copyuvm(proc->pgdir, proc->sz)) == 0){
kfree(np->kstack);
np->kstack = 0;
np->state = UNUSED;
release(&ptable.lock);
return -1;
}
np->sz = proc->sz;
@ -158,9 +165,8 @@ fork(void)
pid = np->pid;
// lock to force the compiler to emit the np->state write last.
acquire(&ptable.lock);
np->state = RUNNABLE;
release(&ptable.lock);
return pid;
@ -233,11 +239,11 @@ wait(void)
kfree(p->kstack);
p->kstack = 0;
freevm(p->pgdir);
p->state = UNUSED;
p->pid = 0;
p->parent = 0;
p->name[0] = 0;
p->killed = 0;
p->state = UNUSED;
release(&ptable.lock);
return pid;
}