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charset="utf-8" When the rq lock is held and a printk occurs, some console drivers may trigger a deadlock by calling into scheduler functions (e.g. scheduling work). Though printk() is avoided in these contexts, there are some WARN or WARN_ONCE statements which can trigger deadlocks during context switch operations. These warnings should not trigger deadlocks. Use the printk_deferred helper to ensure console drivers aren't called until after the critical section is over. Signed-off-by: Stephen Brennan --- kernel/sched/core.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 848eaa0efe0e..bc8afc3020a4 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4861,6 +4861,7 @@ static struct rq *finish_task_switch(struct task_stru= ct *prev) perf_event_task_sched_in(prev, current); finish_task(prev); tick_nohz_task_switch(); + printk_deferred_exit(); finish_lock_switch(rq); finish_arch_post_lock_switch(); kcov_finish_switch(current); @@ -6208,6 +6209,7 @@ static void __sched notrace __schedule(unsigned int s= ched_mode) */ rq_lock(rq, &rf); smp_mb__after_spinlock(); + printk_deferred_enter(); =20 /* Promote REQ to ACT */ rq->clock_update_flags <<=3D 1; @@ -6298,6 +6300,7 @@ static void __sched notrace __schedule(unsigned int s= ched_mode) =20 rq_unpin_lock(rq, &rf); __balance_callbacks(rq); + printk_deferred_exit(); raw_spin_rq_unlock_irq(rq); } } --=20 2.30.2