Subject: Re: [RFC PATCH net-next 04/11] atl1c: remove disable_irq from netpoll controller, use netpoll_irq_lock

From: Sabrina Dubroca <[email-masked]>
Date: Tue, 9 Dec 2014 18:23:10 +0100

2014-12-09, 16:13:33 +0000, Chris Snook wrote:
> Could you explain the bug a little more for us? It's not obvious to me how
> sleeping there is a problem.
> 
> -- Chris

Sorry for the lack of context.

A might_sleep() check in disable_irq() was added in commit
e22b886a8a43b ("sched/wait: Add might_sleep() checks") [1], and it
triggers when using netconsole:

BUG: sleeping function called from invalid context at kernel/irq/manage.c:104
in_atomic(): 1, irqs_disabled(): 1, pid: 1, name: systemd
no locks held by systemd/1.
irq event stamp: 10102965
hardirqs last  enabled at (10102965): [<ffffffff810cbafd>] vprintk_emit+0x2dd/0x6a0
hardirqs last disabled at (10102964): [<ffffffff810cb897>] vprintk_emit+0x77/0x6a0
softirqs last  enabled at (10102342): [<ffffffff810666aa>] __do_softirq+0x27a/0x6f0
softirqs last disabled at (10102337): [<ffffffff81066e86>] irq_exit+0x56/0xe0
Preemption disabled at:[<ffffffff817de50d>] printk_emit+0x31/0x33

CPU: 1 PID: 1 Comm: systemd Not tainted 3.18.0-rc2-next-20141029-dirty #222
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140617_173321-var-lib-archbuild-testing-x86_64-tobias 04/01/2014
 ffffffff81a82291 ffff88001e743978 ffffffff817df31d 0000000000000000
 0000000000000000 ffff88001e7439a8 ffffffff8108dfa2 ffff88001e7439a8
 ffffffff81a82291 0000000000000068 0000000000000000 ffff88001e7439d8
Call Trace:
 [<ffffffff817df31d>] dump_stack+0x4f/0x7c
 [<ffffffff8108dfa2>] ___might_sleep+0x182/0x2b0
 [<ffffffff8108e10a>] __might_sleep+0x3a/0xc0
 [<ffffffff810ce358>] synchronize_irq+0x38/0xa0
 [<ffffffff810ce633>] ? __disable_irq_nosync+0x43/0x70
 [<ffffffff810ce690>] disable_irq+0x20/0x30
 [<ffffffff815d7253>] e1000_netpoll+0x23/0x60
 [<ffffffff81678d02>] netpoll_poll_dev+0x72/0x3a0
 [<ffffffff817e9993>] ? _raw_spin_trylock+0x73/0x90
 [<ffffffff8167920f>] ? netpoll_send_skb_on_dev+0x1df/0x2e0
 [<ffffffff816791e7>] netpoll_send_skb_on_dev+0x1b7/0x2e0
 [<ffffffff816795f3>] netpoll_send_udp+0x2e3/0x490

The initial discussion of this problem is here: https://lkml.org/lkml/2014/10/29/523

[1] https://lkml.org/lkml/2014/10/28/427

> On Tue, Dec 9, 2014, 06:39 Sabrina Dubroca <[email-masked]> wrote:
> 
> > disable_irq() may sleep, replace it with a spin_lock in the interrupt
> > handler.
> >
> > No actual testing done, only compiled.
> >
> > Signed-off-by: Sabrina Dubroca <[email-masked]>
> > Cc: Jay Cliburn <[email-masked]>
> > Cc: Chris Snook <[email-masked]>
> > ---
> >  drivers/net/ethernet/atheros/atl1c/atl1c.h      |  3 +++
> >  drivers/net/ethernet/atheros/atl1c/atl1c_main.c | 12 ++++++++----
> >  2 files changed, 11 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/atheros/atl1c/atl1c.h
> > b/drivers/net/ethernet/atheros/atl1c/atl1c.h
> > index b9203d928938..8d97791e1516 100644
> > --- a/drivers/net/ethernet/atheros/atl1c/atl1c.h
> > +++ b/drivers/net/ethernet/atheros/atl1c/atl1c.h
> > @@ -49,6 +49,7 @@
> >  #include <linux/workqueue.h>
> >  #include <net/checksum.h>
> >  #include <net/ip6_checksum.h>
> > +#include <linux/netpoll.h>
> >
> >  #include "atl1c_hw.h"
> >
> > @@ -555,6 +556,8 @@ struct atl1c_adapter {
> >         struct atl1c_rfd_ring rfd_ring;
> >         struct atl1c_rrd_ring rrd_ring;
> >         u32 bd_number;     /* board number;*/
> > +
> > +       struct netpoll_irq_lock netpoll_lock;
> >  };
> >
> >  #define AT_WRITE_REG(a, reg, value) ( \
> > diff --git a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
> > b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
> > index 72fb86b9aa24..7a1b11eb8e4e 100644
> > --- a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
> > +++ b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
> > @@ -826,6 +826,7 @@ static int atl1c_sw_init(struct atl1c_adapter *adapter)
> >         atomic_set(&adapter->irq_sem, 1);
> >         spin_lock_init(&adapter->mdio_lock);
> >         spin_lock_init(&adapter->tx_lock);
> > +       netpoll_irq_lock_init(&adapter->netpoll_lock);
> >         set_bit(__AT_DOWN, &adapter->flags);
> >
> >         return 0;
> > @@ -1584,10 +1585,11 @@ static irqreturn_t atl1c_intr(int irq, void *data)
> >         struct pci_dev *pdev = adapter->pdev;
> >         struct atl1c_hw *hw = &adapter->hw;
> >         int max_ints = AT_MAX_INT_WORK;
> > -       int handled = IRQ_NONE;
> > +       irqreturn_t handled = IRQ_NONE;
> >         u32 status;
> >         u32 reg_data;
> >
> > +       netpoll_irq_lock(&adapter->netpoll_lock);
> >         do {
> >                 AT_READ_REG(hw, REG_ISR, &reg_data);
> >                 status = reg_data & hw->intr_mask;
> > @@ -1622,7 +1624,8 @@ static irqreturn_t atl1c_intr(int irq, void *data)
> >                         /* reset MAC */
> >                         set_bit(ATL1C_WORK_EVENT_RESET,
> > &adapter->work_event);
> >                         schedule_work(&adapter->common_task);
> > -                       return IRQ_HANDLED;
> > +                       handled = IRQ_HANDLED;
> > +                       goto out;
> >                 }
> >
> >                 if (status & ISR_OVER)
> > @@ -1641,6 +1644,9 @@ static irqreturn_t atl1c_intr(int irq, void *data)
> >         } while (--max_ints > 0);
> >         /* re-enable Interrupt*/
> >         AT_WRITE_REG(&adapter->hw, REG_ISR, 0);
> > +
> > +out:
> > +       netpoll_irq_unlock(&adapter->netpoll_lock);
> >         return handled;
> >  }
> >
> > @@ -1900,9 +1906,7 @@ static void atl1c_netpoll(struct net_device *netdev)
> >  {
> >         struct atl1c_adapter *adapter = netdev_priv(netdev);
> >
> > -       disable_irq(adapter->pdev->irq);
> >         atl1c_intr(adapter->pdev->irq, netdev);
> > -       enable_irq(adapter->pdev->irq);
> >  }
> >  #endif
> >
> > --
> > 2.1.3
> >
> >

-- 
Sabrina