Commit a9873711 authored by Zefir Kurtisi's avatar Zefir Kurtisi Committed by Greg Kroah-Hartman

phy state machine: failsafe leave invalid RUNNING state


[ Upstream commit 811a9191 ]

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: default avatarZefir Kurtisi <zefir.kurtisi@neratec.com>
Reviewed-by: default avatarFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent db01878c
......@@ -921,6 +921,15 @@ void phy_state_machine(struct work_struct *work)
if (old_link != phydev->link)
phydev->state = PHY_CHANGELINK;
}
/*
* Failsafe: check that nobody set phydev->link=0 between two
* poll cycles, otherwise we won't leave RUNNING state as long
* as link remains down.
*/
if (!phydev->link && phydev->state == PHY_RUNNING) {
phydev->state = PHY_CHANGELINK;
dev_err(&phydev->dev, "no link in PHY_RUNNING\n");
}
break;
case PHY_CHANGELINK:
err = phy_read_status(phydev);
......
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