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authorDennis Zhou <dennis@kernel.org>2021-02-14 17:16:33 +0000
committerDennis Zhou <dennis@kernel.org>2021-02-14 18:15:15 +0000
commit258e0815e2b1706e87c0d874211097aa8a7aa52f (patch)
treeb98cacd48ddbbdfb81a243053bfd1fbf27d9a5fb
parentd7d29ac76f7efb506bcecc092641e704f791d92d (diff)
percpu: fix clang modpost section mismatch
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/202012220454.9F6Bkz9q-lkp@intel.com/ [2] https://lore.kernel.org/lkml/CAK8P3a2ZWfNeXKSm8K_SUhhwkor17jFo3xApLXjzfPqX0eUDUA@mail.gmail.com/ Reported-by: kernel test robot <lkp@intel.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Dennis Zhou <dennis@kernel.org>
-rw-r--r--include/linux/compiler_attributes.h6
-rw-r--r--mm/percpu.c2
2 files changed, 7 insertions, 1 deletions
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
@@ -211,6 +211,12 @@
#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.
*
* gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
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)