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From: Peter Zijlstra <peterz@infradead.org>
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) <peterz@infradead.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
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)
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