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Date: Sat, 11 Feb 2017 09:31:31 +0100 (CET)
From: Thomas Gleixner <tglx@...utronix.de>
To: Hoeun Ryu <hoeun.ryu@...il.com>
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 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()
Thanks,
tglx
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