linux-kernel - [PATCH v2 1/2] sched.h: always_inline alloc_tag

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Message-ID: <20240704132506.1011978-1-surenb@google.com>
Date: Thu,  4 Jul 2024 06:25:05 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: akpm@...ux-foundation.org
Cc: mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com, 
	vincent.guittot@...aro.org, chris@...kel.net, jcmvbkbc@...il.com, 
	kent.overstreet@...ux.dev, linux-kernel@...r.kernel.org, lkp@...el.com, 
	surenb@...gle.com, stable@...r.kernel.org
Subject: [PATCH v2 1/2] sched.h: always_inline alloc_tag_{save|restore} to fix
 modpost warnings

Mark alloc_tag_{save|restore} as always_inline to fix the following
modpost warnings:

WARNING: modpost: vmlinux: section mismatch in reference: alloc_tag_save+0x1c (section: .text.unlikely) -> initcall_level_names (section: .init.data)
WARNING: modpost: vmlinux: section mismatch in reference: alloc_tag_restore+0x3c (section: .text.unlikely) -> initcall_level_names (section: .init.data)

The warnings happen when these functions are called from an __init
function and they don't get inlined (remain in the .text section) while
the value returned by get_current() points into .init.data section.
Assuming get_current() always returns a valid address, this situation can
happen only during init stage and accessing .init.data from .text section
during that stage should pose no issues.

Fixes: 22d407b164ff ("lib: add allocation tagging support for memory allocation profiling")
Reported-by: kernel test robot <lkp@...el.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202407032306.gi9nZsBi-lkp@intel.com/
Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
Cc: Kent Overstreet <kent.overstreet@...ux.dev>
Cc: <stable@...r.kernel.org>
---

Changes since v1 [1]:
- Added the second patch to resolve follow-up warnings
- Expanded changelog description, per Andrew Morton
- CC'ed stable, per Andrew Morton
- Added Fixes tag, per Andrew Morton

[1] https://lore.kernel.org/all/20240703221520.4108464-1-surenb@google.com/

 include/linux/sched.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 61591ac6eab6..a5f4b48fca18 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2192,13 +2192,13 @@ static inline int sched_core_idle_cpu(int cpu) { return idle_cpu(cpu); }
 extern void sched_set_stop_task(int cpu, struct task_struct *stop);
 
 #ifdef CONFIG_MEM_ALLOC_PROFILING
-static inline struct alloc_tag *alloc_tag_save(struct alloc_tag *tag)
+static __always_inline struct alloc_tag *alloc_tag_save(struct alloc_tag *tag)
 {
 	swap(current->alloc_tag, tag);
 	return tag;
 }
 
-static inline void alloc_tag_restore(struct alloc_tag *tag, struct alloc_tag *old)
+static __always_inline void alloc_tag_restore(struct alloc_tag *tag, struct alloc_tag *old)
 {
 #ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG
 	WARN(current->alloc_tag != tag, "current->alloc_tag was changed:\n");

base-commit: 795c58e4c7fc6163d8fb9f2baa86cfe898fa4b19
-- 
2.45.2.803.g4e1b14247a-goog