From d0ff1c04e8e6b56eb75bf6c221a98ab939ff5e13 Mon Sep 17 00:00:00 2001 From: Pavankumar Kondeti Date: Mon, 28 Nov 2016 20:55:58 +0530 Subject: [PATCH] sched: Disable interrupts while holding related_thread_group_lock There is a potential deadlock condition if interrupts are enabled while holding the related_thread_group_lock. Prevent this. ---------------- -------------------- CPU 0 CPU 1 --------------- -------------------- check_for_migration() cgroup_file_write(p) check_for_freq_change() cgroup_attach_task(p) send_notification() schedtune_attach(p) read_lock(&related_thread_group_lock) sched_set_group_id(p) raw_spin_lock_irqsave( &p->pi_lock, flags) write_lock_irqsave( &related_thread_group_lock) waiting on CPU#0 raw_spin_lock_irqsave(&rq->lock, flags) raw_spin_unlock_irqrestore(&rq->lock, flags) --> interrupt() ----> ttwu(p) -------> waiting for p's pi_lock on CPU#1 Change-Id: I6f0f8f742d6e1b3ff735dcbeabd54ef101329cdf Signed-off-by: Pavankumar Kondeti --- kernel/sched/hmp.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/kernel/sched/hmp.c b/kernel/sched/hmp.c index 968a41e0e81e..ad5d115bdd7f 100644 --- a/kernel/sched/hmp.c +++ b/kernel/sched/hmp.c @@ -1767,20 +1767,20 @@ static int send_notification(struct rq *rq, int check_pred, int check_groups) if (freq_required < cur_freq + sysctl_sched_pred_alert_freq) return 0; } else { - read_lock(&related_thread_group_lock); + read_lock_irqsave(&related_thread_group_lock, flags); /* * Protect from concurrent update of rq->prev_runnable_sum and * group cpu load */ - raw_spin_lock_irqsave(&rq->lock, flags); + raw_spin_lock(&rq->lock); if (check_groups) _group_load_in_cpu(cpu_of(rq), &group_load, NULL); new_load = rq->prev_runnable_sum + group_load; new_load = freq_policy_load(rq, new_load); - raw_spin_unlock_irqrestore(&rq->lock, flags); - read_unlock(&related_thread_group_lock); + raw_spin_unlock(&rq->lock); + read_unlock_irqrestore(&related_thread_group_lock, flags); cur_freq = load_to_freq(rq, rq->old_busy_time); freq_required = load_to_freq(rq, new_load); @@ -3202,14 +3202,16 @@ void sched_get_cpus_busy(struct sched_load *busy, if (unlikely(cpus == 0)) return; + local_irq_save(flags); + + read_lock(&related_thread_group_lock); + /* * This function could be called in timer context, and the * current task may have been executing for a long time. Ensure * that the window stats are current by doing an update. */ - read_lock(&related_thread_group_lock); - local_irq_save(flags); for_each_cpu(cpu, query_cpus) raw_spin_lock(&cpu_rq(cpu)->lock); @@ -3309,10 +3311,11 @@ skip_early: for_each_cpu(cpu, query_cpus) raw_spin_unlock(&(cpu_rq(cpu))->lock); - local_irq_restore(flags); read_unlock(&related_thread_group_lock); + local_irq_restore(flags); + i = 0; for_each_cpu(cpu, query_cpus) { rq = cpu_rq(cpu);