From: Jiri Pirko <jiri@resnulli.us>
To: Jakub Kicinski <kuba@kernel.org>
Cc: davem@davemloft.net, netdev@vger.kernel.org, edumazet@google.com,
pabeni@redhat.com, jacob.e.keller@intel.com
Subject: Re: [PATCH net-next 5/9] devlink: remove the registration guarantee of references
Date: Fri, 6 Jan 2023 13:42:58 +0100 [thread overview]
Message-ID: <Y7gXUqI0WHDlO4WX@nanopsycho> (raw)
In-Reply-To: <20230106063402.485336-6-kuba@kernel.org>
Fri, Jan 06, 2023 at 07:33:58AM CET, kuba@kernel.org wrote:
>The objective of exposing the devlink instance locks to
>drivers was to let them use these locks to prevent user space
>from accessing the device before it's fully initialized.
>This is difficult because devlink_unregister() waits for all
>references to be released, meaning that devlink_unregister()
>can't itself be called under the instance lock.
>
>To avoid this issue devlink_register() was moved after subobject
>registration a while ago. Unfortunately the netdev paths get
>a hold of the devlink instances _before_ they are registered.
>Ideally netdev should wait for devlink init to finish (synchronizing
>on the instance lock). This can't work because we don't know if the
>instance will _ever_ be registered (in case of failures it may not).
>The other option of returning an error until devlink_register()
>is called is unappealing (user space would get a notification
>netdev exist but would have to wait arbitrary amount of time
>before accessing some of its attributes).
>
>Weaken the guarantees of the devlink references.
>
>Holding a reference will now only guarantee that the memory
>of the object is around. Another way of looking at it is that
>the reference now protects the object not its "registered" status.
>Use devlink instance lock to synchronize unregistration.
>
>This implies that releasing of the "main" reference of the devlink
>instance moves from devlink_unregister() to devlink_free().
>
>Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
>Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
next prev parent reply other threads:[~2023-01-06 12:43 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-06 6:33 [PATCH net-next 0/9] devlink: remove the wait-for-references on unregister Jakub Kicinski
2023-01-06 6:33 ` [PATCH net-next 1/9] devlink: bump the instance index directly when iterating Jakub Kicinski
2023-01-06 12:17 ` Jiri Pirko
2023-01-06 6:33 ` [PATCH net-next 2/9] devlink: update the code in netns move to latest helpers Jakub Kicinski
2023-01-06 6:33 ` [PATCH net-next 3/9] devlink: protect devlink->dev by the instance lock Jakub Kicinski
2023-01-06 12:18 ` Jiri Pirko
2023-01-06 6:33 ` [PATCH net-next 4/9] devlink: always check if the devlink instance is registered Jakub Kicinski
2023-01-06 12:41 ` Jiri Pirko
2023-01-06 17:03 ` Jacob Keller
2023-01-06 21:19 ` Jakub Kicinski
2023-01-07 9:05 ` Jiri Pirko
2023-01-06 6:33 ` [PATCH net-next 5/9] devlink: remove the registration guarantee of references Jakub Kicinski
2023-01-06 12:42 ` Jiri Pirko [this message]
2023-01-06 6:33 ` [PATCH net-next 6/9] devlink: don't require setting features before registration Jakub Kicinski
2023-01-06 12:43 ` Jiri Pirko
2023-01-06 6:34 ` [PATCH net-next 7/9] devlink: allow registering parameters after the instance Jakub Kicinski
2023-01-06 12:55 ` Jiri Pirko
2023-01-06 21:22 ` Jakub Kicinski
2023-01-07 9:20 ` Jiri Pirko
2023-01-10 0:21 ` Jacob Keller
2023-01-10 16:35 ` Jiri Pirko
2023-01-10 20:22 ` Jakub Kicinski
2023-01-11 9:32 ` Jiri Pirko
2023-01-11 16:45 ` Jakub Kicinski
2023-01-11 21:29 ` Jacob Keller
2023-01-12 7:07 ` Leon Romanovsky
2023-01-12 14:59 ` Jiri Pirko
2023-01-12 19:58 ` Leon Romanovsky
2023-01-13 7:50 ` Jiri Pirko
2023-01-15 8:35 ` Leon Romanovsky
2023-01-16 10:33 ` Jiri Pirko
2023-01-16 11:25 ` Leon Romanovsky
2023-01-12 19:20 ` Jakub Kicinski
2023-01-12 20:09 ` Leon Romanovsky
2023-01-12 22:44 ` Jacob Keller
2023-01-13 6:45 ` Leon Romanovsky
2023-01-13 7:53 ` Jiri Pirko
2023-01-11 13:21 ` Jiri Pirko
2023-01-06 6:34 ` [PATCH net-next 8/9] netdevsim: rename a label Jakub Kicinski
2023-01-06 12:56 ` Jiri Pirko
2023-01-06 6:34 ` [PATCH net-next 9/9] netdevsim: move devlink registration under the instance lock Jakub Kicinski
2023-01-06 15:49 ` Jiri Pirko
2023-01-06 13:10 ` [PATCH net-next 0/9] devlink: remove the wait-for-references on unregister patchwork-bot+netdevbpf
2023-01-06 15:49 ` Jiri Pirko
2023-01-06 17:06 ` Jacob Keller
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