Re: [PATCH v2] freezer,sched: Use saved_state to reduce some spurious wakeups

[Peter Zijlstra]

On Wed, Aug 30, 2023 at 10:42:39AM -0700, Elliot Berman wrote:

> Avoid the spurious wakeups by saving the state of TASK_FREEZABLE tasks.
> If the task was running before entering TASK_FROZEN state
> (__refrigerator()) or if the task received a wake up for the saved
> state, then the task is woken on thaw. saved_state from PREEMPT_RT locks
> can be re-used because freezer would not stomp on the rtlock wait flow:
> TASK_RTLOCK_WAIT isn't considered freezable.

You don't actually assert that anywhere I think, so the moment someone
makes that happen you crash and burn.

Also:

> -#ifdef CONFIG_PREEMPT_RT
> +#if IS_ENABLED(CONFIG_PREEMPT_RT) || IS_ENABLED(CONFIG_FREEZER)

That makes wakeup more horrible for everyone :/