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Message-ID: <ZN4hCzTJ0DN6iBDU@shell.armlinux.org.uk> Date: Thu, 17 Aug 2023 14:30:51 +0100 From: "Russell King (Oracle)" <linux@...linux.org.uk> To: Denis Kirjanov <dkirjanov@...e.de> Cc: Daniel Golle <daniel@...rotopia.org>, Alexander Couzens <lynxis@...0.eu>, Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Matthias Brugger <matthias.bgg@...il.com>, AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org Subject: Re: [PATCH net-next] net: pcs: lynxi: fully reconfigure if link is down On Thu, Aug 17, 2023 at 04:13:44PM +0300, Denis Kirjanov wrote: > btw is it a thread-safe to check the mpcs->interface member? > I've quick checked and phylink_pcs_config can be invoked from different places > and the code below does the following assignment: > mpcs->interface = interface; pcs_config is called from: - phylink_change_inband_advert() while holding pl->state_mutex - phylink_major_config() phylink_major_config() is called from: - phylink_resolve() while holding pl->state_mutex - phylink_ethtool_ksettings_set() while holding pl->state_mutex - phylink_mac_initial_config() phylink_mac_initial_config() is called from: - phylink_resume() - phylink_start() In both cases, these are called without holding pl->state_mutex, so one may think that they could be unsafe. In both cases, however, pl->phylink_disable_state is non-zero. phylink_change_inband_advert() will check whether PHYLINK_DISABLE_STOPPED is set, and not proceed to call pcs_config() in that case. In the phylink_resume() case, userspace isn't running, so there can't be a call to phylink_change_inband_advert(). So, one can assume (as must be the case of course, we're fiddling with hardware) that pcs_config() will always be run without another thread also running it for the same hardware. Two over-lapping pcs_config() calls would lead to an indeterminant hardware state. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!
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