Messages in this thread | | | Date | Wed, 17 Aug 2022 12:45:26 +0800 | Subject | Re: lockdep splat due to klist iteration from atomic context in Intel IOMMU driver | From | Baolu Lu <> |
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On 2022/8/15 21:32, Bart Van Assche wrote: > On 8/15/22 05:05, Lennert Buytenhek wrote: >> On a build of 7ebfc85e2cd7 ("Merge tag 'net-6.0-rc1' of >> git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net"), with >> CONFIG_INTEL_IOMMU_DEBUGFS enabled, I am seeing the lockdep splat >> below when an I/O page fault occurs on a machine with an Intel >> IOMMU in it. >> >> The issue seems to be the klist iterator functions using >> spin_*lock_irq*() but the klist insertion functions using >> spin_*lock(), combined with the Intel DMAR IOMMU driver iterating >> over klists from atomic (hardirq) context as of commit 8ac0b64b9735 >> ("iommu/vt-d: Use pci_get_domain_bus_and_slot() in pgtable_walk()") >> when CONFIG_INTEL_IOMMU_DEBUGFS is enabled, where >> pci_get_domain_bus_and_slot() calls into bus_find_device() which >> iterates over klists. >> >> I found this commit from 2018: >> >> commit 624fa7790f80575a4ec28fbdb2034097dc18d051 >> Author: Bart Van Assche <bvanassche@acm.org> >> Date: Fri Jun 22 14:54:49 2018 -0700 >> >> scsi: klist: Make it safe to use klists in atomic context >> >> This commit switched lib/klist.c:klist_{prev,next} from >> spin_{,un}lock() to spin_{lock_irqsave,unlock_irqrestore}(), but left >> the spin_{,un}lock() calls in add_{head,tail}() untouched. >> >> The simplest fix for this would be to switch >> lib/klist.c:add_{head,tail}() >> over to use the IRQ-safe spinlock variants as well? > > Another possibility would be to evaluate whether it is safe to revert > commit 624fa7790f80 ("scsi: klist: Make it safe to use klists in atomic > context"). That commit is no longer needed by the SRP transport driver > since the legacy block layer has been removed from the kernel.
If so, pci_get_domain_bus_and_slot() can not be used in this interrupt context, right?
Best regards, baolu
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