X-Git-Url: http://git.samba.org/samba.git/?a=blobdiff_plain;f=kernel%2Fptrace.c;h=f34d798ef4a25831b98090a7b85fa6d3b93d0de2;hb=f46a6804135795f77d096ab0128f27531c7d051c;hp=74a3d693c196810f9eed784a2825ea50a7f9db83;hpb=bb9c03d8a6893517737b16fdbeb54be3c73b3023;p=sfrench%2Fcifs-2.6.git

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 74a3d693c196..f34d798ef4a2 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -324,26 +324,32 @@ int ptrace_detach(struct task_struct *child, unsigned int data)
 }
 
 /*
- * Detach all tasks we were using ptrace on.
+ * Detach all tasks we were using ptrace on. Called with tasklist held
+ * for writing, and returns with it held too. But note it can release
+ * and reacquire the lock.
  */
 void exit_ptrace(struct task_struct *tracer)
 {
 	struct task_struct *p, *n;
 	LIST_HEAD(ptrace_dead);
 
-	write_lock_irq(&tasklist_lock);
+	if (likely(list_empty(&tracer->ptraced)))
+		return;
+
 	list_for_each_entry_safe(p, n, &tracer->ptraced, ptrace_entry) {
 		if (__ptrace_detach(tracer, p))
 			list_add(&p->ptrace_entry, &ptrace_dead);
 	}
-	write_unlock_irq(&tasklist_lock);
 
+	write_unlock_irq(&tasklist_lock);
 	BUG_ON(!list_empty(&tracer->ptraced));
 
 	list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_entry) {
 		list_del_init(&p->ptrace_entry);
 		release_task(p);
 	}
+
+	write_lock_irq(&tasklist_lock);
 }
 
 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)