On Sun, Feb 17, 2019 at 07:55:24PM +0000, Russell King - ARM Linux admin wrote:
> On Sun, Feb 17, 2019 at 07:11:43PM +0100, Andrew Lunn wrote:
> > The following false positive lockdep splat has been observed.
> >
> > ======================================================
> > WARNING: possible circular locking dependency detected
> > 4.20.0+ #302 Not tainted
> > ------------------------------------------------------
> > systemd-udevd/160 is trying to acquire lock:
> > edea6080 (&chip->reg_lock){+.+.}, at: __setup_irq+0x640/0x704
> >
> > but task is already holding lock:
> > edff0340 (&desc->request_mutex){+.+.}, at: __setup_irq+0xa0/0x704
> >
> > which lock already depends on the new lock.
> >
> > the existing dependency chain (in reverse order) is:
> >
> > -> #1 (&desc->request_mutex){+.+.}:
> > mutex_lock_nested+0x1c/0x24
> > __setup_irq+0xa0/0x704
> > request_threaded_irq+0xd0/0x150
> > mv88e6xxx_probe+0x41c/0x694 [mv88e6xxx]
> > mdio_probe+0x2c/0x54
> > really_probe+0x200/0x2c4
> > driver_probe_device+0x5c/0x174
> > __driver_attach+0xd8/0xdc
> > bus_for_each_dev+0x58/0x7c
> > bus_add_driver+0xe4/0x1f0
> > driver_register+0x7c/0x110
> > mdio_driver_register+0x24/0x58
> > do_one_initcall+0x74/0x2e8
> > do_init_module+0x60/0x1d0
> > load_module+0x1968/0x1ff4
> > sys_finit_module+0x8c/0x98
> > ret_fast_syscall+0x0/0x28
> > 0xbedf2ae8
> >
> > -> #0 (&chip->reg_lock){+.+.}:
> > __mutex_lock+0x50/0x8b8
> > mutex_lock_nested+0x1c/0x24
> > __setup_irq+0x640/0x704
> > request_threaded_irq+0xd0/0x150
> > mv88e6xxx_g2_irq_setup+0xcc/0x1b4 [mv88e6xxx]
> > mv88e6xxx_probe+0x44c/0x694 [mv88e6xxx]
> > mdio_probe+0x2c/0x54
> > really_probe+0x200/0x2c4
> > driver_probe_device+0x5c/0x174
> > __driver_attach+0xd8/0xdc
> > bus_for_each_dev+0x58/0x7c
> > bus_add_driver+0xe4/0x1f0
> > driver_register+0x7c/0x110
> > mdio_driver_register+0x24/0x58
> > do_one_initcall+0x74/0x2e8
> > do_init_module+0x60/0x1d0
> > load_module+0x1968/0x1ff4
> > sys_finit_module+0x8c/0x98
> > ret_fast_syscall+0x0/0x28
> > 0xbedf2ae8
> >
> > other info that might help us debug this:
> >
> > Possible unsafe locking scenario:
> >
> > CPU0 CPU1
> > ---- ----
> > lock(&desc->request_mutex);
> > lock(&chip->reg_lock);
> > lock(&desc->request_mutex);
> > lock(&chip->reg_lock);
> >
> > &desc->request_mutex refer to two different mutex. #1 is the GPIO for
> > the chip interrupt. #2 is the chained interrupt between global 1 and
> > global 2.
> >
> > Add lockdep classes to the GPIO interrupt to avoid this.
> >
> > Reported-by: Russell King <rmk+ker...@armlinux.org.uk>
> > Signed-off-by: Andrew Lunn <and...@lunn.ch>
> > ---
> >
> > Hi Russell
> >
> > Does this fix it for you on Clearfog?
>
> Yes, that also fixes the problem, but I do think this is just papering
> over mv88e6xxx needlessly holding locks when it doesn't need to do so.
Hi Andrew,
Do we have a way forward for this issue?
Thanks.
>
> >
> > drivers/net/dsa/mv88e6xxx/chip.c | 8 ++++++++
> > 1 file changed, 8 insertions(+)
> >
> > diff --git a/drivers/net/dsa/mv88e6xxx/chip.c
> > b/drivers/net/dsa/mv88e6xxx/chip.c
> > index 32e7af5caa69..936d53a92144 100644
> > --- a/drivers/net/dsa/mv88e6xxx/chip.c
> > +++ b/drivers/net/dsa/mv88e6xxx/chip.c
> > @@ -442,12 +442,20 @@ static int mv88e6xxx_g1_irq_setup_common(struct
> > mv88e6xxx_chip *chip)
> >
> > static int mv88e6xxx_g1_irq_setup(struct mv88e6xxx_chip *chip)
> > {
> > + static struct lock_class_key lock_key;
> > + static struct lock_class_key request_key;
> > int err;
> >
> > err = mv88e6xxx_g1_irq_setup_common(chip);
> > if (err)
> > return err;
> >
> > + /* These lock classes tells lockdep that global 1 irqs are in
> > + * a different category than their parent GPIO, so it won't
> > + * report false recursion.
> > + */
> > + irq_set_lockdep_class(chip->irq, &lock_key, &request_key);
> > +
> > err = request_threaded_irq(chip->irq, NULL,
> > mv88e6xxx_g1_irq_thread_fn,
> > IRQF_ONESHOT | IRQF_SHARED,
> > --
> > 2.20.1
> >
> >
>
> --
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
> According to speedtest.net: 11.9Mbps down 500kbps up
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
According to speedtest.net: 11.9Mbps down 500kbps up
