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authorHans de Goede <hdegoede@redhat.com>2021-12-17 15:17:09 +0100
committerBjorn Helgaas <bhelgaas@google.com>2022-01-12 06:42:51 -0600
commit085a9f43433f30cbe8a1ade62d9d7827c3217f4d (patch)
tree0475dbe8ab93214dbb61bc31affe5357056b4ccf /drivers/pci/hotplug
parente1a6333e7f89ad6acef9e818c2500c2e5393536e (diff)
downloadlinux-085a9f43433f30cbe8a1ade62d9d7827c3217f4d.tar.bz2
PCI: pciehp: Use down_read/write_nested(reset_lock) to fix lockdep errors
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@mit.edu/ Link: https://lore.kernel.org/linux-pci/de684a28-9038-8fc6-27ca-3f6f2f6400d7@redhat.com/ Link: https://lore.kernel.org/r/20211217141709.379663-1-hdegoede@redhat.com Link: https://bugzilla.kernel.org/show_bug.cgi?id=208855 Reported-by: "Theodore Ts'o" <tytso@mit.edu> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Reviewed-by: Lukas Wunner <lukas@wunner.de> Cc: stable@vger.kernel.org
Diffstat (limited to 'drivers/pci/hotplug')
-rw-r--r--drivers/pci/hotplug/pciehp.h3
-rw-r--r--drivers/pci/hotplug/pciehp_core.c2
-rw-r--r--drivers/pci/hotplug/pciehp_hpc.c21
3 files changed, 22 insertions, 4 deletions
diff --git a/drivers/pci/hotplug/pciehp.h b/drivers/pci/hotplug/pciehp.h
index 918dccbc74b6..e0a614acee05 100644
--- 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;
diff --git a/drivers/pci/hotplug/pciehp_core.c b/drivers/pci/hotplug/pciehp_core.c
index f34114d45259..4042d87d539d 100644
--- a/drivers/pci/hotplug/pciehp_core.c
+++ b/drivers/pci/hotplug/pciehp_core.c
@@ -166,7 +166,7 @@ static void pciehp_check_presence(struct controller *ctrl)
{
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);
diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index 9535c61cbff3..1d3108e6c128 100644
--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -583,7 +583,7 @@ static void pciehp_ignore_dpc_link_change(struct controller *ctrl,
* 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);
@@ -747,7 +747,7 @@ static irqreturn_t pciehp_ist(int irq, void *dev_id)
* 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))
@@ -907,7 +907,7 @@ int pciehp_reset_slot(struct hotplug_slot *hotplug_slot, bool probe)
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;
@@ -963,6 +963,20 @@ static inline void dbg_ctrl(struct controller *ctrl)
#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;
@@ -976,6 +990,7 @@ struct controller *pcie_init(struct pcie_device *dev)
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)