Re: [PATCH 5.15 00/23] 5.15.160-rc1 review

[NeilBrown]

On Wed, 29 May 2024, Chuck Lever III wrote:
> 
> 
> > On May 28, 2024, at 6:01 PM, NeilBrown <neilb@xxxxxxx> wrote:
> > 
> > On Wed, 29 May 2024, Chuck Lever III wrote:
> >> 
> >> 
> >>> On May 28, 2024, at 10:18 AM, Jon Hunter <jonathanh@xxxxxxxxxx> wrote:
> >>> 
> >>> 
> >>> On 28/05/2024 14:14, Chuck Lever III wrote:
> >>>>> On May 28, 2024, at 5:04 AM, Jon Hunter <jonathanh@xxxxxxxxxx> wrote:
> >>>>> 
> >>>>> 
> >>>>> On 25/05/2024 15:20, Greg Kroah-Hartman wrote:
> >>>>>> On Sat, May 25, 2024 at 12:13:28AM +0100, Jon Hunter wrote:
> >>>>>>> Hi Greg,
> >>>>>>> 
> >>>>>>> On 23/05/2024 14:12, Greg Kroah-Hartman wrote:
> >>>>>>>> This is the start of the stable review cycle for the 5.15.160 release.
> >>>>>>>> There are 23 patches in this series, all will be posted as a response
> >>>>>>>> to this one.  If anyone has any issues with these being applied, please
> >>>>>>>> let me know.
> >>>>>>>> 
> >>>>>>>> Responses should be made by Sat, 25 May 2024 13:03:15 +0000.
> >>>>>>>> Anything received after that time might be too late.
> >>>>>>>> 
> >>>>>>>> The whole patch series can be found in one patch at:
> >>>>>>>> https://www.kernel.org/pub/linux/kernel/v5.x/stable-review/patch-515.160-rc1.gz
> >>>>>>>> or in the git tree and branch at:
> >>>>>>>> git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git linux-5.15.y
> >>>>>>>> and the diffstat can be found below.
> >>>>>>>> 
> >>>>>>>> thanks,
> >>>>>>>> 
> >>>>>>>> greg k-h
> >>>>>>>> 
> >>>>>>>> -------------
> >>>>>>>> Pseudo-Shortlog of commits:
> >>>>>>> 
> >>>>>>> ...
> >>>>>>> 
> >>>>>>>> NeilBrown <neilb@xxxxxxx>
> >>>>>>>>     nfsd: don't allow nfsd threads to be signalled.
> >>>>>>> 
> >>>>>>> 
> >>>>>>> I am seeing a suspend regression on a couple boards and bisect is pointing
> >>>>>>> to the above commit. Reverting this commit does fix the issue.
> >>>>>> Ugh, that fixes the report from others.  Can you cc: everyone on that
> >>>>>> and figure out what is going on, as this keeps going back and forth..
> >>>>> 
> >>>>> 
> >>>>> Adding Chuck, Neil and Chris from the bug report here [0].
> >>>>> 
> >>>>> With the above applied to v5.15.y, I am seeing suspend on 2 of our boards fail. These boards are using NFS and on entry to suspend I am now seeing ...
> >>>>> 
> >>>>> Freezing of tasks failed after 20.002 seconds (1 tasks refusing to
> >>>>> freeze, wq_busy=0):
> >>>>> 
> >>>>> The boards appear to hang at that point. So may be something else missing?
> >>>> Note that we don't have access to hardware like this, so
> >>>> we haven't tested that patch (even the upstream version)
> >>>> with suspend on that hardware.
> >>> 
> >>> 
> >>> No problem, I would not expect you to have this particular hardware :-)
> >>> 
> >>>> So, it could be something missing, or it could be that
> >>>> patch has a problem.
> >>>> It would help us to know if you observe the same issue
> >>>> with an upstream kernel, if that is possible.
> >>> 
> >>> 
> >>> I don't observe this with either mainline, -next or any other stable branch. So that would suggest that something else is missing from linux-5.15.y.
> >> 
> >> That helps. It would be very helpful to have a reproducer I can
> >> use to confirm we have a fix. I'm sure this will be a process
> >> that involves a non-trivial number of iterations.
> > 
> > Missing upstream patch is
> > 
> > Commit 9bd4161c5917 ("SUNRPC: change service idle list to be an llist")
> > 
> > This contains some freezer-related changes which probably should
> > have been a separate patch.
> 
> Thanks for tracking that down.
> 
> 
> > We probably just need to add "| TASK_FREEZABLE" in one or two places.
> > I'll post a patch for testing in a little while.
> 
> My understanding is that the stable maintainers prefer a backport
> of a patch (or patches) that are already applied to Linus' tree.

They also preferred a full backport of fs/nfsd/..  That hasn't gone so
well :-)

In this case we would need 

Commit f5d39b020809 ("freezer,sched: Rewrite core freezer logic")

to get TASK_FREEZABLE.
I doubt that would be a good choice.

NeilBrown


> 
> 
> --
> Chuck Lever
> 
> 
>