Messages in this thread | | | Date | Tue, 07 Aug 2007 11:48:42 +0400 | From | "Denis V. Lunev" <> | Subject | Re: [PATCH] pci_get_device call from interrupt in reboot fixups |
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Andrew Morton wrote: > On Mon, 6 Aug 2007 19:49:10 -0700 Greg KH <gregkh@suse.de> wrote: > >> On Mon, Aug 06, 2007 at 11:16:20AM +0400, Denis V. Lunev wrote: >>> Greg KH wrote: >>>> On Fri, Aug 03, 2007 at 02:39:24PM +0400, Denis V. Lunev wrote: >>>>> The following calltrace is possible now: >>>>> handle_sysrq >>>>> machine_emergency_restart >>>>> mach_reboot_fixups >>>>> pci_get_device >>>>> pci_get_subsys >>>>> down_read >>>>> The patch obtains PCI device during initialization to avoid bothering PCI >>>>> search engine in interrupt. Devices used in this code are not supposed to >>>>> be pluggable, so it looks safe to keep them. >>>> What devices are supposed to be affected here? Are you sure that they >>>> can't be removed later? Grabbing references here might mess with them >>>> in the future. >>> Right now the list is the following: >>> static struct device_fixup fixups_table[] = { >>> { PCI_VENDOR_ID_CYRIX, PCI_DEVICE_ID_CYRIX_5530_LEGACY, >>> cs5530a_warm_reset }, >>> { PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_CS5536_ISA, cs5536_warm_reset }, >>> }; >>> >>> Though, if the approach is not suitable, we can skip fixups if we came >>> from sysrq. >> I don't think we really need to do fixups when we are "crashing" like >> this. The user really isn't shutting down the kernel as it should >> normally do. >> >> Andrew, I really don't want to change the PCI core to handle this, as we >> finally fixed a lot of issues with drivers trying to walk these lists >> from interrupt context. So if you want to just hide the warning message >> as we are shutting down, that's fine with me. Or just don't do the >> fixups. But grabbing a reference to the pci device is unsafe in my >> opinion and I do not want to do that. >> > > OK, good decision ;) > > One approach would be for some brave soul to pick his way through > the reboot code and ensure that we are correctly and reliably setting > system_state to SYSTEM_RESTART, then test that in __might_sleep(). > > But this does suppress somewhat-useful debugging just because of sysrq-B > and I really wouldn't want to utilise the horrid system_state any more that > we are presently doing. I think on balance that it would be better if we > could do something more targetted, like modify emergency_restart() to test > in_interrupt() and to then apologetically set some well-named global flag > which will shut up __might_sleep(). Pretty foul, but I can't think of > anything better.
__might_sleep prevention will solve the problem only partially :( There is a direct WARN_ON(in_interrupt()) in pci_get_subsys.
IMHO, calling down_read(&pci_bus_sem); from sysrq-B is not an option. I'll send a fixup disabling patch in a moment. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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