From: Wander Lairson Costa <wander@xxxxxxxxxx> v5.15.133-rt70-rc1 stable review patch. If anyone has any objections, please let me know. ----------- In put_task_struct(), a spin_lock is indirectly acquired under the kernel stock. When running the kernel in real-time (RT) configuration, the operation is dispatched to a preemptible context call to ensure guaranteed preemption. However, if PROVE_RAW_LOCK_NESTING is enabled and __put_task_struct() is called while holding a raw_spinlock, lockdep incorrectly reports an "Invalid lock context" in the stock kernel. This false splat occurs because lockdep is unaware of the different route taken under RT. To address this issue, override the inner wait type to prevent the false lockdep splat. Suggested-by: Oleg Nesterov <oleg@xxxxxxxxxx> Suggested-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Signed-off-by: Wander Lairson Costa <wander@xxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20230614122323.37957-3-wander@xxxxxxxxxx (cherry picked from commit 893cdaaa3977be6afb3a7f756fbfd7be83f68d8c) Signed-off-by: Joseph Salisbury <joseph.salisbury@xxxxxxxxxxxxx> --- include/linux/sched/task.h | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h index 0c2d00809915..75d52a9e7620 100644 --- a/include/linux/sched/task.h +++ b/include/linux/sched/task.h @@ -115,6 +115,19 @@ static inline void put_task_struct(struct task_struct *t) if (!refcount_dec_and_test(&t->usage)) return; + /* + * In !RT, it is always safe to call __put_task_struct(). + * Under RT, we can only call it in preemptible context. + */ + if (!IS_ENABLED(CONFIG_PREEMPT_RT) || preemptible()) { + static DEFINE_WAIT_OVERRIDE_MAP(put_task_map, LD_WAIT_SLEEP); + + lock_map_acquire_try(&put_task_map); + __put_task_struct(t); + lock_map_release(&put_task_map); + return; + } + /* * under PREEMPT_RT, we can't call put_task_struct * in atomic context because it will indirectly @@ -135,10 +148,7 @@ static inline void put_task_struct(struct task_struct *t) * when it fails to fork a process. Therefore, there is no * way it can conflict with put_task_struct(). */ - if (IS_ENABLED(CONFIG_PREEMPT_RT) && !preemptible()) - call_rcu(&t->rcu, __put_task_struct_rcu_cb); - else - __put_task_struct(t); + call_rcu(&t->rcu, __put_task_struct_rcu_cb); } static inline void put_task_struct_many(struct task_struct *t, int nr) -- 2.34.1
