[patch V4 14/37] x86/smpboot: Remove cpu_callin_mask

[Thomas Gleixner <tglx@xxxxxxxxxxxxx>]

From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

Now that TSC synchronization is SMP function call based there is no reason
to wait for the AP to be set in smp_callin_mask. The control CPU waits for
the AP to set itself in the online mask anyway.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Tested-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
---
V4: Rename smp_callin() to ap_starting() - Peter Z.
---
 arch/x86/kernel/smpboot.c |   74 +++++++++-------------------------------------
 1 file changed, 15 insertions(+), 59 deletions(-)

--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -104,7 +104,6 @@ EXPORT_PER_CPU_SYMBOL(cpu_info);
 /* All of these masks are initialized in setup_cpu_local_masks() */
 static cpumask_var_t cpu_initialized_mask;
 static cpumask_var_t cpu_callout_mask;
-static cpumask_var_t cpu_callin_mask;
 /* Representing CPUs for which sibling maps can be computed */
 static cpumask_var_t cpu_sibling_setup_mask;
 
@@ -161,38 +160,30 @@ static inline void smpboot_restore_warm_
 
 }
 
-/*
- * Report back to the Boot Processor during boot time or to the caller 
processor
- * during CPU online.
- */
-static void smp_callin(void)
+/* Run the next set of setup steps for the upcoming CPU */
+static void ap_starting(void)
 {
-       int cpuid;
-
-       /*
-        * If waken up by an INIT in an 82489DX configuration
-        * cpu_callout_mask guarantees we don't get here before
-        * an INIT_deassert IPI reaches our local APIC, so it is
-        * now safe to touch our local APIC.
-        */
-       cpuid = smp_processor_id();
+       int cpuid = smp_processor_id();
 
        /*
-        * the boot CPU has finished the init stage and is spinning
-        * on callin_map until we finish. We are free to set up this
-        * CPU, first the APIC. (this is probably redundant on most
-        * boards)
+        * If woken up by an INIT in an 82489DX configuration
+        * cpu_callout_mask guarantees the CPU does not reach this point
+        * before an INIT_deassert IPI reaches the local APIC, so it is now
+        * safe to touch the local APIC.
+        *
+        * Set up this CPU, first the APIC, which is probably redundant on
+        * most boards.
         */
        apic_ap_setup();
 
-       /* Save our processor parameters. */
+       /* Save the processor parameters. */
        smp_store_cpu_info(cpuid);
 
        /*
         * The topology information must be up to date before
         * notify_cpu_starting().
         */
-       set_cpu_sibling_map(raw_smp_processor_id());
+       set_cpu_sibling_map(cpuid);
 
        ap_init_aperfmperf();
 
@@ -205,11 +196,6 @@ static void smp_callin(void)
         * state CPUHP_ONLINE.
         */
        notify_cpu_starting(cpuid);
-
-       /*
-        * Allow the master to continue.
-        */
-       cpumask_set_cpu(cpuid, cpu_callin_mask);
 }
 
 static void ap_calibrate_delay(void)
@@ -268,12 +254,7 @@ static void notrace start_secondary(void
        rcu_cpu_starting(raw_smp_processor_id());
        x86_cpuinit.early_percpu_clock_init();
 
-       /*
-        * Sync point with wait_cpu_callin(). The AP doesn't wait here
-        * but just sets the bit to let the controlling CPU (BSP) know that
-        * it's got this far.
-        */
-       smp_callin();
+       ap_starting();
 
        /* Check TSC synchronization with the control CPU. */
        check_tsc_sync_target();
@@ -1109,7 +1090,7 @@ static int wait_cpu_cpumask(unsigned int
  * and thus wait_for_master_cpu(), then set cpu_callout_mask to allow it
  * to proceed.  The AP will then proceed past setting its 'callin' bit
  * and end up waiting in check_tsc_sync_target() until we reach
- * do_wait_cpu_online() to tend to it.
+ * wait_cpu_online() to tend to it.
  */
 static int wait_cpu_initialized(unsigned int cpu)
 {
@@ -1124,20 +1105,7 @@ static int wait_cpu_initialized(unsigned
 }
 
 /*
- * Bringup step three: Wait for the target AP to reach smp_callin().
- * The AP is not waiting for us here so we don't need to parallelise
- * this step. Not entirely clear why we care about this, since we just
- * proceed directly to TSC synchronization which is the next sync
- * point with the AP anyway.
- */
-static void wait_cpu_callin(unsigned int cpu)
-{
-       while (!cpumask_test_cpu(cpu, cpu_callin_mask))
-               schedule();
-}
-
-/*
- * Bringup step four: Wait for the target AP to reach set_cpu_online() in
+ * Bringup step three: Wait for the target AP to reach set_cpu_online() in
  * start_secondary().
  */
 static void wait_cpu_online(unsigned int cpu)
@@ -1167,14 +1135,6 @@ static int native_kick_ap(unsigned int c
        }
 
        /*
-        * Already booted CPU?
-        */
-       if (cpumask_test_cpu(cpu, cpu_callin_mask)) {
-               pr_debug("do_boot_cpu %d Already started\n", cpu);
-               return -ENOSYS;
-       }
-
-       /*
         * Save current MTRR state in case it was changed since early boot
         * (e.g. by the ACPI SMI) to initialize new CPUs with MTRRs in sync:
         */
@@ -1211,7 +1171,6 @@ int native_cpu_up(unsigned int cpu, stru
        if (ret)
                goto out;
 
-       wait_cpu_callin(cpu);
        wait_cpu_online(cpu);
 
 out:
@@ -1327,7 +1286,6 @@ void __init smp_prepare_cpus_common(void
         * Setup boot CPU information
         */
        smp_store_boot_cpu_info(); /* Final full version of the data */
-       cpumask_copy(cpu_callin_mask, cpumask_of(0));
        mb();
 
        for_each_possible_cpu(i) {
@@ -1542,7 +1500,6 @@ early_param("possible_cpus", _setup_poss
 void __init setup_cpu_local_masks(void)
 {
        alloc_bootmem_cpumask_var(&cpu_initialized_mask);
-       alloc_bootmem_cpumask_var(&cpu_callin_mask);
        alloc_bootmem_cpumask_var(&cpu_callout_mask);
        alloc_bootmem_cpumask_var(&cpu_sibling_setup_mask);
 }
@@ -1606,7 +1563,6 @@ static void remove_cpu_from_maps(int cpu
 {
        set_cpu_online(cpu, false);
        cpumask_clear_cpu(cpu, cpu_callout_mask);
-       cpumask_clear_cpu(cpu, cpu_callin_mask);
        /* was set by cpu_init() */
        cpumask_clear_cpu(cpu, cpu_initialized_mask);
        numa_remove_cpu(cpu);