On Fri, 22 May 2015, Parav Pandit wrote:
I agree to it that nvmeq won't be null after mb(); That alone is not sufficient.
What I have proposed in previous email is,
Converting,
struct nvme_queue *nvmeq = dev->queues[i];
if (!nvmeq)
continue;
spin_lock_irq(nvmeq->q_lock);
to replace with,
struct nvme_queue *nvmeq = rcu_dereference(dev->queues[i]);
if (!nvmeq)
continue;
spin_lock_irq(nvmeq->q_lock);
This will prevent fetching content of q_lock before checking for NULL
condition. Classic usage or RCU.
What the heck are you talking about? The value of dev->queue_count won't
even let the thread iterate an nvmeq before q_lock is initialized.
We used to rcu protect queue access, but that was to make nvme's
make_request_fn safe to surprise removal, not for the polling thread.
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