[patch 01/38] percpu: Sanitize __percpu_qual include hell

Thomas Gleixner
2026-04-10T12:18:39Z

Slapping __percpu_qual into the next available header is sloppy at best.

It's required by __percpu which is defined in compiler_types.h and that is
meant to be included without requiring a boatload of other headers so that
a struct or function declaration can contain a __percpu qualifier w/o
further prerequisites.

This implicit dependency on linux/percpu.h makes that impossible and causes
a major problem when trying to seperate headers.

Create asm/percpu_types.h and move it there. Include that from
compiler_types.h and the whole recursion problem goes away.

Signed-off-by: Thomas Gleixner <tglx@kernel.org
Cc: Arnd Bergmann <arnd@arndb.de>
---
arch/x86/include/asm/percpu.h | 5 -----
arch/x86/include/asm/percpu_types.h | 17 +++++++++++++++++
include/asm-generic/Kbuild | 1 +
include/asm-generic/percpu_types.h | 20 ++++++++++++++++++++
include/linux/compiler_types.h | 1 +
5 files changed, 39 insertions(+), 5 deletions(-)

--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -40,12 +40,10 @@
#endif

#define __percpu_prefix
-#define __percpu_seg_override CONCATENATE(__seg_, __percpu_seg)

#else /* !CONFIG_CC_HAS_NAMED_AS: */

#define __percpu_prefix __force_percpu_prefix
-#define __percpu_seg_override

#endif /* CONFIG_CC_HAS_NAMED_AS */

@@ -82,7 +80,6 @@

#define __force_percpu_prefix
#define __percpu_prefix
-#define __percpu_seg_override

#define PER_CPU_VAR(var) (var)__percpu_rel

@@ -92,8 +89,6 @@
# define __my_cpu_type(var) typeof(var)
# define __my_cpu_ptr(ptr) (ptr)
# define __my_cpu_var(var) (var)
-
-# define __percpu_qual __percpu_seg_override
#else
# define __my_cpu_type(var) typeof(var) __percpu_seg_override
# define __my_cpu_ptr(ptr) (__my_cpu_type(*(ptr))*)(__force uintptr_t)(ptr)
--- /dev/null
+++ b/arch/x86/include/asm/percpu_types.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_PERCPU_TYPES_H
+#define _ASM_X86_PERCPU_TYPES_H
+
+#if defined(CONFIG_SMP) && defined(CONFIG_CC_HAS_NAMED_AS)
+#define __percpu_seg_override CONCATENATE(__seg_, __percpu_seg)
+#else /* !CONFIG_CC_HAS_NAMED_AS: */
+#define __percpu_seg_override
+#endif
+
+#if defined(CONFIG_USE_X86_SEG_SUPPORT) && defined(USE_TYPEOF_UNQUAL)
+#define __percpu_qual __percpu_seg_override
+#endif
+
+#include <asm-generic/percpu_types.h>
+
+#endif
--- a/include/asm-generic/Kbuild
+++ b/include/asm-generic/Kbuild
@@ -44,6 +44,7 @@ mandatory-y += module.lds.h
mandatory-y += msi.h
mandatory-y += pci.h
mandatory-y += percpu.h
+mandatory-y += percpu_types.h
mandatory-y += pgalloc.h
mandatory-y += preempt.h
mandatory-y += rqspinlock.h
--- /dev/null
+++ b/include/asm-generic/percpu_types.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_GENERIC_PERCPU_TYPES_H_
+#define _ASM_GENERIC_PERCPU_TYPES_H_
+
+#ifndef __ASSEMBLER__
+/*
+ * __percpu_qual is the qualifier for the percpu named address space.
+ *
+ * Most arches use generic named address space for percpu variables but
+ * some arches define percpu variables in different named address space
+ * (on the x86 arch, percpu variable may be declared as being relative
+ * to the %fs or %gs segments using __seg_fs or __seg_gs named address
+ * space qualifier).
+ */
+#ifndef __percpu_qual
+# define __percpu_qual
+#endif
+
+#endif /* __ASSEMBLER__ */
+#endif /* _ASM_GENERIC_PERCPU_TYPES_H_ */
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -41,6 +41,7 @@
# define BTF_TYPE_TAG(value) /* nothing */
#endif

+#include <asm/percpu_types.h>
#include <linux/compiler-context-analysis.h>

/* sparse defines __CHECKER__; see Documentation/dev-tools/sparse.rst */