[+ Alex, linux-pci, kvm] On Thu, Oct 2, 2014 at 4:11 AM, <bugzilla-daemon@xxxxxxxxxxxxxxxxxxx> wrote: > https://bugzilla.kernel.org/show_bug.cgi?id=85441 > > Bug ID: 85441 > Summary: [vfio] [lockdep] Deadlock when attempting to unbind > device from a running VM > Product: Drivers > Version: 2.5 > Kernel Version: 3.17.0-rc7 and Ubuntu 3.13.0-36-generic > Hardware: x86-64 > OS: Linux > Tree: Mainline > Status: NEW > Severity: normal > Priority: P1 > Component: PCI > Assignee: drivers_pci@xxxxxxxxxxxxxxxxxxxx > Reporter: marti@xxxxxxxxx > Regression: No > > In order to assign a PCI device to a guest VM (using QEMU), we have a Python > script that unbinds all devices in the same IOMMU group and binds them to > pci-stub. > > When I run this script while the VM is running, it will hang forever, waiting > for this lock to be freed (causing a "task python3:xxxx blocked for more than > 120 seconds" error). Instead, it should probably fail immediately if the device > cannot be freed. > > Then, when I restart the Windows VM using this PCI device, while Python is > hanging, it causes the QEMU process to lock up as well -- this is in the 3.13 > kernel. > > I rebuilt the 3.13 Ubuntu kernel using LOCKDEP, but relevant locks appear to be > using __lockdep_no_validate__. Here are the hung task reports: > > ====================================================== > INFO: task qemu-system-x86:2828 blocked for more than 120 seconds. > Tainted: G X 3.13.11.7 #1 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > qemu-system-x86 D ffffffff81c154c0 0 2828 1 0x00000000 > ffff88039aa81d50 0000000000000046 ffff880411194240 ffff88039aa81fd8 > 00000000000150c0 00000000000150c0 ffff880411194240 ffff880429100000 > ffff8804291000f8 ffff880429100100 0000000000000246 ffff880411194240 > Call Trace: > [<ffffffff81734439>] schedule_preempt_disabled+0x29/0x70 > [<ffffffff8173715d>] mutex_lock_nested+0x16d/0x4b0 > [<ffffffff813c4c41>] ? pci_reset_function+0x51/0xa0 > [<ffffffff813c4c41>] pci_reset_function+0x51/0xa0 > [<ffffffffa0140c70>] vfio_pci_ioctl+0xf0/0xa40 [vfio_pci] > [<ffffffff810b53ef>] ? up_read+0x1f/0x40 > [<ffffffff8173dd04>] ? __do_page_fault+0x214/0x580 > [<ffffffff817393ac>] ? _raw_spin_unlock_irq+0x2c/0x40 > [<ffffffffa01291a3>] vfio_device_fops_unl_ioctl+0x23/0x30 [vfio] > [<ffffffff811e3b00>] do_vfs_ioctl+0x300/0x520 > [<ffffffff811eee9a>] ? fget_light+0xca/0x140 > [<ffffffff811e3da1>] SyS_ioctl+0x81/0xa0 > [<ffffffff8174282d>] system_call_fastpath+0x1a/0x1f > 1 lock held by qemu-system-x86/2828: > #0: (&__lockdep_no_validate__){......}, at: [<ffffffff813c4c41>] > pci_reset_function+0x51/0xa0 > INFO: task python3:3206 blocked for more than 120 seconds. > Tainted: G X 3.13.11.7 #1 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > python3 D ffff880429552120 0 3206 3205 0x00000000 > ffff88038d425d68 0000000000000046 ffff88038d69c240 ffff88038d425fd8 > 00000000000150c0 00000000000150c0 ffff88038d69c240 ffff88042961f400 > ffff880429100098 ffff88042370cc00 ffff8804285ff400 ffffffffffffffed > Call Trace: > [<ffffffff81733eb9>] schedule+0x29/0x70 > [<ffffffffa012a37a>] vfio_del_group_dev+0xaa/0x140 [vfio] > [<ffffffff810af3f0>] ? prepare_to_wait_event+0x100/0x100 > [<ffffffffa014010b>] vfio_pci_remove+0x1b/0x40 [vfio_pci] > [<ffffffff813c7a3b>] pci_device_remove+0x3b/0xb0 > [<ffffffff814b441f>] __device_release_driver+0x7f/0xf0 > [<ffffffff814b44b5>] device_release_driver+0x25/0x40 > [<ffffffff814b318f>] unbind_store+0xbf/0xe0 > [<ffffffff814b2584>] drv_attr_store+0x24/0x40 > [<ffffffff8124c3e9>] sysfs_write_file+0x179/0x1c0 > [<ffffffff811cfb54>] vfs_write+0xb4/0x1f0 > [<ffffffff811d0589>] SyS_write+0x49/0xa0 > [<ffffffff8174282d>] system_call_fastpath+0x1a/0x1f > 5 locks held by python3/3206: > #0: (sb_writers#5){.+.+.+}, at: [<ffffffff811cfc13>] vfs_write+0x173/0x1f0 > #1: (&of->mutex){+.+.+.}, at: [<ffffffff8124c36a>] > sysfs_write_file+0xfa/0x1c0 > #2: (s_active#3){++++.+}, at: [<ffffffff8124c372>] > sysfs_write_file+0x102/0x1c0 > #3: (&__lockdep_no_validate__){......}, at: [<ffffffff814b317f>] > unbind_store+0xaf/0xe0 > #4: (&__lockdep_no_validate__){......}, at: [<ffffffff814b44ad>] > device_release_driver+0x1d/0x40 > ====================================================== > > > I retried the same using kernel 3.17-rc7; the Python process messing with /sys > fs still hangs. I have not been able to reproduce the QEMU hang, but when I > tried, got the LOCKDEP error report below: > > ====================================================== > [ INFO: possible circular locking dependency detected ] > 3.17.0-rc7+ #2 Tainted: G E > ------------------------------------------------------- > python3/2563 is trying to acquire lock: > (&group->device_lock){+.+.+.}, at: [<ffffffffa0196ef4>] > vfio_group_get_device+0x24/0xb0 [vfio] > > but task is already holding lock: > (driver_lock){+.+.+.}, at: [<ffffffffa01d01cd>] vfio_pci_remove+0x1d/0x60 > [vfio_pci] > > which lock already depends on the new lock. > > > the existing dependency chain (in reverse order) is: > > -> #1 (driver_lock){+.+.+.}: > [<ffffffff810bc650>] lock_acquire+0xb0/0x140 > [<ffffffff817602e0>] mutex_lock_nested+0x50/0x4c0 > [<ffffffffa01d0618>] vfio_pci_open+0x38/0x270 [vfio_pci] > [<ffffffffa0197c35>] vfio_group_fops_unl_ioctl+0x265/0x490 [vfio] > [<ffffffff811fc160>] do_vfs_ioctl+0x300/0x520 > [<ffffffff811fc401>] SyS_ioctl+0x81/0xa0 > [<ffffffff817633ad>] system_call_fastpath+0x1a/0x1f > > -> #0 (&group->device_lock){+.+.+.}: > [<ffffffff810bc532>] __lock_acquire+0x1c22/0x1c90 > [<ffffffff810bc650>] lock_acquire+0xb0/0x140 > [<ffffffff817602e0>] mutex_lock_nested+0x50/0x4c0 > [<ffffffffa0196ef4>] vfio_group_get_device+0x24/0xb0 [vfio] > [<ffffffffa019737f>] vfio_del_group_dev+0x4f/0x140 [vfio] > [<ffffffffa01d01d9>] vfio_pci_remove+0x29/0x60 [vfio_pci] > [<ffffffff813d838b>] pci_device_remove+0x3b/0xb0 > [<ffffffff814c874f>] __device_release_driver+0x7f/0xf0 > [<ffffffff814c87e5>] device_release_driver+0x25/0x40 > [<ffffffff814c755f>] unbind_store+0xbf/0xe0 > [<ffffffff814c6924>] drv_attr_store+0x24/0x40 > [<ffffffff81263a44>] sysfs_kf_write+0x44/0x60 > [<ffffffff81263347>] kernfs_fop_write+0xe7/0x170 > [<ffffffff811e84c7>] vfs_write+0xb7/0x1f0 > [<ffffffff811e9079>] SyS_write+0x49/0xb0 > [<ffffffff817633ad>] system_call_fastpath+0x1a/0x1f > > other info that might help us debug this: > > Possible unsafe locking scenario: > > CPU0 CPU1 > ---- ---- > lock(driver_lock); > lock(&group->device_lock); > lock(driver_lock); > lock(&group->device_lock); > > *** DEADLOCK *** > > 6 locks held by python3/2563: > #0: (sb_writers#5){.+.+.+}, at: [<ffffffff811e85c3>] vfs_write+0x1b3/0x1f0 > #1: (&of->mutex){+.+.+.}, at: [<ffffffff8126331b>] > kernfs_fop_write+0xbb/0x170 > #2: (s_active#3){++++.+}, at: [<ffffffff81263323>] > kernfs_fop_write+0xc3/0x170 > #3: (&dev->mutex){......}, at: [<ffffffff814c754f>] unbind_store+0xaf/0xe0 > #4: (&dev->mutex){......}, at: [<ffffffff814c87dd>] > device_release_driver+0x1d/0x40 > #5: (driver_lock){+.+.+.}, at: [<ffffffffa01d01cd>] vfio_pci_remove+0x1d/0x60 > [vfio_pci] > > stack backtrace: > CPU: 1 PID: 2563 Comm: python3 Tainted: G E 3.17.0-rc7+ #2 > Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./FM2A88X Extreme6+, > BIOS P3.30 07/31/2014 > ffffffff826c0870 ffff88038fcdbb60 ffffffff8175971d ffffffff826c0870 > ffff88038fcdbba0 ffffffff817550e5 ffff88038fcdbbf0 ffff88040bdc4dc0 > 0000000000000005 ffff88040bdc4d98 ffff88040bdc4dc0 ffff88040bdc4440 > Call Trace: > [<ffffffff8175971d>] dump_stack+0x45/0x56 > [<ffffffff817550e5>] print_circular_bug+0x1f9/0x207 > [<ffffffff810bc532>] __lock_acquire+0x1c22/0x1c90 > [<ffffffff810b73ba>] ? __bfs+0x10a/0x220 > [<ffffffff810bc650>] lock_acquire+0xb0/0x140 > [<ffffffffa0196ef4>] ? vfio_group_get_device+0x24/0xb0 [vfio] > [<ffffffff817602e0>] mutex_lock_nested+0x50/0x4c0 > [<ffffffffa0196ef4>] ? vfio_group_get_device+0x24/0xb0 [vfio] > [<ffffffff810b96fa>] ? mark_held_locks+0x6a/0x90 > [<ffffffffa0196ef4>] vfio_group_get_device+0x24/0xb0 [vfio] > [<ffffffffa019737f>] vfio_del_group_dev+0x4f/0x140 [vfio] > [<ffffffff810b993d>] ? trace_hardirqs_on+0xd/0x10 > [<ffffffffa01d01d9>] vfio_pci_remove+0x29/0x60 [vfio_pci] > [<ffffffff813d838b>] pci_device_remove+0x3b/0xb0 > [<ffffffff814c874f>] __device_release_driver+0x7f/0xf0 > [<ffffffff814c87e5>] device_release_driver+0x25/0x40 > [<ffffffff814c755f>] unbind_store+0xbf/0xe0 > [<ffffffff814c6924>] drv_attr_store+0x24/0x40 > [<ffffffff81263a44>] sysfs_kf_write+0x44/0x60 > [<ffffffff81263347>] kernfs_fop_write+0xe7/0x170 > [<ffffffff811e84c7>] vfs_write+0xb7/0x1f0 > [<ffffffff811e9079>] SyS_write+0x49/0xb0 > [<ffffffff817633ad>] system_call_fastpath+0x1a/0x1f > ====================================================== > > -- > You are receiving this mail because: > You are watching the assignee of the bug. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
