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From: Jason Gunthorpe <jgg@mellanox.com>
To: Yishai Hadas <yishaih@dev.mellanox.co.il>
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 20:23:24 +0000
Message-ID: <20190625202320.GJ3607@mellanox.com> (raw)
In-Reply-To: <a2380ea6-4542-c72c-96f7-e68786847ccc@dev.mellanox.co.il>

On Tue, Jun 25, 2019 at 05:41:49PM +0300, Yishai Hadas wrote:
> > > > 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.

EIO is DEVICE_FATAL.

> Not sure that we want to change this logic.
> What do you think ?

I think this code should exit immediately with EIO if the device is
disassociated.

> > > > 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.

That is clearly an application bug and is not the concern of the
kernel..

> I suggest to leave this flow as it's now, at least for this series
> submission.
> 
> Agree ?

I don't think you can actually fix this, so maybe we have to leave
it. But add a comment explaining 

Jason

  reply index

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
2019-06-25 20:23           ` Jason Gunthorpe [this message]
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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