Re: [PATCH v4 12/12] sched,signal,ptrace: Rework TASK_TRACED, TASK_STOPPED state

Steven Rostedt
2022-06-28T22:48:50Z

On Tue, 28 Jun 2022 17:42:22 -0500
"Eric W. Biederman" <ebiederm@xmission.com> wrote:

> diff --git a/kernel/ptrace.c b/kernel/ptrace.c
> index 156a99283b11..cb85bcf84640 100644
> --- a/kernel/ptrace.c
> +++ b/kernel/ptrace.c
> @@ -202,6 +202,7 @@ static bool ptrace_freeze_traced(struct task_struct *task)
> spin_lock_irq(&task->sighand->siglock);
> if (task_is_traced(task) && !looks_like_a_spurious_pid(task) &&
> !__fatal_signal_pending(task)) {
> + smp_rmb();
> task->jobctl |= JOBCTL_PTRACE_FROZEN;
> ret = true;
> }
> diff --git a/kernel/signal.c b/kernel/signal.c
> index edb1dc9b00dc..bcd576e9de66 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -2233,6 +2233,7 @@ static int ptrace_stop(int exit_code, int why, unsigned long message,
> return exit_code;
>
> set_special_state(TASK_TRACED);
> + smp_wmb();
> current->jobctl |= JOBCTL_TRACED;
>

Are not these both done under the sighand->siglock spinlock?

That is, the two paths should already be synchronized, and the memory
barriers will not help anything inside the locks. The locking should (and
must) handle all that.

-- Steve