[S390] Allocate and free cpu lowcores and stacks when needed/possible.

No need to preallocate the per cpu lowcores and stacks.
Savings are 28-32k per offline cpu.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index d300a7fdf71127d60147d637137891fe0f3cdbe1..040406dbe9aa851ef971c563d24deb1ff21c08fb 100644 (file)
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -589,8 +589,72 @@ static void __init smp_create_idle(unsigned int cpu)
        spin_lock_init(&(&per_cpu(s390_idle, cpu))->lock);
 }
 
+static int __cpuinit smp_alloc_lowcore(int cpu)
+{
+       unsigned long async_stack, panic_stack;
+       struct _lowcore *lowcore;
+       int lc_order;
+
+       lc_order = sizeof(long) == 8 ? 1 : 0;
+       lowcore = (void *) __get_free_pages(GFP_KERNEL | GFP_DMA, lc_order);
+       if (!lowcore)
+               return -ENOMEM;
+       async_stack = __get_free_pages(GFP_KERNEL, ASYNC_ORDER);
+       if (!async_stack)
+               goto out_async_stack;
+       panic_stack = __get_free_page(GFP_KERNEL);
+       if (!panic_stack)
+               goto out_panic_stack;
+
+       *lowcore = S390_lowcore;
+       lowcore->async_stack = async_stack + ASYNC_SIZE;
+       lowcore->panic_stack = panic_stack + PAGE_SIZE;
+
+#ifndef CONFIG_64BIT
+       if (MACHINE_HAS_IEEE) {
+               unsigned long save_area;
+
+               save_area = get_zeroed_page(GFP_KERNEL);
+               if (!save_area)
+                       goto out_save_area;
+               lowcore->extended_save_area_addr = (u32) save_area;
+       }
+#endif
+       lowcore_ptr[cpu] = lowcore;
+       return 0;
+
+#ifndef CONFIG_64BIT
+out_save_area:
+       free_page(panic_stack);
+#endif
+out_panic_stack:
+       free_pages(async_stack, ASYNC_ORDER);
+out_async_stack:
+       free_pages((unsigned long) lowcore, lc_order);
+       return -ENOMEM;
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+static void smp_free_lowcore(int cpu)
+{
+       struct _lowcore *lowcore;
+       int lc_order;
+
+       lc_order = sizeof(long) == 8 ? 1 : 0;
+       lowcore = lowcore_ptr[cpu];
+#ifndef CONFIG_64BIT
+       if (MACHINE_HAS_IEEE)
+               free_page((unsigned long) lowcore->extended_save_area_addr);
+#endif
+       free_page(lowcore->panic_stack - PAGE_SIZE);
+       free_pages(lowcore->async_stack - ASYNC_SIZE, ASYNC_ORDER);
+       free_pages((unsigned long) lowcore, lc_order);
+       lowcore_ptr[cpu] = NULL;
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+
 /* Upping and downing of CPUs */
-int __cpu_up(unsigned int cpu)
+int __cpuinit __cpu_up(unsigned int cpu)
 {
        struct task_struct *idle;
        struct _lowcore *cpu_lowcore;
@@ -599,6 +663,8 @@ int __cpu_up(unsigned int cpu)
 
        if (smp_cpu_state[cpu] != CPU_STATE_CONFIGURED)
                return -EIO;
+       if (smp_alloc_lowcore(cpu))
+               return -ENOMEM;
 
        ccode = signal_processor_p((__u32)(unsigned long)(lowcore_ptr[cpu]),
                                   cpu, sigp_set_prefix);
@@ -613,6 +679,7 @@ int __cpu_up(unsigned int cpu)
        cpu_lowcore = lowcore_ptr[cpu];
        cpu_lowcore->kernel_stack = (unsigned long)
                task_stack_page(idle) + THREAD_SIZE;
+       cpu_lowcore->thread_info = (unsigned long) task_thread_info(idle);
        sf = (struct stack_frame *) (cpu_lowcore->kernel_stack
                                     - sizeof(struct pt_regs)
                                     - sizeof(struct stack_frame));
@@ -626,6 +693,8 @@ int __cpu_up(unsigned int cpu)
        cpu_lowcore->percpu_offset = __per_cpu_offset[cpu];
        cpu_lowcore->current_task = (unsigned long) idle;
        cpu_lowcore->cpu_data.cpu_nr = cpu;
+       cpu_lowcore->softirq_pending = 0;
+       cpu_lowcore->ext_call_fast = 0;
        eieio();
 
        while (signal_processor(cpu, sigp_restart) == sigp_busy)
@@ -686,6 +755,7 @@ void __cpu_die(unsigned int cpu)
        /* Wait until target cpu is down */
        while (!smp_cpu_not_running(cpu))
                cpu_relax();
+       smp_free_lowcore(cpu);
        printk(KERN_INFO "Processor %d spun down\n", cpu);
 }
 
@@ -699,15 +769,9 @@ void cpu_die(void)
 
 #endif /* CONFIG_HOTPLUG_CPU */
 
-/*
- *     Cycle through the processors and setup structures.
- */
-
 void __init smp_prepare_cpus(unsigned int max_cpus)
 {
-       unsigned long stack;
        unsigned int cpu;
-       int i;
 
        smp_detect_cpus();
 
@@ -715,35 +779,9 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
        if (register_external_interrupt(0x1201, do_ext_call_interrupt) != 0)
                panic("Couldn't request external interrupt 0x1201");
        memset(lowcore_ptr, 0, sizeof(lowcore_ptr));
-       /*
-        *  Initialize prefix pages and stacks for all possible cpus
-        */
        print_cpu_info(&S390_lowcore.cpu_data);
+       smp_alloc_lowcore(smp_processor_id());
 
-       for_each_possible_cpu(i) {
-               lowcore_ptr[i] = (struct _lowcore *)
-                       __get_free_pages(GFP_KERNEL | GFP_DMA,
-                                        sizeof(void*) == 8 ? 1 : 0);
-               stack = __get_free_pages(GFP_KERNEL, ASYNC_ORDER);
-               if (!lowcore_ptr[i] || !stack)
-                       panic("smp_boot_cpus failed to allocate memory\n");
-
-               *(lowcore_ptr[i]) = S390_lowcore;
-               lowcore_ptr[i]->async_stack = stack + ASYNC_SIZE;
-               stack = __get_free_pages(GFP_KERNEL, 0);
-               if (!stack)
-                       panic("smp_boot_cpus failed to allocate memory\n");
-               lowcore_ptr[i]->panic_stack = stack + PAGE_SIZE;
-#ifndef CONFIG_64BIT
-               if (MACHINE_HAS_IEEE) {
-                       lowcore_ptr[i]->extended_save_area_addr =
-                               (__u32) __get_free_pages(GFP_KERNEL, 0);
-                       if (!lowcore_ptr[i]->extended_save_area_addr)
-                               panic("smp_boot_cpus failed to "
-                                     "allocate memory\n");
-               }
-#endif
-       }
 #ifndef CONFIG_64BIT
        if (MACHINE_HAS_IEEE)
                ctl_set_bit(14, 29); /* enable extended save area */