Some kernel functions must not be called holding a specific lock. Doing so could lead to locking problems. Currently these routines call lock_is_held() to check for lock hold followed by WARN_ON. Adding a common lockdep interface will help reduce the duplication of this logic in the rest of the kernel. Add lockdep_assert_not_held() to be used in these functions to detect incorrect calls while holding a lock. lockdep_assert_not_held() provides the opposite functionality of lockdep_assert_held() which is used to assert calls that require holding a specific lock. The need for lockdep_assert_not_held() came up in a discussion on ath10k patch. ath10k_drain_tx() and i915_vma_pin_ww() are examples of functions that can use lockdep_assert_not_held(). Link: https://lore.kernel.org/lkml/37a29c383bff2fb1605241ee6c7c9be3784fb3c6.1613171185.git.skhan@xxxxxxxxxxxxxxxxxxx/ Link: https://lore.kernel.org/linux-wireless/871rdmu9z9.fsf@xxxxxxxxxxxxxx/ This patch series adds lockdep_assert_not_held() and uses it in the second patch in ath10k_drain_tx() function. Patch 1 incorporates suggestions from Peter Zijlstra on v1 series to avoid misfires when lockdep_off() is employed. Patch 2 Johannes Berg's suggestions as it make it easier to read and maintain the lock states. These are defines and a enum to avoid changes to lock_is_held_type() and lockdep_is_held() return types. Patch 2 is a separate patch because it adds defines to lockdep.h and kernel/locking/lockdep.c now includes lockdep.h - decided make this a separate patch just in case issues related to header dependencies pop up. I can combine Patches 1&2 if that is preferred. Patch 3 uses the new interface in ath10k_drain_tx() function. Added Kalle Valo's Ack from v1 for this change. Tested on the mainline from yesterday. Shuah Khan (3): lockdep: add lockdep_assert_not_held() lockdep: add lockdep lock state defines ath10k: detect conf_mutex held ath10k_drain_tx() calls drivers/net/wireless/ath/ath10k/mac.c | 2 ++ include/linux/lockdep.h | 18 +++++++++++++++--- kernel/locking/lockdep.c | 6 +++++- 3 files changed, 22 insertions(+), 4 deletions(-) -- 2.27.0
