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Date: Tue, 13 Dec 2022 14:06:33 -0800 From: Alexander H Duyck <alexander.duyck@...il.com> To: "Hans J. Schultz" <netdev@...io-technology.com>, davem@...emloft.net, kuba@...nel.org Cc: netdev@...r.kernel.org, Andrew Lunn <andrew@...n.ch>, Florian Fainelli <f.fainelli@...il.com>, Vladimir Oltean <olteanv@...il.com>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, open list <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v2 net-next 2/3] net: dsa: mv88e6xxx: disable hold of chip lock for handling On Tue, 2022-12-13 at 18:46 +0100, Hans J. Schultz wrote: > As functions called under the interrupt handler will need to take the > netlink lock, we need to release the chip lock before calling those > functions as otherwise double lock deadlocks will occur as userspace > calls towards the driver often take the netlink lock and then the > chip lock. > > The deadlock would look like: > > Interrupt handler: chip lock taken, but cannot take netlink lock as > userspace config call has netlink lock. > Userspace config: netlink lock taken, but cannot take chip lock as > the interrupt handler has the chip lock. > > Signed-off-by: Hans J. Schultz <netdev@...io-technology.com> Just to confirm, in order to see the deadlocks I would imagine you need something in the tracepoints that is taking the netlink lock? If so you might want to reference the commit that switched out the dev_err_ratelimited for the tracepoints 8646384d80f3 ("net: dsa: mv88e6xxx: replace ATU violation prints with trace points") so that this patch can be found an applied to any kernels that pull in those tracepoints. > --- > drivers/net/dsa/mv88e6xxx/global1_atu.c | 14 ++++++++------ > 1 file changed, 8 insertions(+), 6 deletions(-) > > diff --git a/drivers/net/dsa/mv88e6xxx/global1_atu.c b/drivers/net/dsa/mv88e6xxx/global1_atu.c > index 61ae2d61e25c..34203e112eef 100644 > --- a/drivers/net/dsa/mv88e6xxx/global1_atu.c > +++ b/drivers/net/dsa/mv88e6xxx/global1_atu.c > @@ -409,11 +409,11 @@ static irqreturn_t mv88e6xxx_g1_atu_prob_irq_thread_fn(int irq, void *dev_id) > > err = mv88e6xxx_g1_read_atu_violation(chip); > if (err) > - goto out; > + goto out_unlock; > > err = mv88e6xxx_g1_read(chip, MV88E6XXX_G1_ATU_OP, &val); > if (err) > - goto out; > + goto out_unlock; > > err = mv88e6xxx_g1_atu_fid_read(chip, &fid); > if (err) > @@ -421,11 +421,13 @@ static irqreturn_t mv88e6xxx_g1_atu_prob_irq_thread_fn(int irq, void *dev_id) > > err = mv88e6xxx_g1_atu_data_read(chip, &entry); > if (err) > - goto out; > + goto out_unlock; > > err = mv88e6xxx_g1_atu_mac_read(chip, &entry); > if (err) > - goto out; > + goto out_unlock; > + > + mv88e6xxx_reg_unlock(chip); > > spid = entry.state; > > @@ -449,13 +451,13 @@ static irqreturn_t mv88e6xxx_g1_atu_prob_irq_thread_fn(int irq, void *dev_id) > fid); > chip->ports[spid].atu_full_violation++; > } > - mv88e6xxx_reg_unlock(chip); > > return IRQ_HANDLED; > > -out: > +out_unlock: > mv88e6xxx_reg_unlock(chip); > > +out: > dev_err(chip->dev, "ATU problem: error %d while handling interrupt\n", > err); > return IRQ_HANDLED; Reviewed-by: Alexander Duyck <alexanderduyck@...com>
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