| Message ID | 20161025180858.GA22422@localhost.localdomain (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
On 10/25/2016 02:08 PM, Keith Busch wrote: > On Fri, Oct 21, 2016 at 08:14:43AM -0400, Prarit Bhargava wrote: >> We have seen this at Red Hat on various drivers: nouveau, ahci, and pcieport >> (so far). Google search for "unhandled irq 16" yields many results reporting >> similar behavior during shutdown indicating that this problem is widespread. >> I can cause this to happen on a "stable" system by adding a 3 second delay in >> pci_device_shutdown() which causes the number of spurious interrupts to exceed >> the 100000 limit and display the warning above. Also note that by adding the >> 3 second delay, NVIDIA devices with device ID 0x0FF* hit this problem 100% of >> the time. >> >> darcari noticed that removing the pci_intx_for_msi() call resulted in a >> stable system. After further discussions with Myron and Alex, Alex came up >> idea of keeping the intx disabled during shutdown implemented below. >> >> ----8<---- >> >> The following unhandled IRQ warning is seen during shutdown: >> >> irq 16: nobody cared (try booting with the "irqpoll" option) >> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.8.2-1.el7_UNSUPPORTED.x86_64 #1 >> Hardware name: Hewlett-Packard HP Z820 Workstation/158B, BIOS J63 v03.90 06/01/2016 >> 0000000000000000 ffff88041f803e70 ffffffff81333bd5 ffff88041cb78200 >> ffff88041cb7829c ffff88041f803e98 ffffffff810d9465 ffff88041cb78200 >> 0000000000000000 0000000000000028 ffff88041f803ed0 ffffffff810d97bf >> Call Trace: >> <IRQ> [<ffffffff81333bd5>] dump_stack+0x63/0x8e >> [<ffffffff810d9465>] __report_bad_irq+0x35/0xd0 >> [<ffffffff810d97bf>] note_interrupt+0x20f/0x260 >> [<ffffffff810d6b35>] handle_irq_event_percpu+0x45/0x60 >> [<ffffffff810d6b7c>] handle_irq_event+0x2c/0x50 >> [<ffffffff810da31a>] handle_fasteoi_irq+0x8a/0x150 >> [<ffffffff8102edfb>] handle_irq+0xab/0x130 >> [<ffffffff81082391>] ? _local_bh_enable+0x21/0x50 >> [<ffffffff817064ad>] do_IRQ+0x4d/0xd0 >> [<ffffffff81704502>] common_interrupt+0x82/0x82 >> <EOI> [<ffffffff815d0181>] ? cpuidle_enter_state+0xc1/0x280 >> [<ffffffff815d0174>] ? cpuidle_enter_state+0xb4/0x280 >> [<ffffffff815d0377>] cpuidle_enter+0x17/0x20 >> [<ffffffff810bf660>] cpu_startup_entry+0x220/0x3a0 >> [<ffffffff816f6da7>] rest_init+0x77/0x80 >> [<ffffffff81d8e147>] start_kernel+0x495/0x4a2 >> [<ffffffff81d8daa0>] ? set_init_arg+0x55/0x55 >> [<ffffffff81d8d120>] ? early_idt_handler_array+0x120/0x120 >> [<ffffffff81d8d5d6>] x86_64_start_reservations+0x2a/0x2c >> [<ffffffff81d8d715>] x86_64_start_kernel+0x13d/0x14c >> >> This occurs because the pci_msi_shutdown() and pci_msix_shutdown() functions >> enable the legacy intx interrupt even though the device and driver were not >> configured for legacy intx. >> >> This patch blocks the enabling of intx during system shutdown or reboot. > > > I am feeling a bit cautious to tie this behavior to the system_state. Is > there better criteria to know we shouldn't enable INTx after disabling > MSI/MSI-x? It sounds like we would never want to enable INTx if a driver > still has IRQ actions tied to the MSI/MSI-x. Does this alternate proposal > look okay? > > --- > diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c > index bfdd074..90a4e84 100644 > --- a/drivers/pci/msi.c > +++ b/drivers/pci/msi.c > @@ -357,19 +357,30 @@ void pci_write_msi_msg(unsigned int irq, struct msi_msg *msg) > } > EXPORT_SYMBOL_GPL(pci_write_msi_msg); > > +static bool msi_has_action(struct pci_dev *dev) > +{ > + struct msi_desc *entry; > + int i; > + > + for_each_pci_msi_entry(entry, dev) { > + if (entry->irq) { > + for (i = 0; i < entry->nvec_used; i++) > + if (irq_has_action(entry->irq + i)) > + return true; > + } > + } > + return false; > +} > + > static void free_msi_irqs(struct pci_dev *dev) > { > struct list_head *msi_list = dev_to_msi_list(&dev->dev); > struct msi_desc *entry, *tmp; > struct attribute **msi_attrs; > struct device_attribute *dev_attr; > - int i, count = 0; > - > - for_each_pci_msi_entry(entry, dev) > - if (entry->irq) > - for (i = 0; i < entry->nvec_used; i++) > - BUG_ON(irq_has_action(entry->irq + i)); > + int count = 0; > > + BUG_ON(msi_has_action(dev)); > pci_msi_teardown_msi_irqs(dev); > > list_for_each_entry_safe(entry, tmp, msi_list, list) { > @@ -910,7 +921,8 @@ void pci_msi_shutdown(struct pci_dev *dev) > desc = first_pci_msi_entry(dev); > > pci_msi_set_enable(dev, 0); > - pci_intx_for_msi(dev, 1); > + if (!msi_has_action(dev)) > + pci_intx_for_msi(dev, 1); When pci_disable_msi() is currently called the result is that device is switched back to intx and then the MSI IRQs are free'd. This patch would modify that behavior, and intx would not be reenabled when pci_disable_msix() was called during runtime. With the system_state patch we're only affecting shutdown, which is seen as less risky than doing https://patchwork.kernel.org/patch/5990701/ I still can't get around the idea that we're modifying device behaviour without verifying the driver supports the new behaviour. I think that is the wrong thing to do and think we should reconsider the patch in the above link. I'd much rather live with the risk of the patch in the link than dealing with kvm, runtime module unloads, etc. P. > dev->msi_enabled = 0; > > /* Return the device with MSI unmasked as initial states */ > @@ -1024,7 +1036,8 @@ void pci_msix_shutdown(struct pci_dev *dev) > } > > pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_ENABLE, 0); > - pci_intx_for_msi(dev, 1); > + if (!msi_has_action(dev)) > + pci_intx_for_msi(dev, 1); > dev->msix_enabled = 0; > pcibios_alloc_irq(dev); > } > -- > > -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Oct 25, 2016 at 03:08:54PM -0400, Prarit Bhargava wrote: > When pci_disable_msi() is currently called the result is that device is > switched back to intx and then the MSI IRQs are free'd. This patch would > modify that behavior, and intx would not be reenabled when pci_disable_msix() > was called during runtime. With the system_state patch we're only affecting > shutdown, which is seen as less risky than doing My proposal isn't really modifying exisiting behavior since if it does, the currently in place expectations are being violated: if anyone calls "pci_disable_msi" with actions on the irqs being disabled, they're already screwed since they will hit the BUG_ON in free_msi_irqs. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 10/25/2016 06:16 PM, Keith Busch wrote: > On Tue, Oct 25, 2016 at 03:08:54PM -0400, Prarit Bhargava wrote: >> When pci_disable_msi() is currently called the result is that device is >> switched back to intx and then the MSI IRQs are free'd. This patch would >> modify that behavior, and intx would not be reenabled when pci_disable_msix() >> was called during runtime. With the system_state patch we're only affecting >> shutdown, which is seen as less risky than doing > > My proposal isn't really modifying exisiting behavior since if it does, > the currently in place expectations are being violated: if anyone calls > "pci_disable_msi" with actions on the irqs being disabled, they're > already screwed since they will hit the BUG_ON in free_msi_irqs. I thought msi_has_action() would have returned 1 until free_msi_irqs() was called. Yes, your patch would work. I also want to add this interesting tidbit: I have noticed in the past that *many* systems no longer print the Restarting system. reboot: machine restart [and some also print an extra line of, "ACPI MEMORY or I/O RESET_REG"] messages at the end of boot. For a long time I had assumed that this was because the reboot was racing with printk somehow and that the system shutdown or rebooted before those lines made it "out" through the serial port. With the previously rejected patch from https://patchwork.kernel.org/patch/5990701/ the messages are output to the screen again (I'm not 100% sure on this but I think this is occurring for systems where the serial port or usb port is behind a pci device). This result lends more support to the idea that we're doing something wrong by blindly disabling msi/x interrupts when the driver doesn't support it. There are several ways of fixing this, and I'm not sure one is better than the other. It seems no matter what we do here there's risk of breaking something and I'm leaning towards fixing this by only calling the msi disable code when a shutdown function has been called. Bjorn, I'd like to hear what you think... P. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c index bfdd074..90a4e84 100644 --- a/drivers/pci/msi.c +++ b/drivers/pci/msi.c @@ -357,19 +357,30 @@ void pci_write_msi_msg(unsigned int irq, struct msi_msg *msg) } EXPORT_SYMBOL_GPL(pci_write_msi_msg); +static bool msi_has_action(struct pci_dev *dev) +{ + struct msi_desc *entry; + int i; + + for_each_pci_msi_entry(entry, dev) { + if (entry->irq) { + for (i = 0; i < entry->nvec_used; i++) + if (irq_has_action(entry->irq + i)) + return true; + } + } + return false; +} + static void free_msi_irqs(struct pci_dev *dev) { struct list_head *msi_list = dev_to_msi_list(&dev->dev); struct msi_desc *entry, *tmp; struct attribute **msi_attrs; struct device_attribute *dev_attr; - int i, count = 0; - - for_each_pci_msi_entry(entry, dev) - if (entry->irq) - for (i = 0; i < entry->nvec_used; i++) - BUG_ON(irq_has_action(entry->irq + i)); + int count = 0; + BUG_ON(msi_has_action(dev)); pci_msi_teardown_msi_irqs(dev); list_for_each_entry_safe(entry, tmp, msi_list, list) { @@ -910,7 +921,8 @@ void pci_msi_shutdown(struct pci_dev *dev) desc = first_pci_msi_entry(dev); pci_msi_set_enable(dev, 0); - pci_intx_for_msi(dev, 1); + if (!msi_has_action(dev)) + pci_intx_for_msi(dev, 1); dev->msi_enabled = 0; /* Return the device with MSI unmasked as initial states */ @@ -1024,7 +1036,8 @@ void pci_msix_shutdown(struct pci_dev *dev) } pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_ENABLE, 0); - pci_intx_for_msi(dev, 1); + if (!msi_has_action(dev)) + pci_intx_for_msi(dev, 1); dev->msix_enabled = 0; pcibios_alloc_irq(dev); }