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
WARNING: multiple messages have this Message-ID (diff)
From: Prateek Sood <prsood-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org> To: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> Cc: Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>, avagin-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, sramana-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.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.GP3919388-4dN5La/x3IkLX0oZNxdnEQ2O0Ztt9esIQQ4Iyu8u01E@public.gmane.org> 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: 62+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-11-28 1:22 cgroup/for-next: WARNING: possible circular locking dependency detected in cpuset_write_resmask Andrei Vagin 2017-11-28 11:35 ` [PATCH] cgroup/cpuset: fix circular locking dependency Prateek Sood 2017-12-04 5:14 ` Prateek Sood 2017-12-04 5:14 ` Prateek Sood 2017-12-04 20:22 ` Tejun Heo 2017-12-04 20:22 ` Tejun Heo 2017-12-04 22:58 ` Tejun Heo 2017-12-04 23:01 ` Peter Zijlstra 2017-12-04 23:01 ` Peter Zijlstra 2017-12-08 9:40 ` Prateek Sood 2017-12-08 11:45 ` Prateek Sood 2017-12-08 11:45 ` Prateek Sood 2017-12-11 15:32 ` Tejun Heo 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 8:54 ` Prateek Sood 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 7:26 ` Prateek Sood 2017-12-19 13:39 ` Tejun Heo 2017-12-11 15:20 ` [PATCH] cgroup/cpuset: fix circular locking dependency Tejun Heo 2017-12-11 15:20 ` Tejun Heo 2017-12-13 7:50 ` Prateek Sood 2017-12-13 7:50 ` Prateek Sood 2017-12-13 16:06 ` Tejun Heo 2017-12-15 19:04 ` Prateek Sood 2017-12-15 19:04 ` Prateek Sood 2017-12-28 20:37 ` 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 17:44 ` Paul E. McKenney 2018-01-02 18:01 ` Paul E. McKenney 2018-01-08 12:28 ` Tejun Heo 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 ` 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 13:47 ` Tejun Heo 2018-01-08 22:52 ` [PATCH] cgroup/cpuset: fix circular locking dependency Paul E. McKenney 2018-01-08 22:52 ` Paul E. McKenney 2018-01-09 0:31 ` Paul E. McKenney 2018-01-09 3:42 ` Tejun Heo 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 15:21 ` Paul E. McKenney 2018-01-09 15:37 ` Tejun Heo 2018-01-09 16:00 ` Paul E. McKenney 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 21:41 ` Tejun Heo 2018-01-10 22:10 ` Paul E. McKenney 2018-01-10 22:10 ` Paul E. McKenney 2018-01-15 12:02 ` Prateek Sood 2018-01-15 12:02 ` Prateek Sood 2018-01-16 16:27 ` Tejun Heo
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