@@ -1034,13 +1034,6 @@ static int tb_switch_set_authorized(struct tb_switch *sw, unsigned int val)
if (sw->authorized)
goto unlock;
- /*
- * Make sure there is no PCIe rescan ongoing when a new PCIe
- * tunnel is created. Otherwise the PCIe rescan code might find
- * the new tunnel too early.
- */
- pci_lock_rescan_remove();
-
switch (val) {
/* Approve switch */
case 1:
@@ -1060,8 +1053,6 @@ static int tb_switch_set_authorized(struct tb_switch *sw, unsigned int val)
break;
}
- pci_unlock_rescan_remove();
-
if (!ret) {
sw->authorized = val;
/* Notify status change to the userspace */
When lockdep is enabled, plugging Thunderbolt dock on Dominik's laptop triggers following splat: ====================================================== WARNING: possible circular locking dependency detected 5.3.0-rc6+ #1 Tainted: G T ------------------------------------------------------ pool-/usr/lib/b/1258 is trying to acquire lock: 000000005ab0ad43 (pci_rescan_remove_lock){+.+.}, at: authorized_store+0xe8/0x210 but task is already holding lock: 00000000bfb796b5 (&tb->lock){+.+.}, at: authorized_store+0x7c/0x210 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&tb->lock){+.+.}: __mutex_lock+0xac/0x9a0 tb_domain_add+0x2d/0x130 nhi_probe+0x1dd/0x330 pci_device_probe+0xd2/0x150 really_probe+0xee/0x280 driver_probe_device+0x50/0xc0 bus_for_each_drv+0x84/0xd0 __device_attach+0xe4/0x150 pci_bus_add_device+0x4e/0x70 pci_bus_add_devices+0x2e/0x66 pci_bus_add_devices+0x59/0x66 pci_bus_add_devices+0x59/0x66 enable_slot+0x344/0x450 acpiphp_check_bridge.part.0+0x119/0x150 acpiphp_hotplug_notify+0xaa/0x140 acpi_device_hotplug+0xa2/0x3f0 acpi_hotplug_work_fn+0x1a/0x30 process_one_work+0x234/0x580 worker_thread+0x50/0x3b0 kthread+0x10a/0x140 ret_from_fork+0x3a/0x50 -> #0 (pci_rescan_remove_lock){+.+.}: __lock_acquire+0xe54/0x1ac0 lock_acquire+0xb8/0x1b0 __mutex_lock+0xac/0x9a0 authorized_store+0xe8/0x210 kernfs_fop_write+0x125/0x1b0 vfs_write+0xc2/0x1d0 ksys_write+0x6c/0xf0 do_syscall_64+0x50/0x180 entry_SYSCALL_64_after_hwframe+0x49/0xbe other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&tb->lock); lock(pci_rescan_remove_lock); lock(&tb->lock); lock(pci_rescan_remove_lock); *** DEADLOCK *** 5 locks held by pool-/usr/lib/b/1258: #0: 000000003df1a1ad (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x4d/0x60 #1: 0000000095a40b02 (sb_writers#6){.+.+}, at: vfs_write+0x185/0x1d0 #2: 0000000017a7d714 (&of->mutex){+.+.}, at: kernfs_fop_write+0xf2/0x1b0 #3: 000000004f262981 (kn->count#208){.+.+}, at: kernfs_fop_write+0xfa/0x1b0 #4: 00000000bfb796b5 (&tb->lock){+.+.}, at: authorized_store+0x7c/0x210 stack backtrace: CPU: 0 PID: 1258 Comm: pool-/usr/lib/b Tainted: G T 5.3.0-rc6+ #1 On an system using ACPI hotplug the host router gets hotplugged first and then the firmware starts sending notifications about connected devices so the above scenario should not happen in reality. However, after taking a second look at commit a03e828915c0 ("thunderbolt: Serialize PCIe tunnel creation with PCI rescan") that introduced the locking, I don't think it is actually correct. It may have cured the symptom but probably the real root cause was somewhere closer to PCI stack and possibly is already fixed with recent kernels. I also tried to reproduce the original issue with the commit reverted but could not. So to keep lockdep happy and the code bit less complex drop calls to pci_lock_rescan_remove()/pci_unlock_rescan_remove() in tb_switch_set_authorized() effectively reverting a03e828915c0. Link: https://lkml.org/lkml/2019/8/30/513 Fixes: a03e828915c0 ("thunderbolt: Serialize PCIe tunnel creation with PCI rescan") Reported-by: Dominik Brodowski <linux@dominikbrodowski.net> Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com> --- drivers/thunderbolt/switch.c | 9 --------- 1 file changed, 9 deletions(-)