Return error from fork when we run out of stacks.

..running the GC and retrying doesn't usually help free up stacks. The parent thread needs to wait.

Return error from fork when we run out of stacks.
0bfacd12 · Silas Boyd-Wickizer · b72f261e · 0bfacd12
--- a/kernel/proc.cc
+++ b/kernel/proc.cc
@@ -86,8 +86,6 @@ proc::proc(int npid) :
 proc::~proc(void)
 {
  magic = 0;
-  if (kstack)
-    ksfree(slab_stack, kstack);
  destroylock(&lock);
  destroycondvar(&cv);
 }
@@ -316,7 +314,7 @@ proc::alloc(void)
  p = new proc(xnspid->allockey());
  if (p == nullptr)
-    return nullptr;
+    throw_bad_alloc();
  p->cpuid = mycpu()->id;
  initprocgc(p);
@@ -456,7 +454,7 @@ fork(int flags)
  // Allocate process.
  if((np = proc::alloc()) == 0)
-    throw_bad_alloc();
+    return -1;
  auto proc_cleanup = scoped_cleanup([&np]() {
    if (!xnspid->remove(np->pid, &np))
@@ -522,6 +520,9 @@ finishproc(struct proc *p, bool removepid)
    p->pgmap->dec();
  if (p->uwq != nullptr)
    p->uwq->dec();
+  if (p->kstack)
+    ksfree(slab_stack, p->kstack);
  p->pid = 0;
  p->parent = 0;
  p->name[0] = 0;
@@ -561,8 +562,10 @@ wait(void)
          w->rip = (void*) finishproc;
          w->arg0 = p;
          w->arg1 = 0;
-          assert(wqcrit_push(w, p->run_cpuid_) >= 0);
+          if (wqcrit_push(w, p->run_cpuid_) < 0) {
+            delete w;
+            finishproc(p, 0);
+          }
 	  return pid;
 	}
 	release(&p->lock);