Merge branch 'x86-percpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'x86-percpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  x86, percpu: Collect hot percpu variables into one cacheline
  x86, percpu: Fix DECLARE/DEFINE_PER_CPU_PAGE_ALIGNED()
  x86, percpu: Add 'percpu_read_stable()' interface for cacheable accesses

1 files changed, 14 insertions, 4 deletions

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 55a6abe4039..2055fc2b2e6 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -987,13 +987,21 @@ struct desc_ptr idt_descr = { NR_VECTORS * 16 - 1, (unsigned long) idt_table };
 DEFINE_PER_CPU_FIRST(union irq_stack_union,
                      irq_stack_union) __aligned(PAGE_SIZE);
 
-DEFINE_PER_CPU(char *, irq_stack_ptr) =
-        init_per_cpu_var(irq_stack_union.irq_stack) + IRQ_STACK_SIZE - 64;
+/*
+ * The following four percpu variables are hot.  Align current_task to
+ * cacheline size such that all four fall in the same cacheline.
+ */
+DEFINE_PER_CPU(struct task_struct *, current_task) ____cacheline_aligned =
+        &init_task;
+EXPORT_PER_CPU_SYMBOL(current_task);
 
 DEFINE_PER_CPU(unsigned long, kernel_stack) =
         (unsigned long)&init_thread_union - KERNEL_STACK_OFFSET + THREAD_SIZE;
 EXPORT_PER_CPU_SYMBOL(kernel_stack);
 
+DEFINE_PER_CPU(char *, irq_stack_ptr) =
+        init_per_cpu_var(irq_stack_union.irq_stack) + IRQ_STACK_SIZE - 64;
+
 DEFINE_PER_CPU(unsigned int, irq_count) = -1;
 
 /*
@@ -1008,8 +1016,7 @@ static const unsigned int exception_stack_sizes[N_EXCEPTION_STACKS] = {
 };
 
 static DEFINE_PER_CPU_PAGE_ALIGNED(char, exception_stacks
-        [(N_EXCEPTION_STACKS - 1) * EXCEPTION_STKSZ + DEBUG_STKSZ])
-        __aligned(PAGE_SIZE);
+        [(N_EXCEPTION_STACKS - 1) * EXCEPTION_STKSZ + DEBUG_STKSZ]);
 
 /* May not be marked __init: used by software suspend */
 void syscall_init(void)
@@ -1042,6 +1049,9 @@ DEFINE_PER_CPU(struct orig_ist, orig_ist);
 
 #else   /* CONFIG_X86_64 */
 
+DEFINE_PER_CPU(struct task_struct *, current_task) = &init_task;
+EXPORT_PER_CPU_SYMBOL(current_task);
+
 #ifdef CONFIG_CC_STACKPROTECTOR
 DEFINE_PER_CPU_ALIGNED(struct stack_canary, stack_canary);
 #endif