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-rw-r--r--0005-PCI-pciehp-Prevent-deadlock-on-disconnect.patch272
1 files changed, 272 insertions, 0 deletions
diff --git a/0005-PCI-pciehp-Prevent-deadlock-on-disconnect.patch b/0005-PCI-pciehp-Prevent-deadlock-on-disconnect.patch
new file mode 100644
index 00000000000..e0635955c31
--- /dev/null
+++ b/0005-PCI-pciehp-Prevent-deadlock-on-disconnect.patch
@@ -0,0 +1,272 @@
+From c5d7bb41ce34e4d00c31a8d2a4728a2fdef1216c Mon Sep 17 00:00:00 2001
+From: Mika Westerberg <mika.westerberg@linux.intel.com>
+Date: Tue, 29 Oct 2019 20:00:22 +0300
+Subject: [PATCH 5/6] PCI: pciehp: Prevent deadlock on disconnect
+
+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.com
+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>
+---
+ 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 654c972b8ea0..afea59a3aad2 100644
+--- a/drivers/pci/hotplug/pciehp.h
++++ b/drivers/pci/hotplug/pciehp.h
+@@ -172,10 +172,10 @@ 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 56daad828c9e..312cc45c44c7 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 21af7b16d7a4..c760a13ec7b1 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 1a522c1c4177..526a8f70bac5 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)
+--
+2.24.0
+