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Subject[PATCH 2/2] 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>
---
arch/x86/kernel/cpu/common_64.c | 23 +++++++++++++----------
1 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/cpu/common_64.c b/arch/x86/kernel/cpu/common_64.c
index c941397..a5b9600 100644
--- a/arch/x86/kernel/cpu/common_64.c
+++ b/arch/x86/kernel/cpu/common_64.c
@@ -604,19 +604,22 @@ 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);
--
1.5.6.4




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