linuxkpi: Factorize duplicated code in `linux_wait_event_common()` and `linux_schedule_timeout()`

[dumbbell]

Summary

There are two other functions calling linux_add_to_sleepqueue(), but the logic is slightly different. Factorizing them would make the code any cleaner.

This is part of the update of DRM drivers to Linux 6.7. This is a follow-up to D48755.

Sponsored by: The FreeBSD Foundation

[markj]

sys/compat/linuxkpi/common/src/linux_schedule.c

310

We can just pass 0 instead of the state here. linux_add_to_sleepqueue() only cares about whether the sleep is interruptible or not, i.e., the value is only 0 or TASK_INTERRUPTIBLE. I don't think that flag is ever set in task->state.

[dumbbell]

sys/compat/linuxkpi/common/src/linux_schedule.c

310

I think it is set. Here are two examples from the i915 driver:

• From https://github.com/dumbbell/drm-kmod/blob/update-to-linux-6.8/drivers/gpu/drm/i915/i915_hwmon.c#L409-L421:

prepare_to_wait(&ddat->waitq, &wait, TASK_INTERRUPTIBLE);
// ...
schedule();

• From https://github.com/dumbbell/drm-kmod/blob/update-to-linux-6.8/drivers/gpu/drm/i915/display/intel_crtc.c#L597-L614:

prepare_to_wait(wq, &wait, TASK_UNINTERRUPTIBLE);
// ...
timeout = schedule_timeout(timeout);

prepare_to_wait() calls set_task_state() which sets task->state:
https://github.com/dumbbell/freebsd-src/blob/drm-related-linuxkpi-changes/sys/compat/linuxkpi/common/src/linux_schedule.c#L267

then both schedule() and schedule_timeout() call linux_schedule_timeout().

[markj]

sys/compat/linuxkpi/common/src/linux_schedule.c

310

Thank you, I didn't realize it worked that way.

[dumbbell]

I abandon this revision; see the discussion in D48755.