From: Yishai Hadas <yishaih@dev.mellanox.co.il>
To: Jason Gunthorpe <jgg@mellanox.com>
Cc: Leon Romanovsky <leon@kernel.org>,
Doug Ledford <dledford@redhat.com>,
Leon Romanovsky <leonro@mellanox.com>,
RDMA mailing list <linux-rdma@vger.kernel.org>,
Yishai Hadas <yishaih@mellanox.com>,
Saeed Mahameed <saeedm@mellanox.com>,
linux-netdev <netdev@vger.kernel.org>
Subject: Re: [PATCH rdma-next v1 11/12] IB/mlx5: Implement DEVX dispatching event
Date: Tue, 25 Jun 2019 17:41:49 +0300 [thread overview]
Message-ID: <a2380ea6-4542-c72c-96f7-e68786847ccc@dev.mellanox.co.il> (raw)
In-Reply-To: <20190624180558.GL7418@mellanox.com>
On 6/24/2019 9:06 PM, Jason Gunthorpe wrote:
> On Mon, Jun 24, 2019 at 07:55:32PM +0300, Yishai Hadas wrote:
>
>>>> + /* Explicit filtering to kernel events which may occur frequently */
>>>> + if (event_type == MLX5_EVENT_TYPE_CMD ||
>>>> + event_type == MLX5_EVENT_TYPE_PAGE_REQUEST)
>>>> + return NOTIFY_OK;
>>>> +
>>>> + table = container_of(nb, struct mlx5_devx_event_table, devx_nb.nb);
>>>> + dev = container_of(table, struct mlx5_ib_dev, devx_event_table);
>>>> + is_unaffiliated = is_unaffiliated_event(dev->mdev, event_type);
>>>> +
>>>> + if (!is_unaffiliated)
>>>> + obj_type = get_event_obj_type(event_type, data);
>>>> + event = xa_load(&table->event_xa, event_type | (obj_type << 16));
>>>> + if (!event)
>>>> + return NOTIFY_DONE;
>>>
>>> event should be in the rcu as well
>>
>> Do we really need this ? I didn't see a flow that really requires
>> that.
>
> I think there are no frees left? Even so it makes much more sense to
> include the event in the rcu as if we ever did need to kfree it would
> have to be via rcu
>
OK
>>>> + while (list_empty(&ev_queue->event_list)) {
>>>> + spin_unlock_irq(&ev_queue->lock);
>>>> +
>>>> + if (filp->f_flags & O_NONBLOCK)
>>>> + return -EAGAIN;
>>>> +
>>>> + if (wait_event_interruptible(ev_queue->poll_wait,
>>>> + (!list_empty(&ev_queue->event_list) ||
>>>> + ev_queue->is_destroyed))) {
>>>> + return -ERESTARTSYS;
>>>> + }
>>>> +
>>>> + if (list_empty(&ev_queue->event_list) &&
>>>> + ev_queue->is_destroyed)
>>>> + return -EIO;
>>>
>>> All these tests should be under the lock.
>>
>> We can't call wait_event_interruptible() above which may sleep under the
>> lock, correct ? are you referring to the list_empty() and
>> is_destroyed ?
>
> yes
>
>> By the way looking in uverb code [1], similar code which is not done under
>> the lock as of here..
>>
>> [1] https://elixir.bootlin.com/linux/latest/source/drivers/infiniband/core/uverbs_main.c#L244
>
> Also not a good idea
>
>>> Why don't we return EIO as soon as is-destroyed happens? What is the
>>> point of flushing out the accumulated events?
>>
>> It follows the above uverb code/logic that returns existing events even in
>> that case, also the async command events in this file follows that logic, I
>> suggest to stay consistent.
>
> Don't follow broken uverbs stuff...
May it be that there is some event that we still want to deliver post
unbind/hot-unplug ? for example IB_EVENT_DEVICE_FATAL in uverbs and
others from the driver code.
Not sure that we want to change this logic.
What do you think ?
>
>>> Maybe the event should be re-added on error? Tricky.
>>
>> What will happen if another copy_to_user may then fail again (loop ?) ...
>> not sure that we want to get into this tricky handling ...
>>
>> As of above, It follows the logic from uverbs at that area.
>> https://elixir.bootlin.com/linux/latest/source/drivers/infiniband/core/uverbs_main.c#L267
>
> again it is wrong...
>
> There is no loop if you just stick the item back on the head of the
> list and exit, which is probably the right thing to do..
>
What if copy_to_user() will fail again just later on ? we might end-up
with loop of read(s) that always find an event as it was put back.
I suggest to leave this flow as it's now, at least for this series
submission.
Agree ?
>>>> @@ -2374,6 +2705,17 @@ static int devx_hot_unplug_async_cmd_event_file(struct ib_uobject *uobj,
>>>> static int devx_hot_unplug_async_event_file(struct ib_uobject *uobj,
>>>> enum rdma_remove_reason why)
>>>> {
>>>> + struct devx_async_event_file *ev_file =
>>>> + container_of(uobj, struct devx_async_event_file,
>>>> + uobj);
>>>> + struct devx_async_event_queue *ev_queue = &ev_file->ev_queue;
>>>> +
>>>> + spin_lock_irq(&ev_queue->lock);
>>>> + ev_queue->is_destroyed = 1;
>>>> + spin_unlock_irq(&ev_queue->lock);
>>>> +
>>>> + if (why == RDMA_REMOVE_DRIVER_REMOVE)
>>>> + wake_up_interruptible(&ev_queue->poll_wait);
>>>
>>> Why isn't this wakeup always done?
>>
>> Maybe you are right and this can be always done to wake up any readers as
>> the 'is_destroyed' was set.
>>
>> By the way, any idea why it was done as such in uverbs [1] for similar flow
>> ? also the command events follows that.
>
> I don't know, it is probably pointless too.
>
> If we don't need it here then we shouldn't have it.
>
> These random pointless ifs bother me as we have to spend time trying
> to figure out that they are pointless down the road.
>
OK, will drop this if.
next prev parent reply other threads:[~2019-06-25 14:41 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-18 17:15 [PATCH rdma-next v1 00/12] DEVX asynchronous events Leon Romanovsky
2019-06-18 17:15 ` [PATCH mlx5-next v1 01/12] net/mlx5: Fix mlx5_core_destroy_cq() error flow Leon Romanovsky
2019-06-18 17:15 ` [PATCH mlx5-next v1 02/12] net/mlx5: Use event mask based on device capabilities Leon Romanovsky
2019-06-27 0:23 ` Saeed Mahameed
2019-06-18 17:15 ` [PATCH mlx5-next v1 03/12] net/mlx5: Expose the API to register for ANY event Leon Romanovsky
2019-06-18 17:15 ` [PATCH mlx5-next v1 04/12] net/mlx5: mlx5_core_create_cq() enhancements Leon Romanovsky
2019-06-18 17:15 ` [PATCH mlx5-next v1 05/12] net/mlx5: Report a CQ error event only when a handler was set Leon Romanovsky
2019-06-18 17:15 ` [PATCH mlx5-next v1 06/12] net/mlx5: Report EQE data upon CQ completion Leon Romanovsky
2019-06-18 17:15 ` [PATCH mlx5-next v1 07/12] net/mlx5: Expose device definitions for object events Leon Romanovsky
2019-06-18 17:15 ` [PATCH rdma-next v1 08/12] IB/mlx5: Introduce MLX5_IB_OBJECT_DEVX_ASYNC_EVENT_FD Leon Romanovsky
2019-06-24 11:51 ` Jason Gunthorpe
2019-06-24 13:25 ` Yishai Hadas
2019-06-24 14:30 ` Jason Gunthorpe
2019-06-18 17:15 ` [PATCH rdma-next v1 09/12] IB/mlx5: Register DEVX with mlx5_core to get async events Leon Romanovsky
2019-06-24 11:52 ` Jason Gunthorpe
2019-06-24 13:36 ` Yishai Hadas
2019-06-24 14:30 ` Jason Gunthorpe
2019-06-18 17:15 ` [PATCH rdma-next v1 10/12] IB/mlx5: Enable subscription for device events over DEVX Leon Romanovsky
2019-06-24 11:57 ` Jason Gunthorpe
2019-06-24 16:13 ` Yishai Hadas
2019-06-24 17:56 ` Jason Gunthorpe
2019-06-18 17:15 ` [PATCH rdma-next v1 11/12] IB/mlx5: Implement DEVX dispatching event Leon Romanovsky
2019-06-24 12:03 ` Jason Gunthorpe
2019-06-24 16:55 ` Yishai Hadas
2019-06-24 18:06 ` Jason Gunthorpe
2019-06-25 14:41 ` Yishai Hadas [this message]
2019-06-25 20:23 ` Jason Gunthorpe
2019-06-18 17:15 ` [PATCH rdma-next v1 12/12] IB/mlx5: Add DEVX support for CQ events Leon Romanovsky
2019-06-24 12:04 ` Jason Gunthorpe
2019-06-24 17:03 ` Yishai Hadas
2019-06-24 18:06 ` Jason Gunthorpe
2019-06-18 18:51 ` [PATCH rdma-next v1 00/12] DEVX asynchronous events Saeed Mahameed
2019-06-19 4:45 ` Leon Romanovsky
2019-06-24 21:57 ` Saeed Mahameed
2019-06-30 8:53 ` Leon Romanovsky
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