From: "tip-bot2 for Zhaoyang Huang" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: "ziwei.dai" <ziwei.dai@unisoc.com>,
"ke.wang" <ke.wang@unisoc.com>,
Zhaoyang Huang <zhaoyang.huang@unisoc.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Suren Baghdasaryan <surenb@google.com>,
Johannes Weiner <hannes@cmpxchg.org>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip: sched/core] psi: Fix race between psi_trigger_create/destroy
Date: Thu, 24 Jun 2021 07:39:26 -0000 [thread overview]
Message-ID: <162452036638.395.9852468553852116430.tip-bot2@tip-bot2> (raw)
In-Reply-To: <1623371374-15664-1-git-send-email-huangzhaoyang@gmail.com>
The following commit has been merged into the sched/core branch of tip:
Commit-ID: 8f91efd870ea5d8bc10b0fcc9740db51cd4c0c83
Gitweb: https://git.kernel.org/tip/8f91efd870ea5d8bc10b0fcc9740db51cd4c0c83
Author: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
AuthorDate: Fri, 11 Jun 2021 08:29:34 +08:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Thu, 24 Jun 2021 09:07:50 +02:00
psi: Fix race between psi_trigger_create/destroy
Race detected between psi_trigger_destroy/create as shown below, which
cause panic by accessing invalid psi_system->poll_wait->wait_queue_entry
and psi_system->poll_timer->entry->next. Under this modification, the
race window is removed by initialising poll_wait and poll_timer in
group_init which are executed only once at beginning.
psi_trigger_destroy() psi_trigger_create()
mutex_lock(trigger_lock);
rcu_assign_pointer(poll_task, NULL);
mutex_unlock(trigger_lock);
mutex_lock(trigger_lock);
if (!rcu_access_pointer(group->poll_task)) {
timer_setup(poll_timer, poll_timer_fn, 0);
rcu_assign_pointer(poll_task, task);
}
mutex_unlock(trigger_lock);
synchronize_rcu();
del_timer_sync(poll_timer); <-- poll_timer has been reinitialized by
psi_trigger_create()
So, trigger_lock/RCU correctly protects destruction of
group->poll_task but misses this race affecting poll_timer and
poll_wait.
Fixes: 461daba06bdc ("psi: eliminate kthread_worker from psi trigger scheduling mechanism")
Co-developed-by: ziwei.dai <ziwei.dai@unisoc.com>
Signed-off-by: ziwei.dai <ziwei.dai@unisoc.com>
Co-developed-by: ke.wang <ke.wang@unisoc.com>
Signed-off-by: ke.wang <ke.wang@unisoc.com>
Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lkml.kernel.org/r/1623371374-15664-1-git-send-email-huangzhaoyang@gmail.com
---
kernel/sched/psi.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index cc25a3c..58b36d1 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -182,6 +182,8 @@ struct psi_group psi_system = {
static void psi_avgs_work(struct work_struct *work);
+static void poll_timer_fn(struct timer_list *t);
+
static void group_init(struct psi_group *group)
{
int cpu;
@@ -201,6 +203,8 @@ static void group_init(struct psi_group *group)
memset(group->polling_total, 0, sizeof(group->polling_total));
group->polling_next_update = ULLONG_MAX;
group->polling_until = 0;
+ init_waitqueue_head(&group->poll_wait);
+ timer_setup(&group->poll_timer, poll_timer_fn, 0);
rcu_assign_pointer(group->poll_task, NULL);
}
@@ -1157,9 +1161,7 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group,
return ERR_CAST(task);
}
atomic_set(&group->poll_wakeup, 0);
- init_waitqueue_head(&group->poll_wait);
wake_up_process(task);
- timer_setup(&group->poll_timer, poll_timer_fn, 0);
rcu_assign_pointer(group->poll_task, task);
}
@@ -1211,6 +1213,7 @@ static void psi_trigger_destroy(struct kref *ref)
group->poll_task,
lockdep_is_held(&group->trigger_lock));
rcu_assign_pointer(group->poll_task, NULL);
+ del_timer(&group->poll_timer);
}
}
@@ -1223,17 +1226,14 @@ static void psi_trigger_destroy(struct kref *ref)
*/
synchronize_rcu();
/*
- * Destroy the kworker after releasing trigger_lock to prevent a
+ * Stop kthread 'psimon' after releasing trigger_lock to prevent a
* deadlock while waiting for psi_poll_work to acquire trigger_lock
*/
if (task_to_destroy) {
/*
* After the RCU grace period has expired, the worker
* can no longer be found through group->poll_task.
- * But it might have been already scheduled before
- * that - deschedule it cleanly before destroying it.
*/
- del_timer_sync(&group->poll_timer);
kthread_stop(task_to_destroy);
}
kfree(t);
prev parent reply other threads:[~2021-06-24 7:39 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1623371374-15664-1-git-send-email-huangzhaoyang@gmail.com>
2021-06-11 0:37 ` [Resend PATCH v6] psi: fix race between psi_trigger_create/destroy Zhaoyang Huang
2021-06-11 6:58 ` Peter Zijlstra
2021-06-24 7:39 ` tip-bot2 for Zhaoyang Huang [this message]
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