netdev - Re: [PATCH net] devlink: Wait longer before warning about unset port type

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Date:   Fri, 10 Jan 2020 16:46:50 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     idosch@...sch.org
Cc:     netdev@...r.kernel.org, jiri@...lanox.com,
        jakub.kicinski@...ronome.com, dvyukov@...gle.com,
        alexve@...lanox.com, mlxsw@...lanox.com, idosch@...lanox.com
Subject: Re: [PATCH net] devlink: Wait longer before warning about unset
 port type

From: Ido Schimmel <idosch@...sch.org>
Date: Thu,  9 Jan 2020 19:57:41 +0200

> From: Ido Schimmel <idosch@...lanox.com>
> 
> The commit cited below causes devlink to emit a warning if a type was
> not set on a devlink port for longer than 30 seconds to "prevent
> misbehavior of drivers". This proved to be problematic when
> unregistering the backing netdev. The flow is always:
> 
> devlink_port_type_clear()	// schedules the warning
> unregister_netdev()		// blocking
> devlink_port_unregister()	// cancels the warning
> 
> The call to unregister_netdev() can block for long periods of time for
> various reasons: RTNL lock is contended, large amounts of configuration
> to unroll following dismantle of the netdev, etc. This results in
> devlink emitting a warning despite the driver behaving correctly.
> 
> In emulated environments (of future hardware) which are usually very
> slow, the warning can also be emitted during port creation as more than
> 30 seconds can pass between the time the devlink port is registered and
> when its type is set.
> 
> In addition, syzbot has hit this warning [1] 1974 times since 07/11/19
> without being able to produce a reproducer. Probably because
> reproduction depends on the load or other bugs (e.g., RTNL not being
> released).
> 
> To prevent bogus warnings, increase the timeout to 1 hour.
> 
> [1] https://syzkaller.appspot.com/bug?id=e99b59e9c024a666c9f7450dc162a4b74d09d9cb
> 
> Fixes: 136bf27fc0e9 ("devlink: add warning in case driver does not set port type")
> Signed-off-by: Ido Schimmel <idosch@...lanox.com>
> Reported-by: syzbot+b0a18ed7b08b735d2f41@...kaller.appspotmail.com
> Reported-by: Alex Veber <alexve@...lanox.com>
> Tested-by: Alex Veber <alexve@...lanox.com>
> Acked-by: Jiri Pirko <jiri@...lanox.com>

Applied and queued up for v5.3+ -stable, thanks.