Messages in this thread |  | | Date | Wed, 3 Sep 2025 16:52:09 +0100 | | From | "Russell King (Oracle)" <> | | Subject | Re: [PATCH v2 net 1/2] net: phylink: add lock for serializing concurrent pl->phydev writes with resolver |
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On Wed, Sep 03, 2025 at 06:31:20PM +0300, Vladimir Oltean wrote: > On Wed, Sep 03, 2025 at 04:26:35PM +0100, Russell King (Oracle) wrote: > > On Wed, Sep 03, 2025 at 06:23:47PM +0300, Vladimir Oltean wrote: > > > @@ -2305,6 +2314,7 @@ void phylink_disconnect_phy(struct phylink *pl) > > > > > > phy = pl->phydev; > > > if (phy) { > > > + mutex_lock(&pl->phy_lock); > > > > If we can, I think it would be better to place this a couple of lines > > above and move the unlock. > > Sorry for potentially misunderstanding, do you mean like this? > > mutex_lock(&pl->phy_lock); > phy = pl->phydev; > if (phy) { > mutex_lock(&phy->lock); > mutex_lock(&pl->state_mutex); > pl->phydev = NULL; > pl->phy_enable_tx_lpi = false; > pl->mac_tx_clk_stop = false; > mutex_unlock(&pl->state_mutex); > mutex_unlock(&phy->lock); > mutex_unlock(&pl->phy_lock); > flush_work(&pl->resolve); > > phy_disconnect(phy); > } else { > mutex_unlock(&pl->phy_lock); > } > > move the unlock where? because flush_work(&pl->resolve) needs to happen > unlocked, otherwise we'll deadlock with phylink_resolve(). > > Additionally, dereferincing pl->phydev under rtnl_lock() is already safe, > and doesn't need the secondary clock.
The reason I'm making the suggestion is for consistency. If the lock is there to ensure that reading pl->phydev is done safely, having one site where we read it and then take the lock makes it look confusing. I've also been thinking that it should be called pl->phydev_mutex (note that phylink uses _mutex for mutexes.)
To avoid it looking weird, what about this:
mutex_lock(&pl->phy_lock); phy = pl->phydev; if (phy) { mutex_lock(&phy->lock); mutex_lock(&pl->state_mutex); pl->phydev = NULL; pl->phy_enable_tx_lpi = false; pl->mac_tx_clk_stop = false; mutex_unlock(&pl->state_mutex); mutex_unlock(&phy->lock); } mutex_unlock(&pl->phy_lock);
if (phy) flush_work(&pl->resolve); phy_disconnect(phy); }
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