lockdep splat due to klist iteration from atomic context in Intel IOMMU driver
From: Lennert Buytenhek
Date: Mon Aug 15 2022 - 08:13:46 EST
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@xxxxxxx>
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?
[ 32.283545] DMAR: DRHD: handling fault status reg 3
[ 32.288571] DMAR: [DMA Write NO_PASID] Request device [00:1a.0] fault addr 0x0 [fault reason 0x05] PTE Write access is not set
[ 32.288576] DMAR: Dump dmar0 table entries for IOVA 0x0
[ 32.288579] DMAR: root entry: 0x0000000127f42001
[ 32.288581] DMAR: context entry: hi 0x0000000000001502, low 0x000000012d8ab001
[ 32.288589]
[ 32.288590] ================================
[ 32.288591] WARNING: inconsistent lock state
[ 32.288593] 5.20.0-0.rc0.20220812git7ebfc85e2cd7.10.fc38.x86_64 #1 Not tainted
[ 32.288594] --------------------------------
[ 32.288595] inconsistent {HARDIRQ-ON-W} -> {IN-HARDIRQ-W} usage.
[ 32.288596] rngd/1006 [HC1[1]:SC0[0]:HE0:SE1] takes:
[ 32.288598] ff177021416f2d78 (&k->k_lock){?.+.}-{2:2}, at: klist_next+0x1b/0x160
[ 32.288610] {HARDIRQ-ON-W} state was registered at:
[ 32.288611] lock_acquire+0xce/0x2d0
[ 32.288617] _raw_spin_lock+0x33/0x80
[ 32.288625] klist_add_tail+0x46/0x80
[ 32.288627] bus_add_device+0xee/0x150
[ 32.288632] device_add+0x39d/0x9a0
[ 32.288634] add_memory_block+0x108/0x1d0
[ 32.288640] memory_dev_init+0xe1/0x117
[ 32.288648] driver_init+0x43/0x4d
[ 32.288651] kernel_init_freeable+0x1c2/0x2cc
[ 32.288657] kernel_init+0x16/0x140
[ 32.288663] ret_from_fork+0x1f/0x30
[ 32.406866] irq event stamp: 7812
[ 32.406867] hardirqs last enabled at (7811): [<ffffffff85000e86>] asm_sysvec_apic_timer_interrupt+0x16/0x20
[ 32.406873] hardirqs last disabled at (7812): [<ffffffff84f16894>] irqentry_enter+0x54/0x60
[ 32.406876] softirqs last enabled at (7794): [<ffffffff840ff669>] __irq_exit_rcu+0xf9/0x170
[ 32.406883] softirqs last disabled at (7787): [<ffffffff840ff669>] __irq_exit_rcu+0xf9/0x170
[ 32.406886]
[ 32.406886] other info that might help us debug this:
[ 32.406886] Possible unsafe locking scenario:
[ 32.406886]
[ 32.406887] CPU0
[ 32.406888] ----
[ 32.406888] lock(&k->k_lock);
[ 32.406889] <Interrupt>
[ 32.406890] lock(&k->k_lock);
[ 32.406891]
[ 32.406891] *** DEADLOCK ***
[ 32.406891]
[ 32.406892] no locks held by rngd/1006.
[ 32.406893]
[ 32.406893] stack backtrace:
[ 32.406894] CPU: 0 PID: 1006 Comm: rngd Not tainted 5.20.0-0.rc0.20220812git7ebfc85e2cd7.10.fc38.x86_64 #1
[ 32.406897] Hardware name: Intel Corporation Idaville/Unknown, BIOS SB_IDVH .001.001.000.000.008.00006.D-569F2C6B571C2177 Aug 11 2022
[ 32.406898] Call Trace:
[ 32.406900] <TASK>
[ 32.406901] dump_stack_lvl+0x5b/0x77
[ 32.406910] mark_lock.cold+0x48/0xe1
[ 32.406916] ? find_held_lock+0x32/0x90
[ 32.406924] __lock_acquire+0x948/0x1ef0
[ 32.406926] ? __lock_acquire+0x388/0x1ef0
[ 32.406929] lock_acquire+0xce/0x2d0
[ 32.406931] ? klist_next+0x1b/0x160
[ 32.406933] ? lock_is_held_type+0xe8/0x140
[ 32.406936] ? find_held_lock+0x32/0x90
[ 32.406939] ? sched_clock_cpu+0xb/0xc0
[ 32.406942] ? system_root_device_release+0x10/0x10
[ 32.406944] _raw_spin_lock_irqsave+0x4d/0xa0
[ 32.406947] ? klist_next+0x1b/0x160
[ 32.406949] klist_next+0x1b/0x160
[ 32.406951] ? pci_uevent_ers+0x80/0x80
[ 32.406956] bus_find_device+0x52/0xa0
[ 32.406959] pci_get_domain_bus_and_slot+0x70/0xf0
[ 32.406968] dmar_fault_dump_ptes+0xf5/0x28f
[ 32.406972] dmar_fault.cold+0xf2/0x1e6
[ 32.487869] __handle_irq_event_percpu+0x90/0x330
[ 32.497674] handle_irq_event+0x34/0x70
[ 32.497677] handle_edge_irq+0x9f/0x240
[ 32.497681] __common_interrupt+0x6e/0x150
[ 32.497686] common_interrupt+0x5c/0xd0
[ 32.509825] asm_common_interrupt+0x22/0x40
[ 32.509828] RIP: 0033:0x7facc2b09688
[ 32.644127] Code: 98 48 83 c0 40 48 8b 00 48 f7 d0 48 89 c1 48 8b 45 98 48 83 c0 48 48 8b 00 48 21 c1 48 8b 45 98 48 83 c0 38 48 31 ca 48 89 10 <48> 8b 45 98 48 83 c0 60 48 8b 10 48 8b 45 98 48 83 c0 68 480
[ 32.644129] RSP: 002b:00007facc1c80820 EFLAGS: 00000202
[ 32.644132] RAX: 000055b21df61db8 RBX: 00007facbc004c10 RCX: 04428d8038200044
[ 32.644133] RDX: 5e6e24505b76b92a RSI: 1968b00000000000 RDI: 000055b21df61d80
[ 32.644135] RBP: 00007facc1c80890 R08: 00007facbc004c10 R09: 0000000000000064
[ 32.644136] R10: 00007fffeddfa080 R11: 00000000000078d6 R12: 0000000000000000
[ 32.697491] R13: 000055b21d88e440 R14: 000055b21d8892e5 R15: 000055b21d88a058
[ 32.697496] </TASK>
[ 32.697521] DMAR: PTE not present at level 4