From: Tarun Sahu <[email protected]> In Async device shutdown, device_kset->list lock is released to handle asynchronisation and hold again to get entry from device_kset->list. Which will leave window when device_add can try to add the device to device_kset list and temper with ongoing shutdown process. New added device can be async type or sync type and might also introduce new dependency which can cause device_shutdown path to deadlock. S is waiting C to finish but C is never scheduled as it was added recently from device_add path. And C can only be scheduled when main loops continue to reach to C which is waiting on S.
So, When a system enters shutdown (SYSTEM_HALT, SYSTEM_POWER_OFF, or SYSTEM_RESTART), new devices should not be allowed to be added. Adding system_state check (system_is_shutting_down()) to avoid device_add incase of these states of the system. And use srcu so the device shutdown operation can synchronize device_add and ensure any device_add in progress is finished. Signed-off-by: Tarun Sahu <[email protected]> Signed-off-by: David Jeffery <[email protected]> Tested-by: Laurence Oberman <[email protected]> --- drivers/base/core.c | 30 +++++++++++++++++++++++++++++- 1 file changed, 29 insertions(+), 1 deletion(-) diff --git a/drivers/base/core.c b/drivers/base/core.c index 83263e3fa5d4..bce555dd74f6 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -47,6 +47,22 @@ static bool fw_devlink_drv_reg_done; static bool fw_devlink_best_effort; static struct workqueue_struct *device_link_wq; +/** + * system_is_shutting_down - Check if system state is not active. + * + * When system state is not active and in shutdown state, new devices + * should not be allowed to be added. + * + * If system_state is SYSTEM_HALT || SYSTEM_POWER_OFF || SYSTEM_RESTART + * this function will return true. + */ +static inline bool system_is_shutting_down(void) +{ + return system_state == SYSTEM_HALT || + system_state == SYSTEM_POWER_OFF || + system_state == SYSTEM_RESTART; +} + /** * __fwnode_link_add - Create a link between two fwnode_handles. * @con: Consumer end of the link. @@ -3614,6 +3630,9 @@ static int device_private_init(struct device *dev) return 0; } + +DEFINE_STATIC_SRCU(device_add_srcu); + /** * device_add - add device to device hierarchy. * @dev: device. @@ -3647,13 +3666,20 @@ int device_add(struct device *dev) struct device *parent; struct kobject *kobj; struct class_interface *class_intf; - int error = -EINVAL; + int idx, error = -EINVAL; struct kobject *glue_dir = NULL; + idx = srcu_read_lock(&device_add_srcu); + dev = get_device(dev); if (!dev) goto done; + if (unlikely(system_is_shutting_down())) { + error = -ESHUTDOWN; + goto done; + } + if (!dev->p) { error = device_private_init(dev); if (error) @@ -3803,6 +3829,7 @@ int device_add(struct device *dev) } done: put_device(dev); + srcu_read_unlock(&device_add_srcu, idx); return error; SysEntryError: if (MAJOR(dev->devt)) @@ -4877,6 +4904,7 @@ void device_shutdown(void) wait_for_device_probe(); device_block_probing(); + synchronize_srcu(&device_add_srcu); cpufreq_suspend(); -- 2.55.0
