linux-kernel - [tip: locking/core] sched: Constrain locks in sched_submit

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Message-ID: <169519537258.27769.828089056891859325.tip-bot2@tip-bot2>
Date:   Wed, 20 Sep 2023 07:36:12 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: locking/core] sched: Constrain locks in sched_submit_work()

The following commit has been merged into the locking/core branch of tip:

Commit-ID:     28bc55f654de49f6122c7475b01b5d5ef4bdf0d4
Gitweb:        https://git.kernel.org/tip/28bc55f654de49f6122c7475b01b5d5ef4bdf0d4
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Fri, 08 Sep 2023 18:22:48 +02:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Wed, 20 Sep 2023 09:31:11 +02:00

sched: Constrain locks in sched_submit_work()

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@...radead.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lkml.kernel.org/r/20230908162254.999499-2-bigeasy@linutronix.de
---
 kernel/sched/core.c |  9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 2299a5c..d555640 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6720,11 +6720,18 @@ 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
@@ -6749,6 +6756,8 @@ 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)