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Date: Sat, 11 Feb 2017 18:56:41 +0900
From: Hoeun Ryu <hoeun.ryu@...il.com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Michal Hocko <mhocko@...e.com>, Ingo Molnar <mingo@...nel.org>,
Andy Lutomirski <luto@...nel.org>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Oleg Nesterov <oleg@...hat.com>, Mateusz Guzik <mguzik@...hat.com>,
linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH v4] fork: free vmapped stacks in cache when cpus are offline
> On Feb 11, 2017, at 5:31 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
>
>> On Sat, 11 Feb 2017, Hoeun Ryu wrote:
>> #define NR_CACHED_STACKS 2
>> static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
>> +
>> +static int free_vm_stack_cache(unsigned int cpu)
>> +{
>> + struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
>> + int i;
>> +
>> + for (i = 0; i < NR_CACHED_STACKS; i++) {
>> + struct vm_struct *vm_stack = cached_vm_stacks[i];
>> +
>> + if (!vm_stack)
>> + continue;
>> +
>> + vfree(vm_stack->addr);
>> + cached_vm_stacks[i] = NULL;
>> + }
>> +
>> + return 0;
>> +}
>> #endif
>>
>> static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
>> @@ -456,6 +474,11 @@ void __init fork_init(void)
>> for (i = 0; i < UCOUNT_COUNTS; i++) {
>> init_user_ns.ucount_max[i] = max_threads/2;
>> }
>> +
>> +#ifdef CONFIG_VMAP_STACK
>> + cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vmstack_cache",
>> + NULL, free_vm_stack_cache);
>> +#endif
>
> If you wrap that in vm_stack_cache_init() and have a stub for !VMAP_STACK
> (add an #else to the #ifdef VMAP_STACK section above) then you spare the
> ugly ifdef in fork_init()
OK. I will.
> Thanks,
>
> tglx
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