This is a note to let you know that I've just added the patch titled PCI: pciehp: Use down_read/write_nested(reset_lock) to fix lockdep errors to the 5.16-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: pci-pciehp-use-down_read-write_nested-reset_lock-to-fix-lockdep-errors.patch and it can be found in the queue-5.16 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 085a9f43433f30cbe8a1ade62d9d7827c3217f4d Mon Sep 17 00:00:00 2001 From: Hans de Goede <hdegoede@xxxxxxxxxx> Date: Fri, 17 Dec 2021 15:17:09 +0100 Subject: PCI: pciehp: Use down_read/write_nested(reset_lock) to fix lockdep errors From: Hans de Goede <hdegoede@xxxxxxxxxx> commit 085a9f43433f30cbe8a1ade62d9d7827c3217f4d upstream. Use down_read_nested() and down_write_nested() when taking the ctrl->reset_lock rw-sem, passing the number of PCIe hotplug controllers in the path to the PCI root bus as lock subclass parameter. This fixes the following false-positive lockdep report when unplugging a Lenovo X1C8 from a Lenovo 2nd gen TB3 dock: pcieport 0000:06:01.0: pciehp: Slot(1): Link Down pcieport 0000:06:01.0: pciehp: Slot(1): Card not present ============================================ WARNING: possible recursive locking detected 5.16.0-rc2+ #621 Not tainted -------------------------------------------- irq/124-pciehp/86 is trying to acquire lock: ffff8e5ac4299ef8 (&ctrl->reset_lock){.+.+}-{3:3}, at: pciehp_check_presence+0x23/0x80 but task is already holding lock: ffff8e5ac4298af8 (&ctrl->reset_lock){.+.+}-{3:3}, at: pciehp_ist+0xf3/0x180 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&ctrl->reset_lock); lock(&ctrl->reset_lock); *** DEADLOCK *** May be due to missing lock nesting notation 3 locks held by irq/124-pciehp/86: #0: ffff8e5ac4298af8 (&ctrl->reset_lock){.+.+}-{3:3}, at: pciehp_ist+0xf3/0x180 #1: ffffffffa3b024e8 (pci_rescan_remove_lock){+.+.}-{3:3}, at: pciehp_unconfigure_device+0x31/0x110 #2: ffff8e5ac1ee2248 (&dev->mutex){....}-{3:3}, at: device_release_driver+0x1c/0x40 stack backtrace: CPU: 4 PID: 86 Comm: irq/124-pciehp Not tainted 5.16.0-rc2+ #621 Hardware name: LENOVO 20U90SIT19/20U90SIT19, BIOS N2WET30W (1.20 ) 08/26/2021 Call Trace: <TASK> dump_stack_lvl+0x59/0x73 __lock_acquire.cold+0xc5/0x2c6 lock_acquire+0xb5/0x2b0 down_read+0x3e/0x50 pciehp_check_presence+0x23/0x80 pciehp_runtime_resume+0x5c/0xa0 device_for_each_child+0x45/0x70 pcie_port_device_runtime_resume+0x20/0x30 pci_pm_runtime_resume+0xa7/0xc0 __rpm_callback+0x41/0x110 rpm_callback+0x59/0x70 rpm_resume+0x512/0x7b0 __pm_runtime_resume+0x4a/0x90 __device_release_driver+0x28/0x240 device_release_driver+0x26/0x40 pci_stop_bus_device+0x68/0x90 pci_stop_bus_device+0x2c/0x90 pci_stop_and_remove_bus_device+0xe/0x20 pciehp_unconfigure_device+0x6c/0x110 pciehp_disable_slot+0x5b/0xe0 pciehp_handle_presence_or_link_change+0xc3/0x2f0 pciehp_ist+0x179/0x180 This lockdep warning is triggered because with Thunderbolt, hotplug ports are nested. When removing multiple devices in a daisy-chain, each hotplug port's reset_lock may be acquired recursively. It's never the same lock, so the lockdep splat is a false positive. Because locks at the same hierarchy level are never acquired recursively, a per-level lockdep class is sufficient to fix the lockdep warning. The choice to use one lockdep subclass per pcie-hotplug controller in the path to the root-bus was made to conserve class keys because their number is limited and the complexity grows quadratically with number of keys according to Documentation/locking/lockdep-design.rst. Link: https://lore.kernel.org/linux-pci/20190402021933.GA2966@xxxxxxx/ Link: https://lore.kernel.org/linux-pci/de684a28-9038-8fc6-27ca-3f6f2f6400d7@xxxxxxxxxx/ Link: https://lore.kernel.org/r/20211217141709.379663-1-hdegoede@xxxxxxxxxx Link: https://bugzilla.kernel.org/show_bug.cgi?id=208855 Reported-by: "Theodore Ts'o" <tytso@xxxxxxx> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> Reviewed-by: Lukas Wunner <lukas@xxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/pci/hotplug/pciehp.h | 3 +++ drivers/pci/hotplug/pciehp_core.c | 2 +- drivers/pci/hotplug/pciehp_hpc.c | 21 ++++++++++++++++++--- 3 files changed, 22 insertions(+), 4 deletions(-) --- a/drivers/pci/hotplug/pciehp.h +++ b/drivers/pci/hotplug/pciehp.h @@ -75,6 +75,8 @@ extern int pciehp_poll_time; * @reset_lock: prevents access to the Data Link Layer Link Active bit in the * Link Status register and to the Presence Detect State bit in the Slot * Status register during a slot reset which may cause them to flap + * @depth: Number of additional hotplug ports in the path to the root bus, + * used as lock subclass for @reset_lock * @ist_running: flag to keep user request waiting while IRQ thread is running * @request_result: result of last user request submitted to the IRQ thread * @requester: wait queue to wake up on completion of user request, @@ -106,6 +108,7 @@ struct controller { struct hotplug_slot hotplug_slot; /* hotplug core interface */ struct rw_semaphore reset_lock; + unsigned int depth; unsigned int ist_running; int request_result; wait_queue_head_t requester; --- a/drivers/pci/hotplug/pciehp_core.c +++ b/drivers/pci/hotplug/pciehp_core.c @@ -166,7 +166,7 @@ static void pciehp_check_presence(struct { int occupied; - down_read(&ctrl->reset_lock); + down_read_nested(&ctrl->reset_lock, ctrl->depth); mutex_lock(&ctrl->state_lock); occupied = pciehp_card_present_or_link_active(ctrl); --- a/drivers/pci/hotplug/pciehp_hpc.c +++ b/drivers/pci/hotplug/pciehp_hpc.c @@ -583,7 +583,7 @@ static void pciehp_ignore_dpc_link_chang * the corresponding link change may have been ignored above. * Synthesize it to ensure that it is acted on. */ - down_read(&ctrl->reset_lock); + down_read_nested(&ctrl->reset_lock, ctrl->depth); if (!pciehp_check_link_active(ctrl)) pciehp_request(ctrl, PCI_EXP_SLTSTA_DLLSC); up_read(&ctrl->reset_lock); @@ -746,7 +746,7 @@ static irqreturn_t pciehp_ist(int irq, v * Disable requests have higher priority than Presence Detect Changed * or Data Link Layer State Changed events. */ - down_read(&ctrl->reset_lock); + down_read_nested(&ctrl->reset_lock, ctrl->depth); if (events & DISABLE_SLOT) pciehp_handle_disable_request(ctrl); else if (events & (PCI_EXP_SLTSTA_PDC | PCI_EXP_SLTSTA_DLLSC)) @@ -906,7 +906,7 @@ int pciehp_reset_slot(struct hotplug_slo if (probe) return 0; - down_write(&ctrl->reset_lock); + down_write_nested(&ctrl->reset_lock, ctrl->depth); if (!ATTN_BUTTN(ctrl)) { ctrl_mask |= PCI_EXP_SLTCTL_PDCE; @@ -962,6 +962,20 @@ static inline void dbg_ctrl(struct contr #define FLAG(x, y) (((x) & (y)) ? '+' : '-') +static inline int pcie_hotplug_depth(struct pci_dev *dev) +{ + struct pci_bus *bus = dev->bus; + int depth = 0; + + while (bus->parent) { + bus = bus->parent; + if (bus->self && bus->self->is_hotplug_bridge) + depth++; + } + + return depth; +} + struct controller *pcie_init(struct pcie_device *dev) { struct controller *ctrl; @@ -975,6 +989,7 @@ struct controller *pcie_init(struct pcie return NULL; ctrl->pcie = dev; + ctrl->depth = pcie_hotplug_depth(dev->port); pcie_capability_read_dword(pdev, PCI_EXP_SLTCAP, &slot_cap); if (pdev->hotplug_user_indicators) Patches currently in stable-queue which might be from hdegoede@xxxxxxxxxx are queue-5.16/media-atomisp-ov2680-fix-ov2680_set_fmt-clobbering-t.patch queue-5.16/acpi-battery-add-the-thinkpad-not-charging-quirk.patch queue-5.16/acpi-x86-allow-specifying-acpi_device_override_statu.patch queue-5.16/media-i2c-ov8865-fix-lockdep-error.patch queue-5.16/mfd-intel_soc_pmic-use-cpu-id-check-instead-of-_hrv-.patch queue-5.16/acpi-scan-create-platform-device-for-bcm4752-and-lnv.patch queue-5.16/platform-x86-wmi-replace-read_takes_no_args-with-a-f.patch queue-5.16/drm-panel-orientation-quirks-add-quirk-for-the-lenov.patch queue-5.16/gpiolib-acpi-do-not-set-the-irq-type-if-the-irq-is-a.patch queue-5.16/drm-vboxvideo-fix-a-null-vs-is_err-check.patch queue-5.16/platform-x86-wmi-fix-driver-notify-vs-probe-race.patch queue-5.16/acpi-x86-drop-pwm2-device-on-lenovo-yoga-book-from-a.patch queue-5.16/acpi-change-acpi_device_always_present-into-acpi_dev.patch queue-5.16/pci-pciehp-use-down_read-write_nested-reset_lock-to-fix-lockdep-errors.patch queue-5.16/acpi-x86-add-not-present-quirk-for-the-pci0.sdhb.brc.patch