[patch v3 09/36] x86/smpboot: Get rid of cpu_init_secondary()

Thomas Gleixner
2023-05-08T19:44:16Z

From: Thomas Gleixner <tglx@linutronix.de>

The synchronization of the AP with the control CPU is a SMP boot problem
and has nothing to do with cpu_init().

Open code cpu_init_secondary() in start_secondary() and move
wait_for_master_cpu() into the SMP boot code.

No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mikelley@microsoft.com>

---
arch/x86/include/asm/processor.h | 1 -
arch/x86/kernel/cpu/common.c | 27 ---------------------------
arch/x86/kernel/smpboot.c | 24 +++++++++++++++++++-----
3 files changed, 19 insertions(+), 33 deletions(-)
---

--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -551,7 +551,6 @@ extern void switch_gdt_and_percpu_base(i
extern void load_direct_gdt(int);
extern void load_fixmap_gdt(int);
extern void cpu_init(void);
-extern void cpu_init_secondary(void);
extern void cpu_init_exception_handling(void);
extern void cr4_init(void);

--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -2123,19 +2123,6 @@ static void dbg_restore_debug_regs(void)
#define dbg_restore_debug_regs()
#endif /* ! CONFIG_KGDB */

-static void wait_for_master_cpu(int cpu)
-{
-#ifdef CONFIG_SMP
- /*
- * wait for ACK from master CPU before continuing
- * with AP initialization
- */
- WARN_ON(cpumask_test_and_set_cpu(cpu, cpu_initialized_mask));
- while (!cpumask_test_cpu(cpu, cpu_callout_mask))
- cpu_relax();
-#endif
-}
-
static inline void setup_getcpu(int cpu)
{
unsigned long cpudata = vdso_encode_cpunode(cpu, early_cpu_to_node(cpu));
@@ -2239,8 +2226,6 @@ void cpu_init(void)
struct task_struct *cur = current;
int cpu = raw_smp_processor_id();

- wait_for_master_cpu(cpu);
-
ucode_cpu_init(cpu);

#ifdef CONFIG_NUMA
@@ -2293,18 +2278,6 @@ void cpu_init(void)
load_fixmap_gdt(cpu);
}

-#ifdef CONFIG_SMP
-void cpu_init_secondary(void)
-{
- /*
- * Relies on the BP having set-up the IDT tables, which are loaded
- * on this CPU in cpu_init_exception_handling().
- */
- cpu_init_exception_handling();
- cpu_init();
-}
-#endif
-
#ifdef CONFIG_MICROCODE_LATE_LOADING
/**
* store_cpu_caps() - Store a snapshot of CPU capabilities
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -220,6 +220,17 @@ static void ap_calibrate_delay(void)
cpu_data(smp_processor_id()).loops_per_jiffy = loops_per_jiffy;
}

+static void wait_for_master_cpu(int cpu)
+{
+ /*
+ * Wait for release by control CPU before continuing with AP
+ * initialization.
+ */
+ WARN_ON(cpumask_test_and_set_cpu(cpu, cpu_initialized_mask));
+ while (!cpumask_test_cpu(cpu, cpu_callout_mask))
+ cpu_relax();
+}
+
/*
* Activate a secondary processor.
*/
@@ -237,13 +248,16 @@ static void notrace start_secondary(void
load_cr3(swapper_pg_dir);
__flush_tlb_all();
#endif
+ cpu_init_exception_handling();
+
/*
- * Sync point with wait_cpu_initialized(). Before proceeding through
- * cpu_init(), the AP will call wait_for_master_cpu() which sets its
- * own bit in cpu_initialized_mask and then waits for the BSP to set
- * its bit in cpu_callout_mask to release it.
+ * Sync point with wait_cpu_initialized(). Sets AP in
+ * cpu_initialized_mask and then waits for the control CPU
+ * to release it.
*/
- cpu_init_secondary();
+ wait_for_master_cpu(raw_smp_processor_id());
+
+ cpu_init();
rcu_cpu_starting(raw_smp_processor_id());
x86_cpuinit.early_percpu_clock_init();