Re: [PATCH] sched_ext: Fix print_scx_info() build error on !CONFIG_EXT_SUB_SCHED kernels

[Andrea Righi <arighi@nvidia.com>]

On Sat, Mar 28, 2026 at 02:21:42AM +0800, Cheng-Yang Chou wrote:
> Hi Tejun,
> 
> On Fri, Mar 27, 2026 at 07:18:59AM -1000, Tejun Heo wrote:
> > On Fri, Mar 27, 2026 at 01:35:53PM +0800, Cheng-Yang Chou wrote:
> > > Hi Tejun,
> > > 
> > > On Thu, Mar 26, 2026 at 04:09:15PM +0800, Cheng-Yang Chou wrote:
> > > > scx_task_sched_rcu() is only available when CONFIG_EXT_SUB_SCHED is
> > > > enabled. Wrap the call with #ifdef CONFIG_EXT_SUB_SCHED and fall back
> > > > to rcu_dereference(scx_root) for the non-sub-sched case, which is
> > > > semantically equivalent.
> > > > 
> > > > Fixes: 60d4b17e886a ("sched_ext: Choose the right sch->ops.name to output in the print_scx_info()")
> > > > Reported-by: kernel test robot <lkp@intel.com>
> > > > Closes: https://lore.kernel.org/oe-kbuild-all/202603261453.8kiJImYo-lkp@intel.com/
> > > > Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
> > 
> > Have you tried reproducing the problem? This is trivial to try to reproduce.
> > You aren't even doing the absoulte minimum. Before sending patches, read the
> > relevant code and reproduce the problem. I get that AI makes it easy to pump
> > up the volume but try to reduce the volume and improve the actual
> > contribution. Otherwise, I'll have to mostly ignore your emails.
> 
> Actually, I can reproduce this error on my end with the provided config.
> This patch does fix the issue.
> 
> I'll make sure to include the test log in my future submissions to
> avoid any confusion.
> 
> Here is the full log for this reproduction:

For what I see It should be fixed already in Tejun's branch:
git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext.git

From kernel/sched/ext_internal.h:

#ifdef CONFIG_EXT_SUB_SCHED
...
static inline struct scx_sched *scx_task_sched_rcu(const struct task_struct *p)
{
        return rcu_dereference_all(p->scx.sched);
}
...
#else   /* CONFIG_EXT_SUB_SCHED */
static inline struct scx_sched *scx_task_sched_rcu(const struct task_struct *p)
{
        return rcu_dereference_all(scx_root);
}
...

Try with the for-7.1 branch.

-Andrea