Re: [PATCH v9 09/11] seccomp: introduce writer locking

From: Oleg Nesterov
Date: Wed Jul 09 2014 - 15:01:39 EST


On 06/27, Kees Cook wrote:
>
> void put_seccomp_filter(struct task_struct *tsk)
> {
> - struct seccomp_filter *orig = tsk->seccomp.filter;
> + struct seccomp_filter *orig = smp_load_acquire(&tsk->seccomp.filter);
> /* Clean up single-reference branches iteratively. */
> while (orig && atomic_dec_and_test(&orig->usage)) {

And this smp_load_acquire() looks unnecessary. atomic_dec_and_test()
is a barrier.

Oleg.

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