From: Lukas Wunner lukas@wunner.de
commit 74ff8864cc842be994853095dba6db48e716400a upstream.
On surprise removal, pciehp_unconfigure_device() and acpiphp's trim_stale_devices() call pci_dev_set_disconnected() to mark removed devices as permanently offline. Thereby, the PCI core and drivers know to skip device accesses.
However pci_dev_set_disconnected() takes the device_lock and thus waits for a concurrent driver bind or unbind to complete. As a result, the driver's ->probe and ->remove hooks have no chance to learn that the device is gone.
That doesn't make any sense, so drop the device_lock and instead use atomic xchg() and cmpxchg() operations to update the device state.
As a byproduct, an AB-BA deadlock reported by Anatoli is fixed which occurs on surprise removal with AER concurrently performing a bus reset.
AER bus reset:
INFO: task irq/26-aerdrv:95 blocked for more than 120 seconds. Tainted: G W 6.2.0-rc3-custom-norework-jan11+ schedule rwsem_down_write_slowpath down_write_nested pciehp_reset_slot # acquires reset_lock pci_reset_hotplug_slot pci_slot_reset # acquires device_lock pci_bus_error_reset aer_root_reset pcie_do_recovery aer_process_err_devices aer_isr
pciehp surprise removal:
INFO: task irq/26-pciehp:96 blocked for more than 120 seconds. Tainted: G W 6.2.0-rc3-custom-norework-jan11+ schedule_preempt_disabled __mutex_lock mutex_lock_nested pci_dev_set_disconnected # acquires device_lock pci_walk_bus pciehp_unconfigure_device pciehp_disable_slot pciehp_handle_presence_or_link_change pciehp_ist # acquires reset_lock
Link: https://bugzilla.kernel.org/show_bug.cgi?id=215590 Fixes: a6bd101b8f84 ("PCI: Unify device inaccessible") Link: https://lore.kernel.org/r/3dc88ea82bdc0e37d9000e413d5ebce481cbd629.167420568... Reported-by: Anatoli Antonovitch anatoli.antonovitch@amd.com Signed-off-by: Lukas Wunner lukas@wunner.de Signed-off-by: Bjorn Helgaas bhelgaas@google.com Cc: stable@vger.kernel.org # v4.20+ Cc: Keith Busch kbusch@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/pci/pci.h | 43 +++++++++++++------------------------------ 1 file changed, 13 insertions(+), 30 deletions(-)
--- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -347,53 +347,36 @@ struct pci_sriov { * @dev: PCI device to set new error_state * @new: the state we want dev to be in * - * Must be called with device_lock held. + * If the device is experiencing perm_failure, it has to remain in that state. + * Any other transition is allowed. * * Returns true if state has been changed to the requested state. */ static inline bool pci_dev_set_io_state(struct pci_dev *dev, pci_channel_state_t new) { - bool changed = false; + pci_channel_state_t old;
- device_lock_assert(&dev->dev); switch (new) { case pci_channel_io_perm_failure: - switch (dev->error_state) { - case pci_channel_io_frozen: - case pci_channel_io_normal: - case pci_channel_io_perm_failure: - changed = true; - break; - } - break; + xchg(&dev->error_state, pci_channel_io_perm_failure); + return true; case pci_channel_io_frozen: - switch (dev->error_state) { - case pci_channel_io_frozen: - case pci_channel_io_normal: - changed = true; - break; - } - break; + old = cmpxchg(&dev->error_state, pci_channel_io_normal, + pci_channel_io_frozen); + return old != pci_channel_io_perm_failure; case pci_channel_io_normal: - switch (dev->error_state) { - case pci_channel_io_frozen: - case pci_channel_io_normal: - changed = true; - break; - } - break; + old = cmpxchg(&dev->error_state, pci_channel_io_frozen, + pci_channel_io_normal); + return old != pci_channel_io_perm_failure; + default: + return false; } - if (changed) - dev->error_state = new; - return changed; }
static inline int pci_dev_set_disconnected(struct pci_dev *dev, void *unused) { - device_lock(&dev->dev); pci_dev_set_io_state(dev, pci_channel_io_perm_failure); - device_unlock(&dev->dev);
return 0; }