x86-64: Convert irqstacks to per-cpu

Move the irqstackptr variable from the PDA to per-cpu.  Make the
stacks themselves per-cpu, removing some specific allocation code.
Add a seperate flag (is_boot_cpu) to simplify the per-cpu boot
adjustments.

tj: * sprinkle some underbars around.

    * irq_stack_ptr is not used till traps_init(), no reason to
      initialize it early.  On SMP, just leaving it NULL till proper
      initialization in setup_per_cpu_areas() works.  Dropped
      is_boot_cpu and early irq_stack_ptr initialization.

    * do DECLARE/DEFINE_PER_CPU(char[IRQ_STACK_SIZE], irq_stack)
      instead of (char, irq_stack[IRQ_STACK_SIZE]).

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 7 insertions, 12 deletions

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 3d0cc6f17116..496f0a01919b 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -881,7 +881,13 @@ __setup("clearcpuid=", setup_disablecpuid);
 #ifdef CONFIG_X86_64
 struct desc_ptr idt_descr = { 256 * 16 - 1, (unsigned long) idt_table };
 
-static char boot_cpu_stack[IRQSTACKSIZE] __page_aligned_bss;
+DEFINE_PER_CPU_PAGE_ALIGNED(char[IRQ_STACK_SIZE], irq_stack);
+#ifdef CONFIG_SMP
+DEFINE_PER_CPU(char *, irq_stack_ptr);  /* will be set during per cpu init */
+#else
+DEFINE_PER_CPU(char *, irq_stack_ptr) =
+        per_cpu_var(irq_stack) + IRQ_STACK_SIZE - 64;
+#endif
 
 void __cpuinit pda_init(int cpu)
 {
@@ -901,18 +907,7 @@ void __cpuinit pda_init(int cpu)
         if (cpu == 0) {
                 /* others are initialized in smpboot.c */
                 pda->pcurrent = &init_task;
-                pda->irqstackptr = boot_cpu_stack;
-                pda->irqstackptr += IRQSTACKSIZE - 64;
         } else {
-                if (!pda->irqstackptr) {
-                        pda->irqstackptr = (char *)
-                                __get_free_pages(GFP_ATOMIC, IRQSTACK_ORDER);
-                        if (!pda->irqstackptr)
-                                panic("cannot allocate irqstack for cpu %d",
-                                      cpu);
-                        pda->irqstackptr += IRQSTACKSIZE - 64;
-                }
-
                 if (pda->nodenumber == 0 && cpu_to_node(cpu) != NUMA_NO_NODE)
                         pda->nodenumber = cpu_to_node(cpu);
         }