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SubjectRe: [PATCH v2] PCI/LINK: bw_notification: Do not leave interrupt handler NULL
On Mon, 25 Mar 2019 17:25:02 -0500
Bjorn Helgaas <helgaas@kernel.org> wrote:

> On Fri, Mar 22, 2019 at 07:36:51PM -0500, Alexandru Gagniuc wrote:
> > A threaded IRQ with a NULL handler does not work with level-triggered
> > interrupts. request_threaded_irq() will return an error:
> >
> > genirq: Threaded irq requested with handler=NULL and !ONESHOT for irq 16
> > pcie_bw_notification: probe of 0000:00:1b.0:pcie010 failed with error -22
> >
> > For level interrupts we need to silence the interrupt before exiting
> > the IRQ handler, so just clear the PCI_EXP_LNKSTA_LBMS bit there.
> >
> > Fixes: e8303bb7a75c ("PCI/LINK: Report degraded links via link bandwidth notification")
> > Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
> > Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
>
> Applied with the following subject line to for-linus for v5.1, thanks!
>
> PCI/LINK: Supply IRQ handler so level-triggered IRQs are acked

That made it a little tricky to track down this thread. I get a
regression bisected back to this when trying to do vfio device
assignment. I haven't dug further than the bisection, but I assume bus
resets are triggering this link bandwidth notifier code and nobody
thinks it's their interrupt:

[ 119.910738] irq 16: nobody cared (try booting with the "irqpoll" option)
[ 119.917455] CPU: 18 PID: 0 Comm: swapper/18 Not tainted 5.1.0-rc1+ #29
[ 119.923998] Hardware name: Hewlett-Packard HP Z820 Workstation/158B, BIOS J63 v03.69 03/25/2014
[ 119.932715] Call Trace:
[ 119.935169] <IRQ>
[ 119.937200] dump_stack+0x46/0x60
[ 119.940534] __report_bad_irq+0x37/0xae
[ 119.944380] note_interrupt.cold.9+0xa/0x69
[ 119.948580] handle_irq_event_percpu+0x6a/0x80
[ 119.953037] handle_irq_event+0x3d/0x5a
[ 119.956887] handle_fasteoi_irq+0x8b/0x140
[ 119.961003] handle_irq+0xbf/0x100
[ 119.964420] do_IRQ+0x49/0xd0
[ 119.967398] common_interrupt+0xf/0xf
[ 119.971074] </IRQ>
[ 119.973190] RIP: 0010:cpuidle_enter_state+0xb4/0x460
[ 119.978167] Code: 24 0f 1f 44 00 00 31 ff e8 69 bf a3 ff 80 7c 24 13 00 74 12 9c 58 f6 c4 02 0f 85 7d 03 00 00 31 ff e8 60 cf a9 ff fb 45 85 e4 <0f> 88 ae 02 00 00 49 63 cc 4c 8b 3c 24 4c 2b 7c 24 08 48 8d 04 49
[ 119.996967] RSP: 0018:ffffb6740330fe98 EFLAGS: 00000202 ORIG_RAX: ffffffffffffffda
[ 120.004549] RAX: ffff9dbfc19a1d80 RBX: ffffffff82d2c940 RCX: 000000000000001f
[ 120.011700] RDX: 0000001beb3c9b05 RSI: 00000000315975dc RDI: 0000000000000000
[ 120.018845] RBP: ffff9dbfc19acc00 R08: 0000000000000002 R09: 0000000000021640
[ 120.025990] R10: 0000027ae2689456 R11: ffff9dbfc19a0e64 R12: 0000000000000004
[ 120.033146] R13: ffffffff82d2cad8 R14: 0000000000000004 R15: 0000000000000000
[ 120.040303] ? cpuidle_enter_state+0x97/0x460
[ 120.044679] do_idle+0x1f1/0x230
[ 120.047918] cpu_startup_entry+0x19/0x20
[ 120.051856] start_secondary+0x172/0x1c0
[ 120.055796] secondary_startup_64+0xb6/0xc0
[ 120.059993] handlers:
[ 120.062283] [<0000000054c59383>] usb_hcd_irq
[ 120.066563] Disabling IRQ #16
[ 122.885627] irq 16: nobody cared (try booting with the "irqpoll" option)
[ 122.892326] CPU: 18 PID: 0 Comm: swapper/18 Not tainted 5.1.0-rc1+ #29
[ 122.898847] Hardware name: Hewlett-Packard HP Z820 Workstation/158B, BIOS J63 v03.69 03/25/2014
[ 122.907532] Call Trace:
[ 122.909985] <IRQ>
[ 122.912009] dump_stack+0x46/0x60
[ 122.915325] __report_bad_irq+0x37/0xae
[ 122.919159] note_interrupt.cold.9+0xa/0x69
[ 122.923338] handle_irq_event_percpu+0x6a/0x80
[ 122.927781] handle_irq_event+0x3d/0x5a
[ 122.931630] handle_fasteoi_irq+0x8b/0x140
[ 122.935730] handle_irq+0xbf/0x100
[ 122.939137] do_IRQ+0x49/0xd0
[ 122.942108] common_interrupt+0xf/0xf
[ 122.945772] </IRQ>
[ 122.947881] RIP: 0010:cpuidle_enter_state+0xb4/0x460
[ 122.952845] Code: 24 0f 1f 44 00 00 31 ff e8 69 bf a3 ff 80 7c 24 13 00 74 12 9c 58 f6 c4 02 0f 85 7d 03 00 00 31 ff e8 60 cf a9 ff fb 45 85 e4 <0f> 88 ae 02 00 00 49 63 cc 4c 8b 3c 24 4c 2b 7c 24 08 48 8d 04 49
[ 122.971629] RSP: 0018:ffffb6740330fe98 EFLAGS: 00000202 ORIG_RAX: ffffffffffffffda
[ 122.979212] RAX: ffff9dbfc19a1d80 RBX: ffffffff82d2c940 RCX: 000000000000001f
[ 122.986361] RDX: 0000001c9c8daa6e RSI: 00000000315975dc RDI: 0000000000000000
[ 122.993517] RBP: ffff9dbfc19acc00 R08: 0000000000000002 R09: 0000000000021640
[ 123.000655] R10: 0000027cae52b176 R11: ffff9dbfc19a0e64 R12: 0000000000000004
[ 123.007777] R13: ffffffff82d2cad8 R14: 0000000000000004 R15: 0000000000000000
[ 123.014906] ? cpuidle_enter_state+0x97/0x460
[ 123.019270] do_idle+0x1f1/0x230
[ 123.022502] cpu_startup_entry+0x19/0x20
[ 123.026426] start_secondary+0x172/0x1c0
[ 123.030352] secondary_startup_64+0xb6/0xc0
[ 123.034536] handlers:
[ 123.036821] [<0000000054c59383>] usb_hcd_irq
[ 123.041106] [<000000006da712f0>] vfio_intx_handler [vfio_pci]
[ 123.046847] [<000000006da712f0>] vfio_intx_handler [vfio_pci]
[ 123.052592] [<000000006da712f0>] vfio_intx_handler [vfio_pci]
[ 123.058336] [<000000006da712f0>] vfio_intx_handler [vfio_pci]
[ 123.064090] [<000000006da712f0>] vfio_intx_handler [vfio_pci]
[ 123.069843] Disabling IRQ #16

Thanks,
Alex

> > ---
> > Changes since v1:
> > - move pcie_update_link_speed() to irq to prevent duplicate read of link_status
> > - Add Fixes: to commit message
> >
> > drivers/pci/pcie/bw_notification.c | 19 ++++++++++++++-----
> > 1 file changed, 14 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/pci/pcie/bw_notification.c b/drivers/pci/pcie/bw_notification.c
> > index d2eae3b7cc0f..c48746f1cf3c 100644
> > --- a/drivers/pci/pcie/bw_notification.c
> > +++ b/drivers/pci/pcie/bw_notification.c
> > @@ -44,11 +44,10 @@ static void pcie_disable_link_bandwidth_notification(struct pci_dev *dev)
> > pcie_capability_write_word(dev, PCI_EXP_LNKCTL, lnk_ctl);
> > }
> >
> > -static irqreturn_t pcie_bw_notification_handler(int irq, void *context)
> > +static irqreturn_t pcie_bw_notification_irq(int irq, void *context)
> > {
> > struct pcie_device *srv = context;
> > struct pci_dev *port = srv->port;
> > - struct pci_dev *dev;
> > u16 link_status, events;
> > int ret;
> >
> > @@ -58,6 +57,17 @@ static irqreturn_t pcie_bw_notification_handler(int irq, void *context)
> > if (ret != PCIBIOS_SUCCESSFUL || !events)
> > return IRQ_NONE;
> >
> > + pcie_capability_write_word(port, PCI_EXP_LNKSTA, events);
> > + pcie_update_link_speed(port->subordinate, link_status);
> > + return IRQ_WAKE_THREAD;
> > +}
> > +
> > +static irqreturn_t pcie_bw_notification_handler(int irq, void *context)
> > +{
> > + struct pcie_device *srv = context;
> > + struct pci_dev *port = srv->port;
> > + struct pci_dev *dev;
> > +
> > /*
> > * Print status from downstream devices, not this root port or
> > * downstream switch port.
> > @@ -67,8 +77,6 @@ static irqreturn_t pcie_bw_notification_handler(int irq, void *context)
> > __pcie_print_link_status(dev, false);
> > up_read(&pci_bus_sem);
> >
> > - pcie_update_link_speed(port->subordinate, link_status);
> > - pcie_capability_write_word(port, PCI_EXP_LNKSTA, events);
> > return IRQ_HANDLED;
> > }
> >
> > @@ -80,7 +88,8 @@ static int pcie_bandwidth_notification_probe(struct pcie_device *srv)
> > if (!pcie_link_bandwidth_notification_supported(srv->port))
> > return -ENODEV;
> >
> > - ret = request_threaded_irq(srv->irq, NULL, pcie_bw_notification_handler,
> > + ret = request_threaded_irq(srv->irq, pcie_bw_notification_irq,
> > + pcie_bw_notification_handler,
> > IRQF_SHARED, "PCIe BW notif", srv);
> > if (ret)
> > return ret;
> > --
> > 2.19.2
> >

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