Re: Patch "Revert "cgroup_freezer: cgroup_freezing: Check if not frozen"" has been added to the 6.15-stable tree

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, Jul 29, 2025 at 09:22:10PM +0800, Chen Ridong wrote:
> 
> 
> On 2025/7/24 17:43, Greg KH wrote:
> > On Thu, Jul 24, 2025 at 05:38:52PM +0800, Chen Ridong wrote:
> >>
> >>
> >> On 2025/7/23 13:06, Greg KH wrote:
> >>> On Wed, Jul 23, 2025 at 09:01:43AM +0800, Chen Ridong wrote:
> >>>>
> >>>>
> >>>> On 2025/7/22 20:38, Greg KH wrote:
> >>>>> On Tue, Jul 22, 2025 at 08:25:49PM +0800, Chen Ridong wrote:
> >>>>>>
> >>>>>>
> >>>>>> On 2025/7/22 20:18, Greg KH wrote:
> >>>>>>> On Tue, Jul 22, 2025 at 09:29:13AM +0800, Chen Ridong wrote:
> >>>>>>>>
> >>>>>>>>> This is a note to let you know that I've just added the patch titled
> >>>>>>>>>
> >>>>>>>>>     Revert "cgroup_freezer: cgroup_freezing: Check if not frozen"
> >>>>>>>>>
> >>>>>>>>> to the 6.15-stable tree which can be found at:
> >>>>>>>>>     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> >>>>>>>>>
> >>>>>>>>> The filename of the patch is:
> >>>>>>>>>      revert-cgroup_freezer-cgroup_freezing-check-if-not-f.patch
> >>>>>>>>> and it can be found in the queue-6.15 subdirectory.
> >>>>>>>>>
> >>>>>>>>> If you, or anyone else, feels it should not be added to the stable tree, please let <stable@vger.kernel.org> know about it.
> >>>>>>>>>
> >>>>>>>>
> >>>>>>>> The patch ("sched,freezer: Remove unnecessary warning in __thaw_task") should also be merged to
> >>>>>>>> prevent triggering another warning in __thaw_task().
> >>>>>>>
> >>>>>>> What is the git commit id of that change in Linus's tree?
> >>>>>>>
> >>>>>>> thanks,
> >>>>>>>
> >>>>>>> greg k-h
> >>>>>>
> >>>>>> 9beb8c5e77dc10e3889ff5f967eeffba78617a88 ("sched,freezer: Remove unnecessary warning in __thaw_task")
> >>>>>
> >>>>> Thanks, but that didn't apply to 6.1.y or 6.6.y.  Shouldn't it also go
> >>>>> there as that's what this revert was applied back to.
> >>>>>
> >>>>> greg k-h
> >>>>
> >>>> Hi Greg,
> >>>>
> >>>> The commit 9beb8c5e77dc ("sched,freezer: Remove unnecessary warning...") should be merged together
> >>>> with 14a67b42cb6f ("Revert "cgroup_freezer: cgroup_freezing: Check if not frozen"") to avoid the
> >>>> warning for 6.1.y or 6.6.y.
> >>>
> >>> Ok, but 9beb8c5e77dc does not apply properly there.  Can you please
> >>> provide a working backport?
> >>>
> >>> thanks,
> >>>
> >>> greg k-h
> >>
> >> IIUC, we need to backport these two commits together:
> >> 1.commit 23ab79e8e469 ("freezer,sched: Do not restore saved_state of a thawed task")
> >> 2.commit 9beb8c5e77dc ("sched,freezer: Remove unnecessary warning...").
> >>
> >> After applying these prerequisites, the required change becomes minimal:
> >>
> >> diff --git a/kernel/freezer.c b/kernel/freezer.c
> >> index 4fad0e6fca64..288d1cce1fc4 100644
> >> --- a/kernel/freezer.c
> >> +++ b/kernel/freezer.c
> >> @@ -196,7 +196,7 @@ void __thaw_task(struct task_struct *p)
> >>         unsigned long flags, flags2;
> >>
> >>         spin_lock_irqsave(&freezer_lock, flags);
> >> -       if (WARN_ON_ONCE(freezing(p)))
> >> +       if (!frozen(p))
> >>                 goto unlock;
> >>
> >>         if (lock_task_sighand(p, &flags2)) {
> >>
> >> Would you like me to prepare and submit this patch for the stable branches (6.6.y and 6.1.y)?
> > 
> > Yes, please send me the missing patches as a series for each branch that
> > needs them.
> > 
> > thanks,
> > 
> > greg k-h
> 
> Hi Greg and maintainers,
> 
> I've sent the patch series for 6.6.y. Backporting commit 9beb8c5e77dc ("sched,freezer: Remove
> unnecessary warning...") requires 4 patches for 6.6.y, and the backport to 6.1.y would be even more
> complex.
> 
> As an alternative, I'm considering addressing the warning directly with the patch I mentioned
> previously. What are your thoughts on this approach?
> 
> The new patch:
> 
> diff --git a/kernel/freezer.c b/kernel/freezer.c
> index 4fad0e6fca64..288d1cce1fc4 100644
> --- a/kernel/freezer.c
> +++ b/kernel/freezer.c
> @@ -196,7 +196,7 @@ void __thaw_task(struct task_struct *p)
>         unsigned long flags, flags2;
> 
>         spin_lock_irqsave(&freezer_lock, flags);
> -       if (WARN_ON_ONCE(freezing(p)))
> +       if (!frozen(p))
>                 goto unlock;
> 
>         if (lock_task_sighand(p, &flags2)) {
> 

I have no idea, sorry, please work with the developers/maintainers of
the original change and get their approval.  But normally, we do NOT
want one-off changes being made to older kernel trees unless it has to
be done, as that makes maintaining them much much much harder over time.

thanks,

greg k-h