From 38084bcea84e79f5fff9ce8c7f91c077fc1eacd3 Mon Sep 17 00:00:00 2001
From: Robert Morris <rtm@csail.mit.edu>
Date: Thu, 5 Nov 2020 09:47:59 -0500
Subject: proc_tree_lock -> wait_lock
---
kernel/proc.c | 29 +++++++++++++++--------------
1 file changed, 15 insertions(+), 14 deletions(-)
(limited to 'kernel')
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
}
}
--
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