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;
@@ -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);
--
1.7.1
--
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