From: Prateek Sood <prsood@codeaurora.org>
To: Tejun Heo <tj@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
avagin@gmail.com, mingo@kernel.org, linux-kernel@vger.kernel.org,
cgroups@vger.kernel.org, sramana@codeaurora.org
Subject: Re: [PATCH] cgroup/cpuset: fix circular locking dependency
Date: Fri, 15 Dec 2017 14:24:55 +0530 [thread overview]
Message-ID: <c282b638-95ef-b688-9249-f23a733c0a43@codeaurora.org> (raw)
In-Reply-To: <20171213154041.GP3919388@devbig577.frc2.facebook.com>
On 12/13/2017 09:10 PM, Tejun Heo wrote:
Hi TJ,
> Hello, Prateek.
>
> On Wed, Dec 13, 2017 at 07:58:24PM +0530, Prateek Sood wrote:
>> Did you mean something like below. If not then could you
>> please share a patch for this problem in
>> cgroup_transfer_tasks().
>
> Oh we surely can add a new iterator but we can just count in
> cgroup_transfer_tasks() too, right?
I did not get what you meant by this. Could you please share a
patch for this.
>
> Thanks.
>
Following are two ways to improve cgroup_transfer_tasks(). In
both cases task in PF_EXITING state would be left in source
cgroup. It would be removed from cgroup_exit() in exit path.
diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index 024085d..e2bdcdb 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -123,7 +123,10 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
*/
do {
css_task_iter_start(&from->self, 0, &it);
- task = css_task_iter_next(&it);
+ do {
+ task = css_task_iter_next(&it);
+ } while (task && (task & PF_EXITING))
+
if (task)
get_task_struct(task);
css_task_iter_end(&it);
----------------------------8<---------------------------------
diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index 024085d..843b8bb 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -121,12 +121,11 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
* Migrate tasks one-by-one until @from is empty. This fails iff
* ->can_attach() fails.
*/
+ css_task_iter_start(&from->self, 0, &it);
do {
- css_task_iter_start(&from->self, 0, &it);
task = css_task_iter_next(&it);
if (task)
get_task_struct(task);
- css_task_iter_end(&it);
if (task) {
ret = cgroup_migrate(task, false, &mgctx);
@@ -135,6 +134,7 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
put_task_struct(task);
}
} while (task && !ret);
+ css_task_iter_end(&it);
out_err:
cgroup_migrate_finish(&mgctx);
percpu_up_write(&cgroup_threadgroup_rwsem);
Thanks
--
Qualcomm India Private Limited, on behalf of Qualcomm Innovation
Center, Inc., is a member of Code Aurora Forum, a Linux Foundation
Collaborative Project
next prev parent reply other threads:[~2017-12-15 8:55 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CANaxB-zT+sz=z1FFk5npnwMySdfKCBZDkM+P+=JXDkCXbh=rCw@mail.gmail.com>
2017-11-28 11:35 ` [PATCH] cgroup/cpuset: fix circular locking dependency Prateek Sood
2017-12-04 5:14 ` Prateek Sood
2017-12-04 20:22 ` Tejun Heo
2017-12-04 22:58 ` Tejun Heo
2017-12-04 23:01 ` Peter Zijlstra
2017-12-08 9:40 ` Prateek Sood
2017-12-08 11:45 ` Prateek Sood
2017-12-11 15:32 ` Tejun Heo
2017-12-13 14:28 ` Prateek Sood
2017-12-13 15:40 ` Tejun Heo
2017-12-15 8:54 ` Prateek Sood [this message]
2017-12-15 13:22 ` Tejun Heo
2017-12-15 19:06 ` Prateek Sood
2017-12-19 7:26 ` [PATCH] cgroup: Fix deadlock in cpu hotplug path Prateek Sood
2017-12-19 13:39 ` Tejun Heo
2017-12-11 15:20 ` [PATCH] cgroup/cpuset: fix circular locking dependency Tejun Heo
2017-12-13 7:50 ` Prateek Sood
2017-12-13 16:06 ` Tejun Heo
2017-12-15 19:04 ` Prateek Sood
2017-12-28 20:37 ` Prateek Sood
2018-01-02 16:16 ` Tejun Heo
2018-01-02 17:44 ` Paul E. McKenney
2018-01-02 18:01 ` Paul E. McKenney
2018-01-08 12:28 ` Tejun Heo
2018-01-08 13:47 ` [PATCH wq/for-4.16 1/2] workqueue: separate out init_rescuer() Tejun Heo
2018-01-08 13:47 ` [PATCH wq/for-4.16 2/2] workqueue: allow WQ_MEM_RECLAIM on early init workqueues Tejun Heo
2018-01-08 22:52 ` [PATCH] cgroup/cpuset: fix circular locking dependency Paul E. McKenney
2018-01-09 0:31 ` Paul E. McKenney
2018-01-09 3:42 ` Tejun Heo
2018-01-09 4:20 ` Paul E. McKenney
2018-01-09 13:44 ` Tejun Heo
2018-01-09 15:21 ` Paul E. McKenney
2018-01-09 15:37 ` Tejun Heo
2018-01-09 16:00 ` Paul E. McKenney
2018-01-10 20:08 ` Paul E. McKenney
2018-01-10 21:41 ` Tejun Heo
2018-01-10 22:10 ` Paul E. McKenney
2018-01-15 12:02 ` Prateek Sood
2018-01-16 16:27 ` Tejun Heo
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