Re: [PATCH v2] phy state machine: failsafe leave invalid RUNNING state

[David Miller <davem@davemloft.net>]

From: Zefir Kurtisi <zefir.kurtisi@neratec.com>
Date: Fri,  6 Jan 2017 12:14:48 +0100

> While in RUNNING state, phy_state_machine() checks for link changes by
> comparing phydev->link before and after calling phy_read_status().
> This works as long as it is guaranteed that phydev->link is never
> changed outside the phy_state_machine().
> 
> If in some setups this happens, it causes the state machine to miss
> a link loss and remain RUNNING despite phydev->link being 0.
> 
> This has been observed running a dsa setup with a process continuously
> polling the link states over ethtool each second (SNMPD RFC-1213
> agent). Disconnecting the link on a phy followed by a ETHTOOL_GSET
> causes dsa_slave_get_settings() / dsa_slave_get_link_ksettings() to
> call phy_read_status() and with that modify the link status - and
> with that bricking the phy state machine.
> 
> This patch adds a fail-safe check while in RUNNING, which causes to
> move to CHANGELINK when the link is gone and we are still RUNNING.
> 
> Signed-off-by: Zefir Kurtisi <zefir.kurtisi@neratec.com>

Patch applied, thanks.