Ananth N Mavinakayanahalli wrote:
>
> --- utrace-6mar.orig/kernel/utrace.c
> +++ utrace-6mar/kernel/utrace.c
> @@ -123,12 +123,15 @@ static inline bool exclude_utrace(struct
> */
> static inline int utrace_attach_delay(struct task_struct *target)
> {
> - if ((target->flags & PF_STARTING) && target->real_parent != current)
> - do {
> - schedule_timeout_interruptible(1);
> - if (signal_pending(current))
> - return -ERESTARTNOINTR;
> - } while (target->flags & PF_STARTING);
> + if ((target->flags & PF_STARTING) && target->real_parent != current) {
> + if (target->real_parent != current->real_parent) {
But target->real_parent == current->real_parent doesn't mean current
is a creator? It is possible that current's ->real_parent does fork().
And even with CLONE_THREAD, this doesn't mean we are creator, but the
commment says "The creator gets the first chance to attach".
Perhaps we can intruduce the new UTRACE_ATTACH_XXX, this flags should
be used when utrace_attach_task() is called from ->report_clone(), and
then something like
--- kernel/utrace.c
+++ kernel/utrace.c
@@ -130,12 +130,11 @@ static inline bool exclude_utrace(struct
*/
static inline int utrace_attach_delay(struct task_struct *target)
{
- if ((target->flags & PF_STARTING) && target->real_parent !=
current)
- do {
- schedule_timeout_interruptible(1);
- if (signal_pending(current))
- return -ERESTARTNOINTR;
- } while (target->flags & PF_STARTING);
+ while (unlikely(target->flags & PF_STARTING)) {
+ schedule_timeout_interruptible(1);
+ if (signal_pending(current))
+ return -ERESTARTNOINTR;
+ }
return 0;
}
@@ -267,7 +266,8 @@ struct utrace_engine *utrace_attach_task
engine->ops = ops;
engine->data = data;
- ret = utrace_attach_delay(target);
+ if (!(flags & UTRACE_ATTACH_XXX))
+ ret = utrace_attach_delay(target);
if (likely(!ret))
ret = utrace_add_engine(target, utrace, engine,
flags, ops, data);
when ->report_clone() is called current == creator always.
Yes, this is ugly, I agree.
We can also add "struct task_struct *creator" to "struct utrace". It is
be set by tracehook_finish_clone/utrace_init_task, and it is cleared by
tracehook_report_clone() path. In that case we do not need PF_STARTING.
But this blows task_struct...
Oleg.
