Ah, and you forgot to CC lkml ;) let me resend my email.
Hi Jim,
Please do not use the attachments, just send the patch as plain text.
See Documentation/process/submitting-patches.rst
On 03/08, Jim Newsome wrote:
>
> --- a/kernel/exit.c
> +++ b/kernel/exit.c
> @@ -1462,8 +1462,61 @@ static long do_wait(struct wait_opts *wo)
> goto notask;
>
> set_current_state(TASK_INTERRUPTIBLE);
> +
> read_lock(&tasklist_lock);
> tsk = current;
> +
> + if (wo->wo_type == PIDTYPE_PID) {
> + // Optimization for PIDTYPE_PID. No need to iterate through
> child and
> + // tracee lists to find the target task.
I'd suggest to put this PIDTYPE_PID code into the new function.
> +
> + struct task_struct *real_parent = NULL;
> + struct task_struct *target = NULL;
> + bool do_regular_wait, do_ptrace_wait;
> +
> + // XXX: Do we need this? Or is the tasklist_lock sufficient?
> + rcu_read_lock();
No, you don't need rcu lock, tasklist_lock is sufficient
> + target = pid_task(wo->wo_pid, PIDTYPE_PID);
> + if (!target) {
> + rcu_read_unlock();
> + goto notask;
This is wrong, you forgot to drop tasklist_lock.
> + real_parent = !target->real_parent ? target->parent :
> + target->real_parent;
Hmm, I don't understand the line above... perhaps it connects to the
question below.
> + if (!real_parent) {
> + // XXX: Is it a kernel bug to get here? Or would this be
> + // true of the init process?
Afaics, parent/real_parent can't be NULL if pid_task() succeeds.
> + do_regular_wait = tsk == real_parent ||
> + (!(wo->wo_flags & __WNOTHREAD) &&
> + same_thread_group(tsk, real_parent));
> + do_ptrace_wait = target->ptrace &&
> + (tsk == target->parent ||
> + (!(wo->wo_flags & __WNOTHREAD) &&
> + same_thread_group(tsk, target->parent)));
> + rcu_read_unlock();
> +
> + if (do_regular_wait) {
> + retval =
> + wait_consider_task(wo, /* ptrace= */ 0, target);
> + if (retval) {
> + goto end;
> + }
> + }
> + if (do_ptrace_wait) {
> + retval =
> + wait_consider_task(wo, /* ptrace= */ 1, target);
> + if (retval) {
> + goto end;
> + }
> + }
> + read_unlock(&tasklist_lock);
> + goto notask;
This part looks correct at first glance...
Please redo and send V2 ;)
Oleg.
