Hi,
When trying to rescan for PCI devices (after removing a child), I get a
lockdep warning in my logs. The commands were:
# tee /sys/bus/pci/devices/0000\:03\:00.0/remove <<<1
1
# tee /sys/bus/pci/devices/0000\:02\:00.0/rescan <<<1
1
I did not experience actual issues, just letting you know about this. I can
reproduce this on every reboot:
1. Boot
2. (pci-stub owns the device)
4. remove from parent bus
5. rescan
6. Lockdep warning found.
(7. pci-stub claims device again)
Interestingly, I can only reproduce this after freshly rebooting.
Repeating steps 4 and 5 do not trigger a new lockdep warning.
Regards,
Peter
======================================================
[ INFO: possible circular locking dependency detected ]
3.11.0-rc2-cold-00096-gae2ad35-dirty #1 Tainted: G O
-------------------------------------------------------
tee/29902 is trying to acquire lock:
(pci_remove_rescan_mutex){+.+.+.}, at: [<ffffffff8134be96>] dev_rescan_store+0x56/0x80
but task is already holding lock:
(s_active#296){++++.+}, at: [<ffffffff811fddad>] sysfs_write_file+0xcd/0x170
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (s_active#296){++++.+}:
[<ffffffff810aabaa>] check_prevs_add+0xda/0x140
[<ffffffff810ab1ba>] validate_chain.isra.35+0x5aa/0x7a0
[<ffffffff810ad02a>] __lock_acquire+0x3ca/0xab0
[<ffffffff810addc0>] lock_acquire+0x90/0x140
[<ffffffff811ff086>] sysfs_deactivate+0x116/0x160
[<ffffffff811ffb7b>] sysfs_addrm_finish+0x3b/0x70
[<ffffffff811fdb0b>] sysfs_hash_and_remove+0x5b/0xb0
[<ffffffff81201991>] remove_files.isra.1+0x41/0x80
[<ffffffff81201ec4>] sysfs_remove_group+0x54/0xf0
[<ffffffff8141415b>] device_remove_groups+0x3b/0x60
[<ffffffff814144a3>] device_remove_attrs+0x53/0x90
[<ffffffff81414e7b>] device_del+0x12b/0x1c0
[<ffffffff8134506c>] pci_stop_bus_device+0x9c/0xb0
[<ffffffff81345216>] pci_stop_and_remove_bus_device+0x16/0x30
[<ffffffff8134c10b>] remove_callback+0x2b/0x40
[<ffffffff811fde68>] sysfs_schedule_callback_work+0x18/0x80
[<ffffffff8106a621>] process_one_work+0x1d1/0x570
[<ffffffff8106b80b>] worker_thread+0x11b/0x370
[<ffffffff81072c2a>] kthread+0xea/0xf0
[<ffffffff8168239c>] ret_from_fork+0x7c/0xb0
-> #0 (pci_remove_rescan_mutex){+.+.+.}:
[<ffffffff810aaac8>] check_prev_add+0x778/0x780
[<ffffffff810aabaa>] check_prevs_add+0xda/0x140
[<ffffffff810ab1ba>] validate_chain.isra.35+0x5aa/0x7a0
[<ffffffff810ad02a>] __lock_acquire+0x3ca/0xab0
[<ffffffff810addc0>] lock_acquire+0x90/0x140
[<ffffffff816744a0>] mutex_lock_nested+0x70/0x380
[<ffffffff8134be96>] dev_rescan_store+0x56/0x80
[<ffffffff81413758>] dev_attr_store+0x18/0x30
[<ffffffff811fddc6>] sysfs_write_file+0xe6/0x170
[<ffffffff81187c5e>] vfs_write+0xce/0x200
[<ffffffff81188165>] SyS_write+0x55/0xa0
[<ffffffff81682442>] system_call_fastpath+0x16/0x1b
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(s_active#296);
lock(pci_remove_rescan_mutex);
lock(s_active#296);
lock(pci_remove_rescan_mutex);
*** DEADLOCK ***
3 locks held by tee/29902:
#0: (sb_writers#6){.+.+.+}, at: [<ffffffff81187d63>] vfs_write+0x1d3/0x200
#1: (&buffer->mutex){+.+.+.}, at: [<ffffffff811fdd24>] sysfs_write_file+0x44/0x170
#2: (s_active#296){++++.+}, at: [<ffffffff811fddad>] sysfs_write_file+0xcd/0x170
stack backtrace:
CPU: 2 PID: 29902 Comm: tee Tainted: G O 3.11.0-rc2-cold-00096-gae2ad35-dirty #1
Hardware name: Gigabyte Technology Co., Ltd. To be filled by O.E.M./Z68X-UD3H-B3, BIOS U1l 03/08/2013
ffff880597c7c6c8 ffff880544e69b28 ffffffff8166cea7 0000000000000000
0000000000000000 ffff880544e69b78 ffffffff81662c09 ffffffff821ac670
ffff880544e69ba0 ffff880544e69b78 ffff880597c7c6a0 ffff880597c7c6c8
Call Trace:
[<ffffffff8166cea7>] dump_stack+0x55/0x76
[<ffffffff81662c09>] print_circular_bug+0xd3/0xe4
[<ffffffff810aaac8>] check_prev_add+0x778/0x780
[<ffffffff8112f60e>] ? get_page_from_freelist+0x23e/0x5f0
[<ffffffff810aabaa>] check_prevs_add+0xda/0x140
[<ffffffff810ab1ba>] validate_chain.isra.35+0x5aa/0x7a0
[<ffffffff810ad02a>] __lock_acquire+0x3ca/0xab0
[<ffffffff81130092>] ? __alloc_pages_nodemask+0x162/0x980
[<ffffffff8134be96>] ? dev_rescan_store+0x56/0x80
[<ffffffff810addc0>] lock_acquire+0x90/0x140
[<ffffffff8134be96>] ? dev_rescan_store+0x56/0x80
[<ffffffff816744a0>] mutex_lock_nested+0x70/0x380
[<ffffffff8134be96>] ? dev_rescan_store+0x56/0x80
[<ffffffff811fddad>] ? sysfs_write_file+0xcd/0x170
[<ffffffff81329fac>] ? _kstrtoull+0x2c/0x90
[<ffffffff8134be96>] dev_rescan_store+0x56/0x80
[<ffffffff81413758>] dev_attr_store+0x18/0x30
[<ffffffff811fddc6>] sysfs_write_file+0xe6/0x170
[<ffffffff81187c5e>] vfs_write+0xce/0x200
[<ffffffff81188165>] SyS_write+0x55/0xa0
[<ffffffff81682442>] system_call_fastpath+0x16/0x1b
pci_bus 0000:02: scanning bus
pci 0000:02:00.0: scanning [bus 03-03] behind bridge, pass 0
pci_bus 0000:03: scanning bus
pci 0000:03:00.0: [10ec:8129] type 00 class 0x020000
pci 0000:03:00.0: reg 0x10: [io 0xe000-0xe0ff]
pci 0000:03:00.0: reg 0x14: [mem 0xf7b41000-0xf7b410ff]
pci 0000:03:00.0: reg 0x30: [mem 0xf7b00000-0xf7b3ffff pref]
pci 0000:03:00.0: PME# supported from D3cold
pci 0000:03:00.0: PME# disabled
pci_bus 0000:03: bus scan returning with max=03
pci 0000:02:00.0: scanning [bus 03-03] behind bridge, pass 1
pci_bus 0000:02: bus scan returning with max=03
pci 0000:02:00.0: BAR 15: assigned [mem 0xdfb00000-0xdfbfffff pref]
pci 0000:03:00.0: BAR 6: assigned [mem 0xdfb00000-0xdfb3ffff pref]
pci 0000:03:00.0: BAR 0: assigned [io 0xe000-0xe0ff]
pci 0000:03:00.0: BAR 0: set to [io 0xe000-0xe0ff] (PCI address [0xe000-0xe0ff])
pci 0000:03:00.0: BAR 1: assigned [mem 0xf7b00000-0xf7b000ff]
pci 0000:03:00.0: BAR 1: set to [mem 0xf7b00000-0xf7b000ff] (PCI address [0xf7b00000-0xf7b000ff])
pci-stub 0000:03:00.0: claimed by stub
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