x86: cpu_init(): fix memory leak when using CPU hotplug

Exception stacks are allocated each time a CPU is set online.
But the allocated space is never freed. Thus with one CPU hotplug
offline/online cycle there is a memory leak of 24K (6 pages) for
a CPU.

Fix is to allocate exception stacks only once -- when the CPU is
set online for the first time.

Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Cc: akpm@linux-foundation.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/arch/x86/kernel/cpu/common_64.c b/arch/x86/kernel/cpu/common_64.c
index 4f2eeb5..a11f5d4 100644 (file)
--- a/arch/x86/kernel/cpu/common_64.c
+++ b/arch/x86/kernel/cpu/common_64.c
@@ -640,19 +640,22 @@ void __cpuinit cpu_init(void)
        /*
         * set up and load the per-CPU TSS
         */
-       for (v = 0; v < N_EXCEPTION_STACKS; v++) {
+       if (!orig_ist->ist[0]) {
                static const unsigned int order[N_EXCEPTION_STACKS] = {
-                       [0 ... N_EXCEPTION_STACKS - 1] = EXCEPTION_STACK_ORDER,
-                       [DEBUG_STACK - 1] = DEBUG_STACK_ORDER
+                 [0 ... N_EXCEPTION_STACKS - 1] = EXCEPTION_STACK_ORDER,
+                 [DEBUG_STACK - 1] = DEBUG_STACK_ORDER
                };
-               if (cpu) {
-                       estacks = (char *)__get_free_pages(GFP_ATOMIC, order[v]);
-                       if (!estacks)
-                               panic("Cannot allocate exception stack %ld %d\n",
-                                     v, cpu);
+               for (v = 0; v < N_EXCEPTION_STACKS; v++) {
+                       if (cpu) {
+                               estacks = (char *)__get_free_pages(GFP_ATOMIC, order[v]);
+                               if (!estacks)
+                                       panic("Cannot allocate exception "
+                                             "stack %ld %d\n", v, cpu);
+                       }
+                       estacks += PAGE_SIZE << order[v];
+                       orig_ist->ist[v] = t->x86_tss.ist[v] =
+                                       (unsigned long)estacks;
                }
-               estacks += PAGE_SIZE << order[v];
-               orig_ist->ist[v] = t->x86_tss.ist[v] = (unsigned long)estacks;
        }
 
        t->x86_tss.io_bitmap_base = offsetof(struct tss_struct, io_bitmap);