On Sat, 31 Aug 2019 15:46:19 +0300, Vladimir Oltean <olte...@gmail.com> wrote:
> When a function such as dsa_slave_create fails, currently the following
> stack trace can be seen:
>
> [ 2.038342] sja1105 spi0.1: Probed switch chip: SJA1105T
> [ 2.054556] sja1105 spi0.1: Reset switch and programmed static config
> [ 2.063837] sja1105 spi0.1: Enabled switch tagging
> [ 2.068706] fsl-gianfar soc:ethernet@2d90000 eth2: error -19 setting up
> slave phy
> [ 2.076371] ------------[ cut here ]------------
> [ 2.080973] WARNING: CPU: 1 PID: 21 at net/core/devlink.c:6184
> devlink_free+0x1b4/0x1c0
> [ 2.088954] Modules linked in:
> [ 2.092005] CPU: 1 PID: 21 Comm: kworker/1:1 Not tainted
> 5.3.0-rc6-01360-g41b52e38d2b6-dirty #1746
> [ 2.100912] Hardware name: Freescale LS1021A
> [ 2.105162] Workqueue: events deferred_probe_work_func
> [ 2.110287] [<c03133a4>] (unwind_backtrace) from [<c030d8cc>]
> (show_stack+0x10/0x14)
> [ 2.117992] [<c030d8cc>] (show_stack) from [<c10b08d8>]
> (dump_stack+0xb4/0xc8)
> [ 2.125180] [<c10b08d8>] (dump_stack) from [<c0349d04>] (__warn+0xe0/0xf8)
> [ 2.132018] [<c0349d04>] (__warn) from [<c0349e34>]
> (warn_slowpath_null+0x40/0x48)
> [ 2.139549] [<c0349e34>] (warn_slowpath_null) from [<c0f19d74>]
> (devlink_free+0x1b4/0x1c0)
> [ 2.147772] [<c0f19d74>] (devlink_free) from [<c1064fc0>]
> (dsa_switch_teardown+0x60/0x6c)
> [ 2.155907] [<c1064fc0>] (dsa_switch_teardown) from [<c1065950>]
> (dsa_register_switch+0x8e4/0xaa8)
> [ 2.164821] [<c1065950>] (dsa_register_switch) from [<c0ba7fe4>]
> (sja1105_probe+0x21c/0x2ec)
> [ 2.173216] [<c0ba7fe4>] (sja1105_probe) from [<c0b35948>]
> (spi_drv_probe+0x80/0xa4)
> [ 2.180920] [<c0b35948>] (spi_drv_probe) from [<c0a4c1cc>]
> (really_probe+0x108/0x400)
> [ 2.188711] [<c0a4c1cc>] (really_probe) from [<c0a4c694>]
> (driver_probe_device+0x78/0x1bc)
> [ 2.196933] [<c0a4c694>] (driver_probe_device) from [<c0a4a3dc>]
> (bus_for_each_drv+0x58/0xb8)
> [ 2.205414] [<c0a4a3dc>] (bus_for_each_drv) from [<c0a4c024>]
> (__device_attach+0xd0/0x168)
> [ 2.213637] [<c0a4c024>] (__device_attach) from [<c0a4b1d0>]
> (bus_probe_device+0x84/0x8c)
> [ 2.221772] [<c0a4b1d0>] (bus_probe_device) from [<c0a4b72c>]
> (deferred_probe_work_func+0x84/0xc4)
> [ 2.230686] [<c0a4b72c>] (deferred_probe_work_func) from [<c03650a4>]
> (process_one_work+0x218/0x510)
> [ 2.239772] [<c03650a4>] (process_one_work) from [<c03660d8>]
> (worker_thread+0x2a8/0x5c0)
> [ 2.247908] [<c03660d8>] (worker_thread) from [<c036b348>]
> (kthread+0x148/0x150)
> [ 2.255265] [<c036b348>] (kthread) from [<c03010e8>]
> (ret_from_fork+0x14/0x2c)
> [ 2.262444] Exception stack(0xea965fb0 to 0xea965ff8)
> [ 2.267466] 5fa0: 00000000 00000000
> 00000000 00000000
> [ 2.275598] 5fc0: 00000000 00000000 00000000 00000000 00000000 00000000
> 00000000 00000000
> [ 2.283729] 5fe0: 00000000 00000000 00000000 00000000 00000013 00000000
> [ 2.290333] ---[ end trace ca5d506728a0581a ]---
>
> devlink_free is complaining right here:
>
> WARN_ON(!list_empty(&devlink->port_list));
>
> This happens because devlink_port_unregister is no longer done right
> away in dsa_port_setup when a DSA_PORT_TYPE_USER has failed.
> Vivien said about this change that:
>
> Also no need to call devlink_port_unregister from within dsa_port_setup
> as this step is inconditionally handled by dsa_port_teardown on error.
>
> which is not really true. The devlink_port_unregister function _is_
> being called unconditionally from within dsa_port_setup, but not for
> this port that just failed, just for the previous ones which were set
> up.
>
> ports_teardown:
> for (i = 0; i < port; i++)
> dsa_port_teardown(&ds->ports[i]);
>
> Initially I was tempted to fix this by extending the "for" loop to also
> cover the port that failed during setup. But this could have potentially
> unforeseen consequences unrelated to devlink_port or even other types of
> ports than user ports, which I can't really test for. For example, if
> for some reason devlink_port_register itself would fail, then
> unconditionally unregistering it in dsa_port_teardown would not be a
> smart idea. The list might go on.
>
> So just make dsa_port_setup undo the setup it had done upon failure, and
> let the for loop undo the work of setting up the previous ports, which
> are guaranteed to be brought up to a consistent state.
>
> Fixes: 955222ca5281 ("net: dsa: use a single switch statement for port setup")
> Signed-off-by: Vladimir Oltean <olte...@gmail.com>
Reviewed-by: Vivien Didelot <vivien.dide...@gmail.com>
This belongs to net-next. Thanks,
Vivien
