On Tue, Sep 21, 2021 at 07:43:16PM +0200, Peter Zijlstra wrote:
> On Wed, Sep 15, 2021 at 04:18:01PM +0200, Vasily Gorbik wrote:
>
> > diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
> > index 291b857a6e20..2846a879f2dc 100644
> > --- a/kernel/livepatch/transition.c
> > +++ b/kernel/livepatch/transition.c
> > @@ -278,6 +278,8 @@ static int klp_check_stack(struct task_struct *task, char *err_buf)
> > * Try to safely switch a task to the target patch state. If it's currently
> > * running, or it's sleeping on a to-be-patched or to-be-unpatched function, or
> > * if the stack is unreliable, return false.
> > + *
> > + * Idle tasks are switched in the main loop when running.
> > */
> > static bool klp_try_switch_task(struct task_struct *task)
> > {
> > @@ -308,6 +310,12 @@ static bool klp_try_switch_task(struct task_struct *task)
> > rq = task_rq_lock(task, &flags);
> >
> > if (task_running(rq, task) && task != current) {
> > + /*
> > + * Idle task might stay running for a long time. Switch them
> > + * in the main loop.
> > + */
> > + if (is_idle_task(task))
> > + resched_curr(rq);
> > snprintf(err_buf, STACK_ERR_BUF_SIZE,
> > "%s: %s:%d is running\n", __func__, task->comm,
> > task->pid);
>
> So 'recently' we grew try_invoke_on_locked_down_task() (yes, that's a
> crap name), and I'm thinking this code is very similar to that. So
> perhaps we re-use that.
>
> Perhaps have func() > 0 imply resched.
>
> I'll have a play...
https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/log/?h=sched/livepatch
I'll write proper changelogs and post tomorrow,... (and fix robot fail,
if any).
(also, notes to later self:
- task_try_func() might need to re-check on_rq after acquiring rq_lock
- klp_send_signal() might want wake_up_process()/TASK_NORMAL due to TASK_IDLE
)
