linux-kernel - Re: [paulmck-rcu:dev.2025.09.15a 45/45] ERROR: modpost: "init_srcu_struct_fast" [kernel/rcu/rcutorture.ko] undefined!

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Message-ID: <0e09e4cb-058d-40fb-aa8d-9da68fb86a24@paulmck-laptop>
Date: Tue, 23 Sep 2025 06:01:52 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: kernel test robot <lkp@...el.com>
Cc: llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [paulmck-rcu:dev.2025.09.15a 45/45] ERROR: modpost:
 "init_srcu_struct_fast" [kernel/rcu/rcutorture.ko] undefined!

On Sat, Sep 20, 2025 at 03:10:55PM +0800, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev.2025.09.15a
> head:   f81c21ec3fca688bfcb6fa0abaf70404655765dc
> commit: f81c21ec3fca688bfcb6fa0abaf70404655765dc [45/45] rcutorture: Exercise DEFINE_STATIC_SRCU_FAST() and init_srcu_struct_fast()
> config: arm-randconfig-003-20250920 (https://download.01.org/0day-ci/archive/20250920/202509201519.udl3bu3X-lkp@intel.com/config)
> compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project 7c861bcedf61607b6c087380ac711eb7ff918ca6)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250920/202509201519.udl3bu3X-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@...el.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202509201519.udl3bu3X-lkp@intel.com/
> 
> All errors (new ones prefixed by >>, old ones prefixed by <<):
> 
> >> ERROR: modpost: "init_srcu_struct_fast" [kernel/rcu/rcutorture.ko] undefined!

I believe that this is fixed in current -rcu by the replacement commits
headed by the following commit:

bd3acc50cf8c ("rcutorture: Exercise DEFINE_STATIC_SRCU_FAST() and init_srcu_struct_fast()")

Please see below for the diff that should fix the commit in which
you found the failure.

And thank you for your testing efforts!!!

							Thanx, Paul

------------------------------------------------------------------------

diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index c81d5dfaf73753..26de47820c58cd 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -48,7 +48,9 @@ int __init_srcu_struct_fast(struct srcu_struct *ssp, const char *name, struct lo
 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
 int init_srcu_struct(struct srcu_struct *ssp);
+#ifndef CONFIG_TINY_SRCU
 int init_srcu_struct_fast(struct srcu_struct *ssp);
+#endif // #ifndef CONFIG_TINY_SRCU
 
 #define __SRCU_DEP_MAP_INIT(srcu_name)
 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h
index 4c2f2802393062..92e6ab53398fc0 100644
--- a/include/linux/srcutiny.h
+++ b/include/linux/srcutiny.h
@@ -45,9 +45,9 @@ void srcu_drive_gp(struct work_struct *wp);
  */
 #define DEFINE_SRCU(name) \
 	struct srcu_struct name = __SRCU_STRUCT_INIT(name, name, name, name)
-#define DEFINE_SRCU_FAST(name) DEFINE_SRCU(name)
 #define DEFINE_STATIC_SRCU(name) \
 	static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name, name, name)
+#define DEFINE_SRCU_FAST(name) DEFINE_SRCU(name)
 #define DEFINE_STATIC_SRCU_FAST(name) \
 	static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name, name, name)
 
@@ -55,6 +55,9 @@ void srcu_drive_gp(struct work_struct *wp);
 struct srcu_usage { };
 #define __SRCU_USAGE_INIT(name) { }
 #define __init_srcu_struct_fast __init_srcu_struct
+#ifndef CONFIG_DEBUG_LOCK_ALLOC
+#define init_srcu_struct_fast init_srcu_struct
+#endif // #ifndef CONFIG_DEBUG_LOCK_ALLOC
 
 void synchronize_srcu(struct srcu_struct *ssp);