Re: [PATCH v2 2/2] block: Fix a race between the throttling code and request queue initialization

[Bart Van Assche]

On Fri, 2018-02-02 at 09:02 +0800, Joseph Qi wrote:
> We triggered this race when using single queue. I'm not sure if it
> exists in multi-queue.

Regarding the races between modifying the queue_lock pointer and the code that
uses that pointer, I think the following construct in blk_cleanup_queue() is
sufficient to avoid races between the queue_lock pointer assignment and the code
that executes concurrently with blk_cleanup_queue():

        spin_lock_irq(lock);
        if (q->queue_lock != &q->__queue_lock)
                q->queue_lock = &q->__queue_lock;
        spin_unlock_irq(lock);

In other words, I think that this patch series should be sufficient to address
all races between .queue_lock assignments and the code that uses that pointer.

Thanks,

Bart.