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sched: Disable interrupts while holding related_thread_group_lock

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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 <pkondeti@codeaurora.org>
This commit is contained in:
Pavankumar Kondeti 2016-11-28 20:55:58 +05:30 • committed by Syed Rameez Mustafa
commit 56ea74ecec
1 changed files with 10 additions and 7 deletions
Download patch file Download diff file Expand all files Collapse all files

17
kernel/sched/hmp.c
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@ -1745,20 +1745,20 @@ 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);
@ -3180,14 +3180,16 @@ 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);
@ -3287,10 +3289,11 @@ 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);