When adding folio_memcg function call in the zram module for
Android16-6.12, the following error occurs during compilation:
ERROR: modpost: "cgroup_mutex" [../soc-repo/zram.ko] undefined!

This error is caused by the indirect call to lockdep_is_held(&cgroup_mutex)
within folio_memcg. The export setting for cgroup_mutex is controlled by
the CONFIG_PROVE_RCU macro. If CONFIG_LOCKDEP is enabled while
CONFIG_PROVE_RCU is not, this compilation error will occur.

To resolve this issue, add a parallel macro CONFIG_LOCKDEP control to
ensure cgroup_mutex is properly exported when needed.

Signed-off-by: gao xu <gaoxu2@honor.com>
---
 kernel/cgroup/cgroup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 447ac857e..9e60ff629 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -90,7 +90,7 @@
 DEFINE_MUTEX(cgroup_mutex);
 DEFINE_SPINLOCK(css_set_lock);
 
-#ifdef CONFIG_PROVE_RCU
+#if (defined CONFIG_PROVE_RCU || defined CONFIG_LOCKDEP)
 EXPORT_SYMBOL_GPL(cgroup_mutex);
 EXPORT_SYMBOL_GPL(css_set_lock);
 #endif
-- 
2.17.1

On Thu, Apr 17, 2025 at 07:30:00AM +0000, gaoxu wrote:
> When adding folio_memcg function call in the zram module for
> Android16-6.12, the following error occurs during compilation:
> ERROR: modpost: "cgroup_mutex" [../soc-repo/zram.ko] undefined!
> 
> This error is caused by the indirect call to lockdep_is_held(&cgroup_mutex)
> within folio_memcg. The export setting for cgroup_mutex is controlled by
> the CONFIG_PROVE_RCU macro. If CONFIG_LOCKDEP is enabled while
> CONFIG_PROVE_RCU is not, this compilation error will occur.
> 
> To resolve this issue, add a parallel macro CONFIG_LOCKDEP control to
> ensure cgroup_mutex is properly exported when needed.
> 
> Signed-off-by: gao xu <gaoxu2@honor.com>

Applied to cgroup/for-6.15-fixes.

Thanks.

-- 
tejun

On 4/17/25 1:00 PM, gaoxu wrote:
[...]

> diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
> index 447ac857e..9e60ff629 100644
> --- a/kernel/cgroup/cgroup.c
> +++ b/kernel/cgroup/cgroup.c
> @@ -90,7 +90,7 @@
>  DEFINE_MUTEX(cgroup_mutex);
>  DEFINE_SPINLOCK(css_set_lock);
>  
> -#ifdef CONFIG_PROVE_RCU
> +#if (defined CONFIG_PROVE_RCU || defined CONFIG_LOCKDEP)
>  EXPORT_SYMBOL_GPL(cgroup_mutex);
>  EXPORT_SYMBOL_GPL(css_set_lock);
>  #endif


It can be triggered when CONFIG_LOCK_STAT=y is enabled, which
selects CONFIG_LOCKDEP=y and sets CONFIG_PROVE_RCU=n. The patch
looks good to me.

You may also want to update the description above DEFINE_MUTEX(cgroup_mutex);
to reflect the modifications introduced by this patch.

-- 
Cheers,
Kamalesh

> 
> On 4/17/25 1:00 PM, gaoxu wrote:
> [...]
> 
> > diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index
> > 447ac857e..9e60ff629 100644
> > --- a/kernel/cgroup/cgroup.c
> > +++ b/kernel/cgroup/cgroup.c
> > @@ -90,7 +90,7 @@
> >  DEFINE_MUTEX(cgroup_mutex);
> >  DEFINE_SPINLOCK(css_set_lock);
> >
> > -#ifdef CONFIG_PROVE_RCU
> > +#if (defined CONFIG_PROVE_RCU || defined CONFIG_LOCKDEP)
> >  EXPORT_SYMBOL_GPL(cgroup_mutex);
> >  EXPORT_SYMBOL_GPL(css_set_lock);
> >  #endif
> 
> 
> It can be triggered when CONFIG_LOCK_STAT=y is enabled, which selects
> CONFIG_LOCKDEP=y and sets CONFIG_PROVE_RCU=n. The patch looks good to
> me.
> 
> You may also want to update the description above
> DEFINE_MUTEX(cgroup_mutex); to reflect the modifications introduced by this
> patch.
Received, thanks!
> 
> --
> Cheers,
> Kamalesh

Thanks, Gao.

On Thu, Apr 17, 2025 at 07:30:00AM +0000, gaoxu <gaoxu2@honor.com> wrote:
> --- a/kernel/cgroup/cgroup.c
> +++ b/kernel/cgroup/cgroup.c
> @@ -90,7 +90,7 @@
>  DEFINE_MUTEX(cgroup_mutex);
>  DEFINE_SPINLOCK(css_set_lock);
>  
> -#ifdef CONFIG_PROVE_RCU
> +#if (defined CONFIG_PROVE_RCU || defined CONFIG_LOCKDEP)
  #if defined(CONFIG_PROVE_RCU) || defined(CONFIG_LOCKDEP)

seems more conventional wrt existing code.
But in principle

Acked-by: Michal Koutný <mkoutny@suse.com>