On 12/03, Eric Dumazet wrote:
>
> Oleg Nesterov a ?crit :
>
> Yes, but how is it related to RCU ?
> I mean, rcu_do_batch() is just a loop like others in kernel.
> The loop itself is not buggy, but can call a buggy function, you are right.
int start_me_again;
struct rcu_head rcu_head;
void rcu_func(struct rcu_head *rcu)
{
start_me_again = 1;
}
// could be called on arbitrary CPU
void check_start_me_again(void)
{
static spinlock_t lock;
spin_lock(lock);
if (start_me_again) {
start_me_again = 0;
call_rcu(&rcu_head, rcu_func);
}
spin_unlock(lock);
}
I'd say this code is not buggy.
In case it was not clear. I do not claim we need this patch (I don't know).
And yes, I very much doubt we can hit this problem in practice (even if I am
right).
What I don't agree with is that it is callback which should take care of this
problem.
> A smp_rmb() wont avoid all possible bugs...
For example?
Oleg.
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