Quoting Lu Baolu (2019-05-21 08:30:15) > From: Dave Jiang <dave.ji...@intel.com> > > Lockdep debug reported lock inversion related with the iommu code > caused by dmar_insert_one_dev_info() grabbing the iommu->lock and > the device_domain_lock out of order versus the code path in > iommu_flush_dev_iotlb(). Expanding the scope of the iommu->lock and > reversing the order of lock acquisition fixes the issue.
Which of course violates the property that device_domain_lock is the outer lock... <4>[ 1.252997] ====================================================== <4>[ 1.252999] WARNING: possible circular locking dependency detected <4>[ 1.253002] 5.2.0-rc5-CI-CI_DRM_6299+ #1 Not tainted <4>[ 1.253004] ------------------------------------------------------ <4>[ 1.253006] swapper/0/1 is trying to acquire lock: <4>[ 1.253009] 0000000091462475 (&(&iommu->lock)->rlock){+.+.}, at: domain_context_mapping_one+0xa0/0x4f0 <4>[ 1.253015] but task is already holding lock: <4>[ 1.253017] 0000000069266737 (device_domain_lock){....}, at: domain_context_mapping_one+0x88/0x4f0 <4>[ 1.253021] which lock already depends on the new lock. <4>[ 1.253024] the existing dependency chain (in reverse order) is: <4>[ 1.253027] -> #1 (device_domain_lock){....}: <4>[ 1.253031] _raw_spin_lock_irqsave+0x33/0x50 <4>[ 1.253034] dmar_insert_one_dev_info+0xb8/0x520 <4>[ 1.253036] set_domain_for_dev+0x66/0xf0 <4>[ 1.253039] iommu_prepare_identity_map+0x48/0x95 <4>[ 1.253042] intel_iommu_init+0xfd8/0x138d <4>[ 1.253045] pci_iommu_init+0x11/0x3a <4>[ 1.253048] do_one_initcall+0x58/0x300 <4>[ 1.253051] kernel_init_freeable+0x2c0/0x359 <4>[ 1.253054] kernel_init+0x5/0x100 <4>[ 1.253056] ret_from_fork+0x3a/0x50 <4>[ 1.253058] -> #0 (&(&iommu->lock)->rlock){+.+.}: <4>[ 1.253062] lock_acquire+0xa6/0x1c0 <4>[ 1.253064] _raw_spin_lock+0x2a/0x40 <4>[ 1.253067] domain_context_mapping_one+0xa0/0x4f0 <4>[ 1.253070] pci_for_each_dma_alias+0x2b/0x160 <4>[ 1.253072] dmar_insert_one_dev_info+0x44e/0x520 <4>[ 1.253075] set_domain_for_dev+0x66/0xf0 <4>[ 1.253077] iommu_prepare_identity_map+0x48/0x95 <4>[ 1.253080] intel_iommu_init+0xfd8/0x138d <4>[ 1.253082] pci_iommu_init+0x11/0x3a <4>[ 1.253084] do_one_initcall+0x58/0x300 <4>[ 1.253086] kernel_init_freeable+0x2c0/0x359 <4>[ 1.253089] kernel_init+0x5/0x100 <4>[ 1.253091] ret_from_fork+0x3a/0x50 <4>[ 1.253093] other info that might help us debug this: <4>[ 1.253095] Possible unsafe locking scenario: <4>[ 1.253095] CPU0 CPU1 <4>[ 1.253095] ---- ---- <4>[ 1.253095] lock(device_domain_lock); <4>[ 1.253095] lock(&(&iommu->lock)->rlock); <4>[ 1.253095] lock(device_domain_lock); <4>[ 1.253095] lock(&(&iommu->lock)->rlock); <4>[ 1.253095] *** DEADLOCK *** <4>[ 1.253095] 2 locks held by swapper/0/1: <4>[ 1.253095] #0: 0000000076465a1e (dmar_global_lock){++++}, at: intel_iommu_init+0x1d3/0x138d <4>[ 1.253095] #1: 0000000069266737 (device_domain_lock){....}, at: domain_context_mapping_one+0x88/0x4f0 <4>[ 1.253095] stack backtrace: <4>[ 1.253095] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.2.0-rc5-CI-CI_DRM_6299+ #1 <4>[ 1.253095] Hardware name: /NUC5i7RYB, BIOS RYBDWi35.86A.0362.2017.0118.0940 01/18/2017 <4>[ 1.253095] Call Trace: <4>[ 1.253095] dump_stack+0x67/0x9b <4>[ 1.253095] print_circular_bug+0x1c8/0x2b0 <4>[ 1.253095] __lock_acquire+0x1ce9/0x24c0 <4>[ 1.253095] ? lock_acquire+0xa6/0x1c0 <4>[ 1.253095] lock_acquire+0xa6/0x1c0 <4>[ 1.253095] ? domain_context_mapping_one+0xa0/0x4f0 <4>[ 1.253095] _raw_spin_lock+0x2a/0x40 <4>[ 1.253095] ? domain_context_mapping_one+0xa0/0x4f0 <4>[ 1.253095] domain_context_mapping_one+0xa0/0x4f0 <4>[ 1.253095] ? domain_context_mapping_one+0x4f0/0x4f0 <4>[ 1.253095] pci_for_each_dma_alias+0x2b/0x160 <4>[ 1.253095] dmar_insert_one_dev_info+0x44e/0x520 <4>[ 1.253095] set_domain_for_dev+0x66/0xf0 <4>[ 1.253095] iommu_prepare_identity_map+0x48/0x95 <4>[ 1.253095] intel_iommu_init+0xfd8/0x138d <4>[ 1.253095] ? set_debug_rodata+0xc/0xc <4>[ 1.253095] ? set_debug_rodata+0xc/0xc <4>[ 1.253095] ? e820__memblock_setup+0x5b/0x5b <4>[ 1.253095] ? pci_iommu_init+0x11/0x3a <4>[ 1.253095] ? set_debug_rodata+0xc/0xc <4>[ 1.253095] pci_iommu_init+0x11/0x3a <4>[ 1.253095] do_one_initcall+0x58/0x300 <4>[ 1.253095] kernel_init_freeable+0x2c0/0x359 <4>[ 1.253095] ? rest_init+0x250/0x250 <4>[ 1.253095] kernel_init+0x5/0x100 <4>[ 1.253095] ret_from_fork+0x3a/0x50