On 8/21/19 6:28 PM, Ming Lei wrote:
On Wed, Aug 21, 2019 at 09:18:08AM -0700, Bart Van Assche wrote:
On 8/21/19 2:15 AM, Ming Lei wrote:
diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
index 31bbf10d8149..a4cc40ddda86 100644
--- a/block/blk-mq-sysfs.c
+++ b/block/blk-mq-sysfs.c
@@ -247,7 +247,7 @@ void blk_mq_unregister_dev(struct device *dev, struct request_queue *q)
struct blk_mq_hw_ctx *hctx;
int i;
- lockdep_assert_held(&q->sysfs_lock);
+ lockdep_assert_held(&q->sysfs_dir_lock);
queue_for_each_hw_ctx(q, hctx, i)
blk_mq_unregister_hctx(hctx);
@@ -297,7 +297,7 @@ int __blk_mq_register_dev(struct device *dev, struct request_queue *q)
int ret, i;
WARN_ON_ONCE(!q->kobj.parent);
- lockdep_assert_held(&q->sysfs_lock);
+ lockdep_assert_held(&q->sysfs_dir_lock);
ret = kobject_add(q->mq_kobj, kobject_get(&dev->kobj), "%s", "mq");
if (ret < 0)
blk_mq_unregister_dev and __blk_mq_register_dev() are only used by
blk_register_queue() and blk_unregister_queue(). It is the responsibility of
the callers of these function to serialize request queue registration and
unregistration. Is it really necessary to hold a mutex around the
blk_mq_unregister_dev and __blk_mq_register_dev() calls? Or in other words,
can it ever happen that multiple threads invoke one or both functions
concurrently?
hctx kobjects can be removed and re-added via blk_mq_update_nr_hw_queues()
which may be called at the same time when queue is registering or
un-registering.
Shouldn't blk_register_queue() and blk_unregister_queue() be serialized
against blk_mq_update_nr_hw_queues()? Allowing these calls to proceed
concurrently complicates the block layer and makes the block layer code
harder to review than necessary. I don't think that it would help any
block driver to allow these calls to proceed concurrently.
Thanks,
Bart.
