Re: [PATCH] drm/vblank: Restart enabling vblank timer on possible deadlock

[Thomas Zimmermann <tzimmermann@suse.de>]

Hi

Am 02.11.26 um 18:15 schrieb Ville Syrjälä:
[...]
> But what I'm thinking is:

I've ran a lengthy session to explore various solutions.

> - stop with the explicit cancel entirely and just rely on the
>    timer cancelling itself
> - try to start the timer in vblank_enable(), and if that can somehow
>    fail because the timer is still running it should be fine because
>    the self cancellation should anyway have been aborted

Having an old vblank timer still running while enable_vblank sets up a 
new one can mess up the hrtimer's internal ordering. It's full of subtle 
bugs, according to my LLM.


> - explicitly wait for the timer to have stoppped in drm_vblank_off()
>    to make sure the wrong interval can't leak from one mode to
>    another

I'll soon send out a series implementing this idea.

Best regards
Thomas

>

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Stefan Gaiser, Jochen Jaser, Abhinav Puri, (HRB 36809, AG Nürnberg)