From: Mika Westerberg mika.westerberg@linux.intel.com
[ Upstream commit 87d0f2a5536fdf5053a6d341880f96135549a644 ]
This addresses deadlocks in these common cases in hierarchies containing two switches:
- All involved ports are runtime suspended and they are unplugged. This can happen easily if the drivers involved automatically enable runtime PM (xHCI for example does that).
- System is suspended (e.g., closing the lid on a laptop) with a dock + something else connected, and the dock is unplugged while suspended.
These cases lead to the following deadlock:
INFO: task irq/126-pciehp:198 blocked for more than 120 seconds. irq/126-pciehp D 0 198 2 0x80000000 Call Trace: schedule+0x2c/0x80 schedule_timeout+0x246/0x350 wait_for_completion+0xb7/0x140 kthread_stop+0x49/0x110 free_irq+0x32/0x70 pcie_shutdown_notification+0x2f/0x50 pciehp_remove+0x27/0x50 pcie_port_remove_service+0x36/0x50 device_release_driver+0x12/0x20 bus_remove_device+0xec/0x160 device_del+0x13b/0x350 device_unregister+0x1a/0x60 remove_iter+0x1e/0x30 device_for_each_child+0x56/0x90 pcie_port_device_remove+0x22/0x40 pcie_portdrv_remove+0x20/0x60 pci_device_remove+0x3e/0xc0 device_release_driver_internal+0x18c/0x250 device_release_driver+0x12/0x20 pci_stop_bus_device+0x6f/0x90 pci_stop_bus_device+0x31/0x90 pci_stop_and_remove_bus_device+0x12/0x20 pciehp_unconfigure_device+0x88/0x140 pciehp_disable_slot+0x6a/0x110 pciehp_handle_presence_or_link_change+0x263/0x400 pciehp_ist+0x1c9/0x1d0 irq_thread_fn+0x24/0x60 irq_thread+0xeb/0x190 kthread+0x120/0x140
INFO: task irq/190-pciehp:2288 blocked for more than 120 seconds. irq/190-pciehp D 0 2288 2 0x80000000 Call Trace: __schedule+0x2a2/0x880 schedule+0x2c/0x80 schedule_preempt_disabled+0xe/0x10 mutex_lock+0x2c/0x30 pci_lock_rescan_remove+0x15/0x20 pciehp_unconfigure_device+0x4d/0x140 pciehp_disable_slot+0x6a/0x110 pciehp_handle_presence_or_link_change+0x263/0x400 pciehp_ist+0x1c9/0x1d0 irq_thread_fn+0x24/0x60 irq_thread+0xeb/0x190 kthread+0x120/0x140
What happens here is that the whole hierarchy is runtime resumed and the parent PCIe downstream port, which got the hot-remove event, starts removing devices below it, taking pci_lock_rescan_remove() lock. When the child PCIe port is runtime resumed it calls pciehp_check_presence() which ends up calling pciehp_card_present() and pciehp_check_link_active(). Both of these use pcie_capability_read_word(), which notices that the underlying device is already gone and returns PCIBIOS_DEVICE_NOT_FOUND with the capability value set to 0. When pciehp gets this value it thinks that its child device is also hot-removed and schedules its IRQ thread to handle the event.
The deadlock happens when the child's IRQ thread runs and tries to acquire pci_lock_rescan_remove() which is already taken by the parent and the parent waits for the child's IRQ thread to finish.
Prevent this from happening by checking the return value of pcie_capability_read_word() and if it is PCIBIOS_DEVICE_NOT_FOUND stop performing any hot-removal activities.
[bhelgaas: add common scenarios to commit log] Link: https://lore.kernel.org/r/20191029170022.57528-2-mika.westerberg@linux.intel... Tested-by: Kai-Heng Feng kai.heng.feng@canonical.com Signed-off-by: Mika Westerberg mika.westerberg@linux.intel.com Signed-off-by: Bjorn Helgaas bhelgaas@google.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/pci/hotplug/pciehp.h | 6 ++-- drivers/pci/hotplug/pciehp_core.c | 11 ++++-- drivers/pci/hotplug/pciehp_ctrl.c | 4 +-- drivers/pci/hotplug/pciehp_hpc.c | 59 +++++++++++++++++++++++++------ 4 files changed, 61 insertions(+), 19 deletions(-)
diff --git a/drivers/pci/hotplug/pciehp.h b/drivers/pci/hotplug/pciehp.h index 882ce82c46990..aa61d4c219d7b 100644 --- a/drivers/pci/hotplug/pciehp.h +++ b/drivers/pci/hotplug/pciehp.h @@ -174,10 +174,10 @@ void pciehp_set_indicators(struct controller *ctrl, int pwr, int attn);
void pciehp_get_latch_status(struct controller *ctrl, u8 *status); int pciehp_query_power_fault(struct controller *ctrl); -bool pciehp_card_present(struct controller *ctrl); -bool pciehp_card_present_or_link_active(struct controller *ctrl); +int pciehp_card_present(struct controller *ctrl); +int pciehp_card_present_or_link_active(struct controller *ctrl); int pciehp_check_link_status(struct controller *ctrl); -bool pciehp_check_link_active(struct controller *ctrl); +int pciehp_check_link_active(struct controller *ctrl); void pciehp_release_ctrl(struct controller *ctrl);
int pciehp_sysfs_enable_slot(struct hotplug_slot *hotplug_slot); diff --git a/drivers/pci/hotplug/pciehp_core.c b/drivers/pci/hotplug/pciehp_core.c index 56daad828c9e0..312cc45c44c78 100644 --- a/drivers/pci/hotplug/pciehp_core.c +++ b/drivers/pci/hotplug/pciehp_core.c @@ -139,10 +139,15 @@ static int get_adapter_status(struct hotplug_slot *hotplug_slot, u8 *value) { struct controller *ctrl = to_ctrl(hotplug_slot); struct pci_dev *pdev = ctrl->pcie->port; + int ret;
pci_config_pm_runtime_get(pdev); - *value = pciehp_card_present_or_link_active(ctrl); + ret = pciehp_card_present_or_link_active(ctrl); pci_config_pm_runtime_put(pdev); + if (ret < 0) + return ret; + + *value = ret; return 0; }
@@ -158,13 +163,13 @@ static int get_adapter_status(struct hotplug_slot *hotplug_slot, u8 *value) */ static void pciehp_check_presence(struct controller *ctrl) { - bool occupied; + int occupied;
down_read(&ctrl->reset_lock); mutex_lock(&ctrl->state_lock);
occupied = pciehp_card_present_or_link_active(ctrl); - if ((occupied && (ctrl->state == OFF_STATE || + if ((occupied > 0 && (ctrl->state == OFF_STATE || ctrl->state == BLINKINGON_STATE)) || (!occupied && (ctrl->state == ON_STATE || ctrl->state == BLINKINGOFF_STATE))) diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c index dd8e4a5fb2826..6503d15effbbd 100644 --- a/drivers/pci/hotplug/pciehp_ctrl.c +++ b/drivers/pci/hotplug/pciehp_ctrl.c @@ -226,7 +226,7 @@ void pciehp_handle_disable_request(struct controller *ctrl)
void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events) { - bool present, link_active; + int present, link_active;
/* * If the slot is on and presence or link has changed, turn it off. @@ -257,7 +257,7 @@ void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events) mutex_lock(&ctrl->state_lock); present = pciehp_card_present(ctrl); link_active = pciehp_check_link_active(ctrl); - if (!present && !link_active) { + if (present <= 0 && link_active <= 0) { mutex_unlock(&ctrl->state_lock); return; } diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c index d74a71712cde4..356786a3b7f4b 100644 --- a/drivers/pci/hotplug/pciehp_hpc.c +++ b/drivers/pci/hotplug/pciehp_hpc.c @@ -201,17 +201,29 @@ static void pcie_write_cmd_nowait(struct controller *ctrl, u16 cmd, u16 mask) pcie_do_write_cmd(ctrl, cmd, mask, false); }
-bool pciehp_check_link_active(struct controller *ctrl) +/** + * pciehp_check_link_active() - Is the link active + * @ctrl: PCIe hotplug controller + * + * Check whether the downstream link is currently active. Note it is + * possible that the card is removed immediately after this so the + * caller may need to take it into account. + * + * If the hotplug controller itself is not available anymore returns + * %-ENODEV. + */ +int pciehp_check_link_active(struct controller *ctrl) { struct pci_dev *pdev = ctrl_dev(ctrl); u16 lnk_status; - bool ret; + int ret;
- pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status); - ret = !!(lnk_status & PCI_EXP_LNKSTA_DLLLA); + ret = pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status); + if (ret == PCIBIOS_DEVICE_NOT_FOUND || lnk_status == (u16)~0) + return -ENODEV;
- if (ret) - ctrl_dbg(ctrl, "%s: lnk_status = %x\n", __func__, lnk_status); + ret = !!(lnk_status & PCI_EXP_LNKSTA_DLLLA); + ctrl_dbg(ctrl, "%s: lnk_status = %x\n", __func__, lnk_status);
return ret; } @@ -373,13 +385,29 @@ void pciehp_get_latch_status(struct controller *ctrl, u8 *status) *status = !!(slot_status & PCI_EXP_SLTSTA_MRLSS); }
-bool pciehp_card_present(struct controller *ctrl) +/** + * pciehp_card_present() - Is the card present + * @ctrl: PCIe hotplug controller + * + * Function checks whether the card is currently present in the slot and + * in that case returns true. Note it is possible that the card is + * removed immediately after the check so the caller may need to take + * this into account. + * + * It the hotplug controller itself is not available anymore returns + * %-ENODEV. + */ +int pciehp_card_present(struct controller *ctrl) { struct pci_dev *pdev = ctrl_dev(ctrl); u16 slot_status; + int ret;
- pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &slot_status); - return slot_status & PCI_EXP_SLTSTA_PDS; + ret = pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &slot_status); + if (ret == PCIBIOS_DEVICE_NOT_FOUND || slot_status == (u16)~0) + return -ENODEV; + + return !!(slot_status & PCI_EXP_SLTSTA_PDS); }
/** @@ -390,10 +418,19 @@ bool pciehp_card_present(struct controller *ctrl) * Presence Detect State bit, this helper also returns true if the Link Active * bit is set. This is a concession to broken hotplug ports which hardwire * Presence Detect State to zero, such as Wilocity's [1ae9:0200]. + * + * Returns: %1 if the slot is occupied and %0 if it is not. If the hotplug + * port is not present anymore returns %-ENODEV. */ -bool pciehp_card_present_or_link_active(struct controller *ctrl) +int pciehp_card_present_or_link_active(struct controller *ctrl) { - return pciehp_card_present(ctrl) || pciehp_check_link_active(ctrl); + int ret; + + ret = pciehp_card_present(ctrl); + if (ret) + return ret; + + return pciehp_check_link_active(ctrl); }
int pciehp_query_power_fault(struct controller *ctrl)