From: Dan Williams dan.j.williams@intel.com
[ Upstream commit e6829d1bd3c4b58296ee9e412f7ed4d6cb390192 ]
Lockdep reports the following deadlock scenarios for CXL root device power-management, device_prepare(), operations, and device_shutdown() operations for 'nd_region' devices:
Chain exists of: &nvdimm_region_key --> &nvdimm_bus->reconfig_mutex --> system_transition_mutex
Possible unsafe locking scenario:
CPU0 CPU1 ---- ---- lock(system_transition_mutex); lock(&nvdimm_bus->reconfig_mutex); lock(system_transition_mutex); lock(&nvdimm_region_key);
Chain exists of: &cxl_nvdimm_bridge_key --> acpi_scan_lock --> &cxl_root_key
Possible unsafe locking scenario:
CPU0 CPU1 ---- ---- lock(&cxl_root_key); lock(acpi_scan_lock); lock(&cxl_root_key); lock(&cxl_nvdimm_bridge_key);
These stem from holding nvdimm_bus_lock() over hibernate_quiet_exec() which walks the entire system device topology taking device_lock() along the way. The nvdimm_bus_lock() is protecting against unregistration, multiple simultaneous ops callers, and preventing activate_show() from racing activate_store(). For the first 2, the lock is redundant. Unregistration already flushes all ops users, and sysfs already prevents multiple threads to be active in an ops handler at the same time. For the last userspace should already be waiting for its last activate_store() to complete, and does not need activate_show() to flush the write side, so this lock usage can be deleted in these attributes.
Fixes: 48001ea50d17 ("PM, libnvdimm: Add runtime firmware activation support") Reviewed-by: Ira Weiny ira.weiny@intel.com Link: https://lore.kernel.org/r/165074883800.4116052.10737040861825806582.stgit@dw... Signed-off-by: Dan Williams dan.j.williams@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/nvdimm/core.c | 9 --------- 1 file changed, 9 deletions(-)
diff --git a/drivers/nvdimm/core.c b/drivers/nvdimm/core.c index 69a03358817f..681cc28703a3 100644 --- a/drivers/nvdimm/core.c +++ b/drivers/nvdimm/core.c @@ -368,9 +368,7 @@ static ssize_t capability_show(struct device *dev, if (!nd_desc->fw_ops) return -EOPNOTSUPP;
- nvdimm_bus_lock(dev); cap = nd_desc->fw_ops->capability(nd_desc); - nvdimm_bus_unlock(dev);
switch (cap) { case NVDIMM_FWA_CAP_QUIESCE: @@ -395,10 +393,8 @@ static ssize_t activate_show(struct device *dev, if (!nd_desc->fw_ops) return -EOPNOTSUPP;
- nvdimm_bus_lock(dev); cap = nd_desc->fw_ops->capability(nd_desc); state = nd_desc->fw_ops->activate_state(nd_desc); - nvdimm_bus_unlock(dev);
if (cap < NVDIMM_FWA_CAP_QUIESCE) return -EOPNOTSUPP; @@ -443,7 +439,6 @@ static ssize_t activate_store(struct device *dev, else return -EINVAL;
- nvdimm_bus_lock(dev); state = nd_desc->fw_ops->activate_state(nd_desc);
switch (state) { @@ -461,7 +456,6 @@ static ssize_t activate_store(struct device *dev, default: rc = -ENXIO; } - nvdimm_bus_unlock(dev);
if (rc == 0) rc = len; @@ -484,10 +478,7 @@ static umode_t nvdimm_bus_firmware_visible(struct kobject *kobj, struct attribut if (!nd_desc->fw_ops) return 0;
- nvdimm_bus_lock(dev); cap = nd_desc->fw_ops->capability(nd_desc); - nvdimm_bus_unlock(dev); - if (cap < NVDIMM_FWA_CAP_QUIESCE) return 0;