[PATCH v2 1/6] sched: Constrain locks in sched_submit_work()

[Sebastian Andrzej Siewior]

From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>

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)" <peterz@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230815111430.154558666@xxxxxxxxxxxxx
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
 kernel/sched/core.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c52c2eba7c739..bca53ff9d8182 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6735,11 +6735,18 @@ 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
@@ -6764,6 +6771,8 @@ static inline void sched_submit_work(struct task_struct *tsk)
 	 * 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)
-- 
2.40.1