diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/proc.c | 29 |
1 files changed, 15 insertions, 14 deletions
diff --git a/kernel/proc.c b/kernel/proc.c index bd77dad..22e7ce4 100644 --- a/kernel/proc.c +++ b/kernel/proc.c @@ -20,10 +20,11 @@ static void freeproc(struct proc *p); extern char trampoline[]; // trampoline.S -// protects parent/child relationships. -// must be held when using p->parent. +// helps ensure that wakeups of wait()ing +// parents are not lost. helps obey the +// memory model when using p->parent. // must be acquired before any p->lock. -struct spinlock proc_tree_lock; +struct spinlock wait_lock; // Allocate a page for each process's kernel stack. // Map it high in memory, followed by an invalid @@ -48,7 +49,7 @@ procinit(void) struct proc *p; initlock(&pid_lock, "nextpid"); - initlock(&proc_tree_lock, "proc_tree"); + initlock(&wait_lock, "wait_lock"); for(p = proc; p < &proc[NPROC]; p++) { initlock(&p->lock, "proc"); p->kstack = KSTACK((int) (p - proc)); @@ -306,9 +307,9 @@ fork(void) release(&np->lock); - acquire(&proc_tree_lock); + acquire(&wait_lock); np->parent = p; - release(&proc_tree_lock); + release(&wait_lock); acquire(&np->lock); np->state = RUNNABLE; @@ -318,7 +319,7 @@ fork(void) } // Pass p's abandoned children to init. -// Caller must hold proc_tree_lock. +// Caller must hold wait_lock. void reparent(struct proc *p) { @@ -357,7 +358,7 @@ exit(int status) end_op(); p->cwd = 0; - acquire(&proc_tree_lock); + acquire(&wait_lock); // Give any children to init. reparent(p); @@ -370,7 +371,7 @@ exit(int status) p->xstate = status; p->state = ZOMBIE; - release(&proc_tree_lock); + release(&wait_lock); // Jump into the scheduler, never to return. sched(); @@ -386,7 +387,7 @@ wait(uint64 addr) int havekids, pid; struct proc *p = myproc(); - acquire(&proc_tree_lock); + acquire(&wait_lock); for(;;){ // Scan through table looking for exited children. @@ -403,12 +404,12 @@ wait(uint64 addr) if(addr != 0 && copyout(p->pagetable, addr, (char *)&np->xstate, sizeof(np->xstate)) < 0) { release(&np->lock); - release(&proc_tree_lock); + release(&wait_lock); return -1; } freeproc(np); release(&np->lock); - release(&proc_tree_lock); + release(&wait_lock); return pid; } release(&np->lock); @@ -417,12 +418,12 @@ wait(uint64 addr) // No point waiting if we don't have any children. if(!havekids || p->killed){ - release(&proc_tree_lock); + release(&wait_lock); return -1; } // Wait for a child to exit. - sleep(p, &proc_tree_lock); //DOC: wait-sleep + sleep(p, &wait_lock); //DOC: wait-sleep } } |