From: Peter Zijlstra Date: Fri, 8 Sep 2023 18:22:48 +0200 Subject: [PATCH 1/7] sched: Constrain locks in sched_submit_work() Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.6/older/patches-6.6.7-rt18.tar.xz Even though sched_submit_work() is ran from preemptible context, it is discouraged to have it use blocking locks due to the recursion potential. Enforce this. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20230908162254.999499-2-bigeasy@linutronix.de --- kernel/sched/core.c | 9 +++++++++ 1 file changed, 9 insertions(+) --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6721,11 +6721,18 @@ void __noreturn do_task_dead(void) static inline void sched_submit_work(struct task_struct *tsk) { + static DEFINE_WAIT_OVERRIDE_MAP(sched_map, LD_WAIT_CONFIG); unsigned int task_flags; if (task_is_running(tsk)) return; + /* + * Establish LD_WAIT_CONFIG context to ensure none of the code called + * will use a blocking primitive -- which would lead to recursion. + */ + lock_map_acquire_try(&sched_map); + task_flags = tsk->flags; /* * If a worker goes to sleep, notify and ask workqueue whether it @@ -6750,6 +6757,8 @@ static inline void sched_submit_work(str * make sure to submit it to avoid deadlocks. */ blk_flush_plug(tsk->plug, true); + + lock_map_release(&sched_map); } static void sched_update_worker(struct task_struct *tsk)