Re: [PATCH 0/5] Fix SCHED_DEADLINE bandwidth accounting during suspend

[Juri Lelli <juri.lelli@redhat.com>]

Hi Jon,

On 04/03/25 15:32, Jon Hunter wrote:
> Hi Juri,
> 
> On 04/03/2025 08:40, Juri Lelli wrote:
> > Hello!
> > 
> > Jon reported [1] a suspend regression on a Tegra board configured to
> > boot with isolcpus and bisected it to commit 53916d5fd3c0
> > ("sched/deadline: Check bandwidth overflow earlier for hotplug").
> > 
> > Root cause analysis pointed out that we are currently failing to
> > correctly clear and restore bandwidth accounting on root domains after
> > changes that initiate from partition_sched_domains(), as it is the case
> > for suspend operations on that board.
> > 
> > The way we currently make sure that accounting properly follows root
> > domain changes is quite convoluted and was indeed missing some corner
> > cases. So, instead of adding yet more fragile operations, I thought we
> > could simplify things by always clearing and rebuilding bandwidth
> > information on all domains after an update is complete. Also, we should
> > be ignoring DEADLINE special tasks when doing so (e.g. sugov), since we
> > ignore them already for runtime enforcement and admission control
> > anyway.
> > 
> > The following implements the approach by:
> > 
> > - 01/05: filter out DEADLINE special tasks
> > - 02/05: preparatory wrappers to be able to grab sched_domains_mutex on
> >           UP
> > - 03/05: generalize unique visiting of root domains so that we can
> >           re-use the mechanism elsewhere
> > - 04/05: the bulk of the approach, clean and rebuild after changes
> > - 05/05: clean up a now redundant call
> > 
> > Please test and review. The set is also available at
> > 
> > git@github.com:jlelli/linux.git upstream/deadline/domains-suspend
> 
> 
> I know that this is still under review, but I have tested on my side and it
> is working for me, so feel free to include my ...
> 
> Tested-by: Jon Hunter <jonathanh@nvidia.com>

Great to hear this and thanks for the super quick turn around with
testing. I will be implementing the changes that Waiman (and possibly
others) is suggesting and post a new version soon.

Best,
Juri