On Thu, Jun 18, 2015 at 04:13:50PM +0530, Parav Pandit wrote:
> Kernel thread nvme_thread and driver load process can be executing
> in parallel on different CPU. This leads to race condition whenever
> nvme_alloc_queue() instructions are executed out of order that can
> reflects incorrect value for nvme_thread.
> Memory barrier in nvme_alloc_queue() ensures that it maintains the
> order and and data dependency read barrier in reader thread ensures
> that cpu cache is synced.
>
> Signed-off-by: Parav Pandit <parav.pan...@avagotech.com>
> ---
> drivers/block/nvme-core.c | 12 ++++++++++--
> 1 files changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/block/nvme-core.c b/drivers/block/nvme-core.c
> index 5961ed7..90fb0ce 100644
> --- a/drivers/block/nvme-core.c
> +++ b/drivers/block/nvme-core.c
> @@ -1403,8 +1403,10 @@ static struct nvme_queue *nvme_alloc_queue(struct
> nvme_dev *dev, int qid,
> nvmeq->q_db = &dev->dbs[qid * 2 * dev->db_stride];
> nvmeq->q_depth = depth;
> nvmeq->qid = qid;
> - dev->queue_count++;
> dev->queues[qid] = nvmeq;
> + /* update queues first before updating queue_count */
> + smp_wmb();
> + dev->queue_count++;
>
> return nvmeq;
>
This has been applied already as an explicit mb()
> @@ -2073,7 +2075,13 @@ static int nvme_kthread(void *data)
> continue;
> }
> for (i = 0; i < dev->queue_count; i++) {
> - struct nvme_queue *nvmeq = dev->queues[i];
> + struct nvme_queue *nvmeq;
> +
> + /* make sure to read queue_count before
> + * traversing queues.
> + */
> + smp_read_barrier_depends();
> + nvmeq = dev->queues[i];
> if (!nvmeq)
> continue;
> spin_lock_irq(&nvmeq->q_lock);
I don't think this is necessary. If queue_count is incremented while in this
loop, it will be picked up the next time the kthread runs
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
