From 456f832e5fc26fbfd3b8200fd4553eee520cc377 Mon Sep 17 00:00:00 2001 From: Adrian Hunter Date: Fri, 7 Aug 2026 17:56:25 +0300 Subject: i3c: master: Fix recursive locking during device registration i3c_master_register_new_i3c_devs() registers newly discovered devices while holding i3c_bus_normaluse_lock(), a down_read(). device_register() can immediately probe the device, and probe callbacks typically invoke I3C helpers that take i3c_bus_normaluse_lock() again, leading to a recursive acquisition of the same rwsem. rwsems do not support recursive read locking and can deadlock when a writer is waiting. See the "Recursive read locks" section of Documentation/locking/lockdep-design.rst. For example, with Intel LPSS I3C, LOCKDEP generates a WARNING like: # echo intel-lpss-i3c.0 > /sys/bus/platform/drivers/mipi-i3c-hci/unbind # echo intel-lpss-i3c.0 > /sys/bus/platform/drivers/mipi-i3c-hci/bind WARNING: possible recursive locking detected kworker/5:1/94 is trying to acquire lock: ffff88811c810d78 (&i3cbus->lock){++++}-{4:4}, at: i3c_device_match_id+0x45/0x370 but task is already holding lock: ffff88811c810d78 (&i3cbus->lock){++++}-{4:4}, at: i3c_master_reg_work_fn+0x21/0x5f0 Fix this by separating device creation from device registration. Populate desc->dev under the maintenance lock, collect the devices that still need registration into a local list, then release the lock before calling device_register(). Finally retake the lock and clean up any devices that failed to register. Use the maintenance lock rather than the normal-use lock while adding device objects. A write-side maintenance lock prevents readers from observing a partially initialized desc->dev during initial device population, or desc->dev disappearing if registration fails. The local list requires a list node, so add a list node member to struct i3c_device. Fixes: 3a379bbcea0a ("i3c: Add core I3C infrastructure") Cc: stable@vger.kernel.org Signed-off-by: Adrian Hunter Reviewed-by: Frank Li Link: https://patch.msgid.link/20260807145638.168865-2-adrian.hunter@intel.com Signed-off-by: Alexandre Belloni --- include/linux/i3c/master.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include') diff --git a/include/linux/i3c/master.h b/include/linux/i3c/master.h index 2dc139a217bf..26535beb1e77 100644 --- a/include/linux/i3c/master.h +++ b/include/linux/i3c/master.h @@ -238,6 +238,8 @@ struct i3c_dev_desc { * every time the I3C device is rediscovered with a different dynamic * address assigned * @bus: I3C bus this device is attached to + * @node: unregistered device list node, only for use by + * i3c_master_register_new_i3c_devs(), it is not protected by a lock * * I3C device object exposed to I3C device drivers. The takes care of linking * this object to the relevant &struct_i3c_dev_desc one. @@ -248,6 +250,7 @@ struct i3c_device { struct device dev; struct i3c_dev_desc *desc; struct i3c_bus *bus; + struct list_head node; }; /* -- cgit v1.2.3