Merge tag 'smp-core-2026-04-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull SMP core updates from Thomas Gleixner:

 - Switch smp_call_on_cpu() to user system_percpu_wq instead of
   system_wq a part of the ongoing workqueue restructuring

 - Improve the CSD-lock diagnostics for smp_call_function_single() to
   provide better debug mechanisms on weakly ordered systems.

 - Cache the current CPU number once in smp_call_function*() instead of
   retrieving it over and over.

 - Add missing kernel-doc comments all over the place

* tag 'smp-core-2026-04-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  smp: Use system_percpu_wq instead of system_wq
  smp: Improve smp_call_function_single() CSD-lock diagnostics
  smp: Get this_cpu once in smp_call_function
  smp: Add missing kernel-doc comments

1 files changed, 21 insertions, 17 deletions

diff --git a/include/linux/smp.h b/include/linux/smp.h
index 1ebd88026119..6925d15ccaa7 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -73,7 +73,7 @@ static inline void on_each_cpu(smp_call_func_t func, void *info, int wait)
 }
 
 /**
- * on_each_cpu_mask(): Run a function on processors specified by
+ * on_each_cpu_mask() - Run a function on processors specified by
  * cpumask, which may include the local processor.
  * @mask: The set of cpus to run on (only runs on online subset).
  * @func: The function to run. This must be fast and non-blocking.
@@ -239,13 +239,30 @@ static inline int get_boot_cpu_id(void)
 
 #endif /* !SMP */
 
-/**
+/*
  * raw_smp_processor_id() - get the current (unstable) CPU id
  *
- * For then you know what you are doing and need an unstable
+ * raw_smp_processor_id() is arch-specific/arch-defined and
+ * may be a macro or a static inline function.
+ *
+ * For when you know what you are doing and need an unstable
  * CPU id.
  */
 
+/*
+ * Allow the architecture to differentiate between a stable and unstable read.
+ * For example, x86 uses an IRQ-safe asm-volatile read for the unstable but a
+ * regular asm read for the stable.
+ */
+#ifndef __smp_processor_id
+#define __smp_processor_id() raw_smp_processor_id()
+#endif
+
+#ifdef CONFIG_DEBUG_PREEMPT
+  extern unsigned int debug_smp_processor_id(void);
+# define smp_processor_id() debug_smp_processor_id()
+
+#else
 /**
  * smp_processor_id() - get the current (stable) CPU id
  *
@@ -258,23 +275,10 @@ static inline int get_boot_cpu_id(void)
  *  - preemption is disabled;
  *  - the task is CPU affine.
  *
- * When CONFIG_DEBUG_PREEMPT; we verify these assumption and WARN
+ * When CONFIG_DEBUG_PREEMPT=y, we verify these assumptions and WARN
  * when smp_processor_id() is used when the CPU id is not stable.
  */
 
-/*
- * Allow the architecture to differentiate between a stable and unstable read.
- * For example, x86 uses an IRQ-safe asm-volatile read for the unstable but a
- * regular asm read for the stable.
- */
-#ifndef __smp_processor_id
-#define __smp_processor_id() raw_smp_processor_id()
-#endif
-
-#ifdef CONFIG_DEBUG_PREEMPT
-  extern unsigned int debug_smp_processor_id(void);
-# define smp_processor_id() debug_smp_processor_id()
-#else
 # define smp_processor_id() __smp_processor_id()
 #endif