| Message ID | 20240829161531.610874-4-maxime.chevallier@bootlin.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere, archived |
| Headers | show |
| Series | net: ethernet: fs_enet: Cleanup and phylink conversion | expand |
> --- a/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c > +++ b/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c > @@ -649,12 +649,7 @@ static void fs_adjust_link(struct net_device *dev) > unsigned long flags; > > spin_lock_irqsave(&fep->lock, flags); > - > - if (fep->ops->adjust_link) > - fep->ops->adjust_link(dev); > - else > - generic_adjust_link(dev); > - > + generic_adjust_link(dev); > spin_unlock_irqrestore(&fep->lock, flags); Holding a spinlock is pretty unusual. We are in thread context, and the phydev mutex is held. Looking at generic_adjust_link, do any of the fep->foo variables actually need protecting, particularly from changes in interrupts context? Andrew
Hi Andrew, On Fri, 30 Aug 2024 23:06:08 +0200 Andrew Lunn <andrew@lunn.ch> wrote: > > --- a/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c > > +++ b/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c > > @@ -649,12 +649,7 @@ static void fs_adjust_link(struct net_device *dev) > > unsigned long flags; > > > > spin_lock_irqsave(&fep->lock, flags); > > - > > - if (fep->ops->adjust_link) > > - fep->ops->adjust_link(dev); > > - else > > - generic_adjust_link(dev); > > - > > + generic_adjust_link(dev); > > spin_unlock_irqrestore(&fep->lock, flags); > > Holding a spinlock is pretty unusual. We are in thread context, and > the phydev mutex is held. Looking at generic_adjust_link, do any of > the fep->foo variables actually need protecting, particularly from > changes in interrupts context? Yes there are, the interrupt mask/event registers are being accessed from the interrupt handler and the ->restart() hook. I can try to rework this a bit for a cleaner interrupt handling, but I don't have means to test this on all mac flavors (fec/fcc/scc) :( Thanks for reviewing this, Maxime
On Wed, Sep 04, 2024 at 10:27:11AM +0200, Maxime Chevallier wrote: > Hi Andrew, > > On Fri, 30 Aug 2024 23:06:08 +0200 > Andrew Lunn <andrew@lunn.ch> wrote: > > > > --- a/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c > > > +++ b/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c > > > @@ -649,12 +649,7 @@ static void fs_adjust_link(struct net_device *dev) > > > unsigned long flags; > > > > > > spin_lock_irqsave(&fep->lock, flags); > > > - > > > - if (fep->ops->adjust_link) > > > - fep->ops->adjust_link(dev); > > > - else > > > - generic_adjust_link(dev); > > > - > > > + generic_adjust_link(dev); > > > spin_unlock_irqrestore(&fep->lock, flags); > > > > Holding a spinlock is pretty unusual. We are in thread context, and > > the phydev mutex is held. Looking at generic_adjust_link, do any of > > the fep->foo variables actually need protecting, particularly from > > changes in interrupts context? > > Yes there are, the interrupt mask/event registers are being accessed > from the interrupt handler and the ->restart() hook. I can try to > rework this a bit for a cleaner interrupt handling, but I don't have > means to test this on all mac flavors (fec/fcc/scc) :( As far as i can see, none of the fep->old* members are accessed outside of fs_enet-main.c. There values are not important for the restart call. So the spinlock has nothing to do with adjust_link as such, but restart. So maybe narrow down the lock to just the restart call? But it is not a big issues, just unusual. Andrew
On Wed, 4 Sep 2024 14:36:58 +0200 Andrew Lunn <andrew@lunn.ch> wrote: > On Wed, Sep 04, 2024 at 10:27:11AM +0200, Maxime Chevallier wrote: > > Hi Andrew, > > > > On Fri, 30 Aug 2024 23:06:08 +0200 > > Andrew Lunn <andrew@lunn.ch> wrote: > > > > > > --- a/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c > > > > +++ b/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c > > > > @@ -649,12 +649,7 @@ static void fs_adjust_link(struct net_device *dev) > > > > unsigned long flags; > > > > > > > > spin_lock_irqsave(&fep->lock, flags); > > > > - > > > > - if (fep->ops->adjust_link) > > > > - fep->ops->adjust_link(dev); > > > > - else > > > > - generic_adjust_link(dev); > > > > - > > > > + generic_adjust_link(dev); > > > > spin_unlock_irqrestore(&fep->lock, flags); > > > > > > Holding a spinlock is pretty unusual. We are in thread context, and > > > the phydev mutex is held. Looking at generic_adjust_link, do any of > > > the fep->foo variables actually need protecting, particularly from > > > changes in interrupts context? > > > > Yes there are, the interrupt mask/event registers are being accessed > > from the interrupt handler and the ->restart() hook. I can try to > > rework this a bit for a cleaner interrupt handling, but I don't have > > means to test this on all mac flavors (fec/fcc/scc) :( > > As far as i can see, none of the fep->old* members are accessed > outside of fs_enet-main.c. There values are not important for the > restart call. So the spinlock has nothing to do with adjust_link as > such, but restart. So maybe narrow down the lock to just the restart > call? But it is not a big issues, just unusual. I agree with you on that, and this is actually what end-up happening in the final phylink conversion patch (only the restart() call gets called wthin the spinlock). I'll however include a patch that does exactly what you suggest as part of the phylink conversion, both to make the big port-to-phylink patch smaller, but also to better document why we only need to care about the restart() part, if that's ok :) Thanks, Maxime
diff --git a/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c b/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c index 2b48a2a5e32d..caca81b3ccb6 100644 --- a/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c +++ b/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c @@ -649,12 +649,7 @@ static void fs_adjust_link(struct net_device *dev) unsigned long flags; spin_lock_irqsave(&fep->lock, flags); - - if (fep->ops->adjust_link) - fep->ops->adjust_link(dev); - else - generic_adjust_link(dev); - + generic_adjust_link(dev); spin_unlock_irqrestore(&fep->lock, flags); } diff --git a/drivers/net/ethernet/freescale/fs_enet/fs_enet.h b/drivers/net/ethernet/freescale/fs_enet/fs_enet.h index 21c07ac05225..abe4dc97e52a 100644 --- a/drivers/net/ethernet/freescale/fs_enet/fs_enet.h +++ b/drivers/net/ethernet/freescale/fs_enet/fs_enet.h @@ -77,7 +77,6 @@ struct fs_ops { void (*free_bd)(struct net_device *dev); void (*cleanup_data)(struct net_device *dev); void (*set_multicast_list)(struct net_device *dev); - void (*adjust_link)(struct net_device *dev); void (*restart)(struct net_device *dev); void (*stop)(struct net_device *dev); void (*napi_clear_event)(struct net_device *dev);