pcpu_build_alloc_info() is an __init function that makes a call to
cpumask_clear_cpu(). With CONFIG_GCOV_PROFILE_ALL enabled, the inline
heuristics are modified and such cpumask_clear_cpu() which is marked
inline doesn't get inlined. Because it works on mask in __initdata,
modpost throws a section mismatch error.
Arnd sent a patch with the flatten attribute as an alternative [2]. I've
added it to compiler_attributes.h.
modpost complaint:
WARNING: modpost: vmlinux.o(.text+0x735425): Section mismatch in reference from the function cpumask_clear_cpu() to the variable .init.data:pcpu_build_alloc_info.mask
The function cpumask_clear_cpu() references
the variable __initdata pcpu_build_alloc_info.mask.
This is often because cpumask_clear_cpu lacks a __initdata
annotation or the annotation of pcpu_build_alloc_info.mask is wrong.
clang output:
mm/percpu.c:2724:5: remark: cpumask_clear_cpu not inlined into pcpu_build_alloc_info because too costly to inline (cost=725, threshold=325) [-Rpass-missed=inline]
[1] https://lore.kernel.org/linux-mm/[email protected]/
[2] https://lore.kernel.org/lkml/CAK8P3a2ZWfNeXKSm8K_SUhhwkor17jFo3xApLXjzfPqX0eUDUA@mail.gmail.com/
Reported-by: kernel test robot <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Nick Desaulniers <[email protected]>
Signed-off-by: Dennis Zhou <[email protected]>
---
include/linux/compiler_attributes.h | 6 ++++++
mm/percpu.c | 2 +-
2 files changed, 7 insertions(+), 1 deletion(-)
diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h
index ea5e04e75845..c043b8d2b17b 100644
--- a/include/linux/compiler_attributes.h
+++ b/include/linux/compiler_attributes.h
@@ -210,6 +210,12 @@
# define fallthrough do {} while (0) /* fallthrough */
#endif
+/*
+ * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes
+ * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten
+ */
+# define __flatten __attribute__((flatten))
+
/*
* Note the missing underscores.
*
diff --git a/mm/percpu.c b/mm/percpu.c
index 80f8f885a990..6596a0a4286e 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -2663,7 +2663,7 @@ early_param("percpu_alloc", percpu_alloc_setup);
* On success, pointer to the new allocation_info is returned. On
* failure, ERR_PTR value is returned.
*/
-static struct pcpu_alloc_info * __init pcpu_build_alloc_info(
+static struct pcpu_alloc_info * __init __flatten pcpu_build_alloc_info(
size_t reserved_size, size_t dyn_size,
size_t atom_size,
pcpu_fc_cpu_distance_fn_t cpu_distance_fn)
--
2.30.0.478.g8a0d178c01-goog