From: Huangzhaoyang <huangzhaoyang@gmail.com>
To: Johannes Weiner <hannes@cmpxchg.org>,
Suren Baghdasaryan <surenb@google.com>,
Zhaoyang Huang <zhaoyang.huang@unisoc.com>,
Ziwei Dai <ziwei.dai@unisoc.com>, Ke Wang <ke.wang@unisoc.com>,
linux-kernel@vger.kernel.org
Cc: Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Daniel Bristot de Oliveira <bristot@redhat.com>
Subject: [PATCH v6] psi: fix race between psi_trigger_create/destroy
Date: Fri, 21 May 2021 10:05:54 +0800 [thread overview]
Message-ID: <1621562754-8158-1-git-send-email-huangzhaoyang@gmail.com> (raw)
From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
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")
Signed-off-by: ziwei.dai <ziwei.dai@unisoc.com>
Signed-off-by: ke.wang <ke.wang@unisoc.com>
Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
---
v2: change del_timer_sync to del_timer in psi_trigger_destroy
v3: remove timer_setup within psi_tirgger_create
protect del_timer by extending the critical section of mutex_lock
v4: amend fix information on comment
v5: delete the poll_timer while assigning the task to NULL
v6: update subject and comments as Suren's suggestion
---
---
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);
--
1.9.1
next reply other threads:[~2021-05-21 2:07 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-21 2:05 Huangzhaoyang [this message]
2021-05-21 2:11 ` [PATCH v6] psi: fix race between psi_trigger_create/destroy Suren Baghdasaryan
2021-05-21 11:10 ` Peter Zijlstra
2021-05-21 14:18 ` Johannes Weiner
2021-06-10 7:31 ` Peter Zijlstra
2021-06-10 7:32 ` Peter Zijlstra
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1621562754-8158-1-git-send-email-huangzhaoyang@gmail.com \
--to=huangzhaoyang@gmail.com \
--cc=bristot@redhat.com \
--cc=bsegall@google.com \
--cc=dietmar.eggemann@arm.com \
--cc=hannes@cmpxchg.org \
--cc=juri.lelli@redhat.com \
--cc=ke.wang@unisoc.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mgorman@suse.de \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=rostedt@goodmis.org \
--cc=surenb@google.com \
--cc=vincent.guittot@linaro.org \
--cc=zhaoyang.huang@unisoc.com \
--cc=ziwei.dai@unisoc.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).