[tip: locking/core] percpu: Sanitize __percpu_qual include hell
From: tip-bot2 for Thomas Gleixner
Date: Wed Jun 03 2026 - 10:36:57 EST
The following commit has been merged into the locking/core branch of tip:
Commit-ID: c06cd66387da92e6cdac44e16c7b5ef9219c53ac
Gitweb: https://git.kernel.org/tip/c06cd66387da92e6cdac44e16c7b5ef9219c53ac
Author: Thomas Gleixner <tglx@xxxxxxxxxx>
AuthorDate: Tue, 02 Jun 2026 11:09:21 +02:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Wed, 03 Jun 2026 11:38:48 +02:00
percpu: Sanitize __percpu_qual include hell
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 separate headers.
Create asm/percpu_types.h and move it there. Include that from
compiler_types.h and the whole recursion problem goes away.
Fix up UM so it uses the generic header and includes it in the UM_HOST
build, which pulls in compiler_types.h. The USER_CFLAGS fix was suggested
by Richard.
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://patch.msgid.link/20260602090535.254874125@xxxxxxxxxx
---
arch/um/Makefile | 3 ++-
arch/um/include/asm/Kbuild | 1 +
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 | 19 +++++++++++++++++++
include/linux/compiler_types.h | 3 +++
include/linux/percpu.h | 9 +++++----
8 files changed, 48 insertions(+), 10 deletions(-)
create mode 100644 arch/x86/include/asm/percpu_types.h
create mode 100644 include/asm-generic/percpu_types.h
diff --git a/arch/um/Makefile b/arch/um/Makefile
index 721b652..937639e 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -71,7 +71,8 @@ USER_CFLAGS = $(patsubst $(KERNEL_DEFINES),,$(patsubst -I%,,$(KBUILD_CFLAGS))) \
-D_FILE_OFFSET_BITS=64 -idirafter $(srctree)/include \
-idirafter $(objtree)/include -D__KERNEL__ -D__UM_HOST__ \
-include $(srctree)/include/linux/compiler-version.h \
- -include $(srctree)/include/linux/kconfig.h
+ -include $(srctree)/include/linux/kconfig.h \
+ -idirafter $(ARCH_DIR)/include/generated
#This will adjust *FLAGS accordingly to the platform.
include $(srctree)/$(ARCH_DIR)/Makefile-os-Linux
diff --git a/arch/um/include/asm/Kbuild b/arch/um/include/asm/Kbuild
index 1b9b82b..e91ba12 100644
--- a/arch/um/include/asm/Kbuild
+++ b/arch/um/include/asm/Kbuild
@@ -16,6 +16,7 @@ generic-y += module.h
generic-y += module.lds.h
generic-y += parport.h
generic-y += percpu.h
+generic-y += percpu_types.h
generic-y += preempt.h
generic-y += runtime-const.h
generic-y += softirq_stack.h
diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index 4099814..cef9a4c 100644
--- 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)
diff --git a/arch/x86/include/asm/percpu_types.h b/arch/x86/include/asm/percpu_types.h
new file mode 100644
index 0000000..0aa3e47
--- /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
diff --git a/include/asm-generic/Kbuild b/include/asm-generic/Kbuild
index 2c53a1e..15df9dc 100644
--- 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
diff --git a/include/asm-generic/percpu_types.h b/include/asm-generic/percpu_types.h
new file mode 100644
index 0000000..a095cea
--- /dev/null
+++ b/include/asm-generic/percpu_types.h
@@ -0,0 +1,19 @@
+/* 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 architectures use generic named address space for percpu variables but
+ * some architectures define percpu variables in different named address space.
+ * E.g. on x86, 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_ */
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index e8fd775..7ad37ad 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -634,6 +634,9 @@ struct ftrace_likely_data {
#else
#define __unqual_scalar_typeof(x) __typeof_unqual__(x)
#endif
+
+#include <asm/percpu_types.h>
+
#endif /* !__ASSEMBLY__ */
/*
diff --git a/include/linux/percpu.h b/include/linux/percpu.h
index 85bf8dd..2f5a889 100644
--- a/include/linux/percpu.h
+++ b/include/linux/percpu.h
@@ -3,13 +3,14 @@
#define __LINUX_PERCPU_H
#include <linux/alloc_tag.h>
+#include <linux/cleanup.h>
+#include <linux/compiler_types.h>
+#include <linux/init.h>
#include <linux/mmdebug.h>
-#include <linux/preempt.h>
-#include <linux/smp.h>
#include <linux/pfn.h>
-#include <linux/init.h>
-#include <linux/cleanup.h>
+#include <linux/preempt.h>
#include <linux/sched.h>
+#include <linux/smp.h>
#include <asm/percpu.h>