x86: Use generic idle thread allocation

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: x86@kernel.org
Link: http://lkml.kernel.org/r/20120420124557.246929343@linutronix.de

4 files changed, 14 insertions, 84 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 1d14cc6b79ad..046bf4bd2510 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -82,6 +82,7 @@ config X86
         select ARCH_HAVE_NMI_SAFE_CMPXCHG
         select GENERIC_IOMAP
         select DCACHE_WORD_ACCESS if !DEBUG_PAGEALLOC
+        select GENERIC_SMP_IDLE_THREAD
 
 config INSTRUCTION_DECODER
         def_bool (KPROBES || PERF_EVENTS)
diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index f3ed33811c23..f8cbc6f20e31 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -164,6 +164,7 @@ int wbinvd_on_all_cpus(void);
 
 void native_send_call_func_ipi(const struct cpumask *mask);
 void native_send_call_func_single_ipi(int cpu);
+void x86_idle_thread_init(unsigned int cpu, struct task_struct *idle);
 
 void smp_store_cpu_info(int id);
 #define cpu_physical_id(cpu)    per_cpu(x86_cpu_to_apicid, cpu)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index def235bf7594..3acaf51dfddb 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -76,20 +76,8 @@
 /* State of each CPU */
 DEFINE_PER_CPU(int, cpu_state) = { 0 };
 
-/* Store all idle threads, this can be reused instead of creating
-* a new thread. Also avoids complicated thread destroy functionality
-* for idle threads.
-*/
 #ifdef CONFIG_HOTPLUG_CPU
 /*
- * Needed only for CONFIG_HOTPLUG_CPU because __cpuinitdata is
- * removed after init for !CONFIG_HOTPLUG_CPU.
- */
-static DEFINE_PER_CPU(struct task_struct *, idle_thread_array);
-#define get_idle_for_cpu(x)      (per_cpu(idle_thread_array, x))
-#define set_idle_for_cpu(x, p)   (per_cpu(idle_thread_array, x) = (p))
-
-/*
  * We need this for trampoline_base protection from concurrent accesses when
  * off- and onlining cores wildly.
  */
@@ -97,20 +85,16 @@ static DEFINE_MUTEX(x86_cpu_hotplug_driver_mutex);
 
 void cpu_hotplug_driver_lock(void)
 {
-        mutex_lock(&x86_cpu_hotplug_driver_mutex);
+        mutex_lock(&x86_cpu_hotplug_driver_mutex);
 }
 
 void cpu_hotplug_driver_unlock(void)
 {
-        mutex_unlock(&x86_cpu_hotplug_driver_mutex);
+        mutex_unlock(&x86_cpu_hotplug_driver_mutex);
 }
 
 ssize_t arch_cpu_probe(const char *buf, size_t count) { return -1; }
 ssize_t arch_cpu_release(const char *buf, size_t count) { return -1; }
-#else
-static struct task_struct *idle_thread_array[NR_CPUS] __cpuinitdata ;
-#define get_idle_for_cpu(x)      (idle_thread_array[(x)])
-#define set_idle_for_cpu(x, p)   (idle_thread_array[(x)] = (p))
 #endif
 
 /* Number of siblings per CPU package */
@@ -618,22 +602,6 @@ wakeup_secondary_cpu_via_init(int phys_apicid, unsigned long start_eip)
         return (send_status | accept_status);
 }
 
-struct create_idle {
-        struct work_struct work;
-        struct task_struct *idle;
-        struct completion done;
-        int cpu;
-};
-
-static void __cpuinit do_fork_idle(struct work_struct *work)
-{
-        struct create_idle *c_idle =
-                container_of(work, struct create_idle, work);
-
-        c_idle->idle = fork_idle(c_idle->cpu);
-        complete(&c_idle->done);
-}
-
 /* reduce the number of lines printed when booting a large cpu count system */
 static void __cpuinit announce_cpu(int cpu, int apicid)
 {
@@ -660,58 +628,31 @@ static void __cpuinit announce_cpu(int cpu, int apicid)
  * Returns zero if CPU booted OK, else error code from
  * ->wakeup_secondary_cpu.
  */
-static int __cpuinit do_boot_cpu(int apicid, int cpu)
+static int __cpuinit do_boot_cpu(int apicid, int cpu, struct task_struct *idle)
 {
         unsigned long boot_error = 0;
         unsigned long start_ip;
         int timeout;
-        struct create_idle c_idle = {
-                .cpu    = cpu,
-                .done   = COMPLETION_INITIALIZER_ONSTACK(c_idle.done),
-        };
-
-        INIT_WORK_ONSTACK(&c_idle.work, do_fork_idle);
 
         alternatives_smp_switch(1);
 
-        c_idle.idle = get_idle_for_cpu(cpu);
-
-        /*
-         * We can't use kernel_thread since we must avoid to
-         * reschedule the child.
-         */
-        if (c_idle.idle) {
-                c_idle.idle->thread.sp = (unsigned long) (((struct pt_regs *)
-                        (THREAD_SIZE +  task_stack_page(c_idle.idle))) - 1);
-                init_idle(c_idle.idle, cpu);
-                goto do_rest;
-        }
+        idle->thread.sp = (unsigned long) (((struct pt_regs *)
+                          (THREAD_SIZE +  task_stack_page(idle))) - 1);
+        per_cpu(current_task, cpu) = idle;
 
-        schedule_work(&c_idle.work);
-        wait_for_completion(&c_idle.done);
-
-        if (IS_ERR(c_idle.idle)) {
-                printk("failed fork for CPU %d\n", cpu);
-                destroy_work_on_stack(&c_idle.work);
-                return PTR_ERR(c_idle.idle);
-        }
-
-        set_idle_for_cpu(cpu, c_idle.idle);
-do_rest:
-        per_cpu(current_task, cpu) = c_idle.idle;
 #ifdef CONFIG_X86_32
         /* Stack for startup_32 can be just as for start_secondary onwards */
         irq_ctx_init(cpu);
 #else
-        clear_tsk_thread_flag(c_idle.idle, TIF_FORK);
+        clear_tsk_thread_flag(idle, TIF_FORK);
         initial_gs = per_cpu_offset(cpu);
         per_cpu(kernel_stack, cpu) =
-                (unsigned long)task_stack_page(c_idle.idle) -
+                (unsigned long)task_stack_page(idle) -
                 KERNEL_STACK_OFFSET + THREAD_SIZE;
 #endif
         early_gdt_descr.address = (unsigned long)get_cpu_gdt_table(cpu);
         initial_code = (unsigned long)start_secondary;
-        stack_start  = c_idle.idle->thread.sp;
+        stack_start  = idle->thread.sp;
 
         /* start_ip had better be page-aligned! */
         start_ip = trampoline_address();
@@ -813,8 +754,6 @@ do_rest:
                  */
                 smpboot_restore_warm_reset_vector();
         }
-
-        destroy_work_on_stack(&c_idle.work);
         return boot_error;
 }
 
@@ -851,7 +790,7 @@ int __cpuinit native_cpu_up(unsigned int cpu, struct task_struct *tidle)
 
         per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;
 
-        err = do_boot_cpu(apicid, cpu);
+        err = do_boot_cpu(apicid, cpu, tidle);
         if (err) {
                 pr_debug("do_boot_cpu failed %d\n", err);
                 return -EIO;
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 64d3bbce0b36..8f44cc1a9291 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -250,18 +250,8 @@ static void __init xen_smp_prepare_cpus(unsigned int max_cpus)
                 set_cpu_possible(cpu, false);
         }
 
-        for_each_possible_cpu (cpu) {
-                struct task_struct *idle;
-
-                if (cpu == 0)
-                        continue;
-
-                idle = fork_idle(cpu);
-                if (IS_ERR(idle))
-                        panic("failed fork for CPU %d", cpu);
-
+        for_each_possible_cpu(cpu)
                 set_cpu_present(cpu, true);
-        }
 }
 
 static int __cpuinit
@@ -331,9 +321,8 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
         return 0;
 }
 
-static int __cpuinit xen_cpu_up(unsigned int cpu, struct task_struct *tidle)
+static int __cpuinit xen_cpu_up(unsigned int cpu, struct task_struct *idle)
 {
-        struct task_struct *idle = idle_task(cpu);
         int rc;
 
         per_cpu(current_task, cpu) = idle;