Re: [akpm-mm:mm-new] BUILD REGRESSION b4fc90c82982d98959af08b4320420bcfc01303b

[Andrew Morton <akpm@linux-foundation.org>]

On Sun, 27 Sep 2026 16:00:49 +0800 kernel test robot <lkp@intel.com> wrote:

> tree/branch: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-new
> branch HEAD: b4fc90c82982d98959af08b4320420bcfc01303b  mm/swap, PM: hibernate: atomically replace hibernation pin
> 
> Error/Warning (recently discovered and may have been fixed):
> 
>     https://lore.kernel.org/oe-kbuild-all/202609160337.WJiD9BqX-lkp@intel.com
>     https://lore.kernel.org/oe-kbuild-all/202609171159.oaB1OaSG-lkp@intel.com
>     https://lore.kernel.org/oe-kbuild-all/202609270030.Y0QVBPmK-lkp@intel.com
> 
>     aarch64-linux-ld: Unexpected GOT/PLT entries detected!
>     aarch64-linux-ld: Unexpected run-time procedure linkages detected!
>     arena.c:(.text+0x11fc): undefined reference to `__check_safe_pte_update'
>     fs/proc/task_mmu.c:3450:17: error: implicit declaration of function 'drop_rcu' [-Werror=implicit-function-declaration]
>     fs/proc/task_mmu.c:3450:3: error: call to undeclared function 'drop_rcu'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
>     fs/proc/task_mmu.c:3450:3: error: implicit declaration of function 'drop_rcu'; did you mean 'drop_slab'? [-Werror=implicit-function-declaration]
>     fs/proc/task_mmu.c:3452:17: error: implicit declaration of function 'reacquire_rcu' [-Werror=implicit-function-declaration]
>     fs/proc/task_mmu.c:3452:3: error: call to undeclared function 'reacquire_rcu'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
>     fs/proc/task_mmu.c:3452:3: error: implicit declaration of function 'reacquire_rcu'; did you mean 'get_file_rcu'? [-Werror=implicit-function-declaration]
>     gup.c:(.text+0x2b48): undefined reference to `__check_safe_pte_update'
>     hugetlbpage.c:(.text+0x1a8): undefined reference to `__check_safe_pte_update'
>     memory.c:(.text+0x3418): undefined reference to `__check_safe_pte_update'
>     mmu.c:(.text+0x9a8): undefined reference to `__check_safe_pte_update'

Thanks.  Against "proc/task_mmu: remove unnecessary inlines in function
definitions":


From: Andrew Morton <akpm@linux-foundation.org>
Subject: proc-task_mmu-remove-unnecessary-inlines-in-function-definitions-fix
Date: Sun Sep 27 10:59:53 AM PDT 2026

fix CONFIG_NUMA=y && CONFIG_PROC_PAGE_MONITOR=n build

show_numa_map() uses drop_rcu() and reacquire_rcu(), but those helpers are
currently built only when CONFIG_PROC_PAGE_MONITOR is enabled.  A kernel
with CONFIG_NUMA=y and CONFIG_PROC_PAGE_MONITOR=n therefore fails to build
with implicit declarations for both helpers.

Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/proc/task_mmu.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/proc/task_mmu.c~proc-task_mmu-remove-unnecessary-inlines-in-function-definitions-fix
+++ a/fs/proc/task_mmu.c
@@ -196,7 +196,7 @@ static bool fallback_to_mmap_lock(struct
 	return true;
 }
 
-#ifdef CONFIG_PROC_PAGE_MONITOR
+#if defined(CONFIG_PROC_PAGE_MONITOR) || defined(CONFIG_NUMA)
 static void drop_rcu(struct proc_maps_private *priv)
 {
 	if (priv->lock_ctx.mmap_locked)
_