RE: [PATCH V2] cgroup: Introduce cgroup_detach_task().
Maybe your point can be added to the README or FAQ for cgroup. Try to shoot a patch for that, it will be more effective... Thanks, Xun -Original Message- From: cgroups-ow...@vger.kernel.org [mailto:cgroups-ow...@vger.kernel.org] On Behalf Of Dongsheng Yang Sent: Tuesday, August 26, 2014 10:16 AM To: Li Zefan Cc: Tejun Heo; Dongsheng Yang; cgro...@vger.kernel.org; linux-kernel@vger.kernel.org Subject: Re: [PATCH V2] cgroup: Introduce cgroup_detach_task(). On Tue, Aug 26, 2014 at 9:35 AM, Li Zefan wrote: > On 2014/8/25 23:00, Dongsheng Yang wrote: >> On Mon, Aug 25, 2014 at 10:47 PM, Tejun Heo wrote: >>> On Mon, Aug 25, 2014 at 10:46:03PM +0800, Dongsheng Yang wrote: >>>> My point here is that attaching and detaching are a pair of operations. >>> >>> There is no detaching from a cgroup. A task is always attached to a >>> cgroup whether that's a root or non-root cgroup. >> >> Okey, I should not think it as attaching and detaching. Just treat >> them as a move between root and non-root cgroup. >> >> It sounds reasonable to me now. >> > > I from time to time have to explain this to other people. Ha, we usually want to find a detach function when we saw a function named as cgroup_attach_task(). > -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH V2] cgroup: Introduce cgroup_detach_task().
On Tue, Aug 26, 2014 at 9:35 AM, Li Zefan wrote: > On 2014/8/25 23:00, Dongsheng Yang wrote: >> On Mon, Aug 25, 2014 at 10:47 PM, Tejun Heo wrote: >>> On Mon, Aug 25, 2014 at 10:46:03PM +0800, Dongsheng Yang wrote: My point here is that attaching and detaching are a pair of operations. >>> >>> There is no detaching from a cgroup. A task is always attached to a >>> cgroup whether that's a root or non-root cgroup. >> >> Okey, I should not think it as attaching and detaching. Just treat them as >> a move between root and non-root cgroup. >> >> It sounds reasonable to me now. >> > > I from time to time have to explain this to other people. Ha, we usually want to find a detach function when we saw a function named as cgroup_attach_task(). > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH V2] cgroup: Introduce cgroup_detach_task().
On 2014/8/25 23:00, Dongsheng Yang wrote: > On Mon, Aug 25, 2014 at 10:47 PM, Tejun Heo wrote: >> On Mon, Aug 25, 2014 at 10:46:03PM +0800, Dongsheng Yang wrote: >>> My point here is that attaching and detaching are a pair of operations. >> >> There is no detaching from a cgroup. A task is always attached to a >> cgroup whether that's a root or non-root cgroup. > > Okey, I should not think it as attaching and detaching. Just treat them as > a move between root and non-root cgroup. > > It sounds reasonable to me now. > I from time to time have to explain this to other people. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH V2] cgroup: Introduce cgroup_detach_task().
On Mon, Aug 25, 2014 at 10:47 PM, Tejun Heo wrote: > On Mon, Aug 25, 2014 at 10:46:03PM +0800, Dongsheng Yang wrote: >> My point here is that attaching and detaching are a pair of operations. > > There is no detaching from a cgroup. A task is always attached to a > cgroup whether that's a root or non-root cgroup. Okey, I should not think it as attaching and detaching. Just treat them as a move between root and non-root cgroup. It sounds reasonable to me now. Thanx. > > Thanks. > > -- > tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH V2] cgroup: Introduce cgroup_detach_task().
On Mon, Aug 25, 2014 at 10:46:03PM +0800, Dongsheng Yang wrote: > My point here is that attaching and detaching are a pair of operations. There is no detaching from a cgroup. A task is always attached to a cgroup whether that's a root or non-root cgroup. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH V2] cgroup: Introduce cgroup_detach_task().
Hi tj. On Mon, Aug 25, 2014 at 10:12 PM, Tejun Heo wrote: > On Mon, Aug 25, 2014 at 07:32:10PM +0800, Dongsheng Yang wrote: >> Currently, the only method to detach a task from a cgroup is moving >> it to others. It looks not natrual to me. > > Ummm... how is this different from moving it to the root cgroup? > "just because" usually isn't a good enough rationale. > Thanx for your reply :). My point here is that attaching and detaching are a pair of operations. And the things involved in these operations should be a process and a cgroup. But currently, when we want to detach a process from a cgroup (A), we have to attach it to another cgroup (B). I think it is not easy to understand. People would say: "Why I want to detach a process from A, I have to care about another cgroup." So I created this patch here wanting to make these operations more easy to understand. And make attaching and detaching to be antonymous in action. I think maybe we can use it in the Cgroup V2 which is in developing. :) That's all my reason for this patch. But you could think it makes no sense. It's okey to me. Thanx > Thanks. > > -- > tejun > -- > To unsubscribe from this list: send the line "unsubscribe cgroups" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH V2] cgroup: Introduce cgroup_detach_task().
On Mon, Aug 25, 2014 at 07:32:10PM +0800, Dongsheng Yang wrote: > Currently, the only method to detach a task from a cgroup is moving > it to others. It looks not natrual to me. Ummm... how is this different from moving it to the root cgroup? "just because" usually isn't a good enough rationale. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH V2] cgroup: Introduce cgroup_detach_task().
Currently, the only method to detach a task from a cgroup is moving
it to others. It looks not natrual to me.
Inspired by cgroup_subtree_control_write(), this patch introduce allow
user to at-detach a process to/from a cgroup by echo "+/-pid" to
cgroup.procs. In addition, we keep the old method to allow user
echo "pid" without "+/-" to cgroup.procs as a attaching behavior.
Signed-off-by: Dongsheng Yang
---
>From v1:
*Sorry for a incorrect comment in v1.
kernel/cgroup.c | 61 +++--
1 file changed, 59 insertions(+), 2 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 7dc8788..a4bb604 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2348,6 +2348,43 @@ static int cgroup_attach_task(struct cgroup *dst_cgrp,
return ret;
}
+/**
+ * cgroup_detach_task - detach a task or a whole threadgroup to a cgroup
+ * @src_cgrp: the cgroup to detach from
+ * @leader: the task or the leader of the threadgroup to be attached
+ * @threadgroup: attach the whole threadgroup?
+ *
+ * Call holding cgroup_mutex and threadgroup_lock of @leader.
+ */
+static int cgroup_detach_task(struct cgroup *src_cgrp __maybe_unused,
+ struct task_struct *leader, bool threadgroup)
+{
+ LIST_HEAD(preloaded_csets);
+ struct task_struct *task;
+ int ret;
+
+ /* look up all src csets */
+ down_read(_set_rwsem);
+ rcu_read_lock();
+ task = leader;
+ do {
+ cgroup_migrate_add_src(task_css_set(task), _dfl_root.cgrp,
+ _csets);
+ if (!threadgroup)
+ break;
+ } while_each_thread(leader, task);
+ rcu_read_unlock();
+ up_read(_set_rwsem);
+
+ /* prepare dst csets and commit */
+ ret = cgroup_migrate_prepare_dst(_dfl_root.cgrp, _csets);
+ if (!ret)
+ ret = cgroup_migrate(_dfl_root.cgrp, leader, threadgroup);
+
+ cgroup_migrate_finish(_csets);
+ return ret;
+}
+
/*
* Find the task_struct of the task to attach by vpid and pass it along to the
* function to attach either it or all tasks in its threadgroup. Will lock
@@ -2361,8 +2398,25 @@ static ssize_t __cgroup_procs_write(struct
kernfs_open_file *of, char *buf,
struct cgroup *cgrp;
pid_t pid;
int ret;
+ bool attach;
- if (kstrtoint(strstrip(buf), 0, ) || pid < 0)
+ /*
+* Parse input - pid prefixed with either + or -.
+*/
+ buf = strstrip(buf);
+ if (*buf == '+') {
+ attach = true;
+ buf++;
+ } else if (*buf == '-') {
+ attach = false;
+ buf++;
+ } else {
+ if (!isdigit(*buf))
+ return -EINVAL;
+ attach = true;
+ }
+
+ if (kstrtoint(buf, 0, ) || pid < 0)
return -EINVAL;
cgrp = cgroup_kn_lock_live(of->kn);
@@ -2426,7 +2480,10 @@ retry_find_task:
}
}
- ret = cgroup_attach_task(cgrp, tsk, threadgroup);
+ if (attach)
+ ret = cgroup_attach_task(cgrp, tsk, threadgroup);
+ else
+ ret = cgroup_detach_task(cgrp, tsk, threadgroup);
threadgroup_unlock(tsk);
--
1.8.4.2
--
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More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[PATCH V2] cgroup: Introduce cgroup_detach_task().
Currently, the only method to detach a task from a cgroup is moving
it to others. It looks not natrual to me.
Inspired by cgroup_subtree_control_write(), this patch introduce allow
user to at-detach a process to/from a cgroup by echo +/-pid to
cgroup.procs. In addition, we keep the old method to allow user
echo pid without +/- to cgroup.procs as a attaching behavior.
Signed-off-by: Dongsheng Yang yangds.f...@cn.fujitsu.com
---
From v1:
*Sorry for a incorrect comment in v1.
kernel/cgroup.c | 61 +++--
1 file changed, 59 insertions(+), 2 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 7dc8788..a4bb604 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2348,6 +2348,43 @@ static int cgroup_attach_task(struct cgroup *dst_cgrp,
return ret;
}
+/**
+ * cgroup_detach_task - detach a task or a whole threadgroup to a cgroup
+ * @src_cgrp: the cgroup to detach from
+ * @leader: the task or the leader of the threadgroup to be attached
+ * @threadgroup: attach the whole threadgroup?
+ *
+ * Call holding cgroup_mutex and threadgroup_lock of @leader.
+ */
+static int cgroup_detach_task(struct cgroup *src_cgrp __maybe_unused,
+ struct task_struct *leader, bool threadgroup)
+{
+ LIST_HEAD(preloaded_csets);
+ struct task_struct *task;
+ int ret;
+
+ /* look up all src csets */
+ down_read(css_set_rwsem);
+ rcu_read_lock();
+ task = leader;
+ do {
+ cgroup_migrate_add_src(task_css_set(task), cgrp_dfl_root.cgrp,
+ preloaded_csets);
+ if (!threadgroup)
+ break;
+ } while_each_thread(leader, task);
+ rcu_read_unlock();
+ up_read(css_set_rwsem);
+
+ /* prepare dst csets and commit */
+ ret = cgroup_migrate_prepare_dst(cgrp_dfl_root.cgrp, preloaded_csets);
+ if (!ret)
+ ret = cgroup_migrate(cgrp_dfl_root.cgrp, leader, threadgroup);
+
+ cgroup_migrate_finish(preloaded_csets);
+ return ret;
+}
+
/*
* Find the task_struct of the task to attach by vpid and pass it along to the
* function to attach either it or all tasks in its threadgroup. Will lock
@@ -2361,8 +2398,25 @@ static ssize_t __cgroup_procs_write(struct
kernfs_open_file *of, char *buf,
struct cgroup *cgrp;
pid_t pid;
int ret;
+ bool attach;
- if (kstrtoint(strstrip(buf), 0, pid) || pid 0)
+ /*
+* Parse input - pid prefixed with either + or -.
+*/
+ buf = strstrip(buf);
+ if (*buf == '+') {
+ attach = true;
+ buf++;
+ } else if (*buf == '-') {
+ attach = false;
+ buf++;
+ } else {
+ if (!isdigit(*buf))
+ return -EINVAL;
+ attach = true;
+ }
+
+ if (kstrtoint(buf, 0, pid) || pid 0)
return -EINVAL;
cgrp = cgroup_kn_lock_live(of-kn);
@@ -2426,7 +2480,10 @@ retry_find_task:
}
}
- ret = cgroup_attach_task(cgrp, tsk, threadgroup);
+ if (attach)
+ ret = cgroup_attach_task(cgrp, tsk, threadgroup);
+ else
+ ret = cgroup_detach_task(cgrp, tsk, threadgroup);
threadgroup_unlock(tsk);
--
1.8.4.2
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH V2] cgroup: Introduce cgroup_detach_task().
On Mon, Aug 25, 2014 at 07:32:10PM +0800, Dongsheng Yang wrote: Currently, the only method to detach a task from a cgroup is moving it to others. It looks not natrual to me. Ummm... how is this different from moving it to the root cgroup? just because usually isn't a good enough rationale. Thanks. -- tejun -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH V2] cgroup: Introduce cgroup_detach_task().
Hi tj. On Mon, Aug 25, 2014 at 10:12 PM, Tejun Heo t...@kernel.org wrote: On Mon, Aug 25, 2014 at 07:32:10PM +0800, Dongsheng Yang wrote: Currently, the only method to detach a task from a cgroup is moving it to others. It looks not natrual to me. Ummm... how is this different from moving it to the root cgroup? just because usually isn't a good enough rationale. Thanx for your reply :). My point here is that attaching and detaching are a pair of operations. And the things involved in these operations should be a process and a cgroup. But currently, when we want to detach a process from a cgroup (A), we have to attach it to another cgroup (B). I think it is not easy to understand. People would say: Why I want to detach a process from A, I have to care about another cgroup. So I created this patch here wanting to make these operations more easy to understand. And make attaching and detaching to be antonymous in action. I think maybe we can use it in the Cgroup V2 which is in developing. :) That's all my reason for this patch. But you could think it makes no sense. It's okey to me. Thanx Thanks. -- tejun -- To unsubscribe from this list: send the line unsubscribe cgroups in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH V2] cgroup: Introduce cgroup_detach_task().
On Mon, Aug 25, 2014 at 10:46:03PM +0800, Dongsheng Yang wrote: My point here is that attaching and detaching are a pair of operations. There is no detaching from a cgroup. A task is always attached to a cgroup whether that's a root or non-root cgroup. Thanks. -- tejun -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH V2] cgroup: Introduce cgroup_detach_task().
On Mon, Aug 25, 2014 at 10:47 PM, Tejun Heo t...@kernel.org wrote: On Mon, Aug 25, 2014 at 10:46:03PM +0800, Dongsheng Yang wrote: My point here is that attaching and detaching are a pair of operations. There is no detaching from a cgroup. A task is always attached to a cgroup whether that's a root or non-root cgroup. Okey, I should not think it as attaching and detaching. Just treat them as a move between root and non-root cgroup. It sounds reasonable to me now. Thanx. Thanks. -- tejun -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH V2] cgroup: Introduce cgroup_detach_task().
On 2014/8/25 23:00, Dongsheng Yang wrote: On Mon, Aug 25, 2014 at 10:47 PM, Tejun Heo t...@kernel.org wrote: On Mon, Aug 25, 2014 at 10:46:03PM +0800, Dongsheng Yang wrote: My point here is that attaching and detaching are a pair of operations. There is no detaching from a cgroup. A task is always attached to a cgroup whether that's a root or non-root cgroup. Okey, I should not think it as attaching and detaching. Just treat them as a move between root and non-root cgroup. It sounds reasonable to me now. I from time to time have to explain this to other people. -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH V2] cgroup: Introduce cgroup_detach_task().
On Tue, Aug 26, 2014 at 9:35 AM, Li Zefan lize...@huawei.com wrote: On 2014/8/25 23:00, Dongsheng Yang wrote: On Mon, Aug 25, 2014 at 10:47 PM, Tejun Heo t...@kernel.org wrote: On Mon, Aug 25, 2014 at 10:46:03PM +0800, Dongsheng Yang wrote: My point here is that attaching and detaching are a pair of operations. There is no detaching from a cgroup. A task is always attached to a cgroup whether that's a root or non-root cgroup. Okey, I should not think it as attaching and detaching. Just treat them as a move between root and non-root cgroup. It sounds reasonable to me now. I from time to time have to explain this to other people. Ha, we usually want to find a detach function when we saw a function named as cgroup_attach_task(). -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
RE: [PATCH V2] cgroup: Introduce cgroup_detach_task().
Maybe your point can be added to the README or FAQ for cgroup. Try to shoot a patch for that, it will be more effective... Thanks, Xun -Original Message- From: cgroups-ow...@vger.kernel.org [mailto:cgroups-ow...@vger.kernel.org] On Behalf Of Dongsheng Yang Sent: Tuesday, August 26, 2014 10:16 AM To: Li Zefan Cc: Tejun Heo; Dongsheng Yang; cgro...@vger.kernel.org; linux-kernel@vger.kernel.org Subject: Re: [PATCH V2] cgroup: Introduce cgroup_detach_task(). On Tue, Aug 26, 2014 at 9:35 AM, Li Zefan lize...@huawei.com wrote: On 2014/8/25 23:00, Dongsheng Yang wrote: On Mon, Aug 25, 2014 at 10:47 PM, Tejun Heo t...@kernel.org wrote: On Mon, Aug 25, 2014 at 10:46:03PM +0800, Dongsheng Yang wrote: My point here is that attaching and detaching are a pair of operations. There is no detaching from a cgroup. A task is always attached to a cgroup whether that's a root or non-root cgroup. Okey, I should not think it as attaching and detaching. Just treat them as a move between root and non-root cgroup. It sounds reasonable to me now. I from time to time have to explain this to other people. Ha, we usually want to find a detach function when we saw a function named as cgroup_attach_task(). -- To unsubscribe from this list: send the line unsubscribe cgroups in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
