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SubjectRe: [PATCH 5/6] Lets ss->can_attach and ss->attach do whole threadgroups at a time
09:51, Ben Blum wrote:
> Lets ss->can_attach and ss->attach do whole threadgroups at a time
>
> This patch alters the ss->can_attach and ss->attach functions to be able to
> deal with a whole threadgroup at a time, for use in cgroup_attach_proc. (This
> is a pre-patch to cgroup-procs-writable.patch.)
>
> Currently, new mode of the attach function can only tell the subsystem about
> the old cgroup of the threadgroup leader. No subsystem currently needs that
> information for each thread that's being moved, but if one were to be added
> (for example, one that counts tasks within a group) this bit would need to be
> reworked a bit to tell the subsystem the right information.
>
> Signed-off-by: Ben Blum <bblum@google.com>
>
> ---
>
> include/linux/cgroup.h | 7 +++--
> kernel/cgroup.c | 4 +--
> kernel/cgroup_freezer.c | 15 +++++++++--
> kernel/cpuset.c | 65 ++++++++++++++++++++++++++++++++++++----------
> kernel/ns_cgroup.c | 16 ++++++++++-
> kernel/sched.c | 37 ++++++++++++++++++++++++--
> mm/memcontrol.c | 3 +-
> security/device_cgroup.c | 3 +-
> 8 files changed, 122 insertions(+), 28 deletions(-)
>
> diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
> index 24e3f1a..8286758 100644
> --- a/include/linux/cgroup.h
> +++ b/include/linux/cgroup.h
> @@ -408,10 +408,11 @@ struct cgroup_subsys {
> struct cgroup *cgrp);
> int (*pre_destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp);
> void (*destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp);
> - int (*can_attach)(struct cgroup_subsys *ss,
> - struct cgroup *cgrp, struct task_struct *tsk);
> + int (*can_attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
> + struct task_struct *tsk, bool threadgroup);
> void (*attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
> - struct cgroup *old_cgrp, struct task_struct *tsk);
> + struct cgroup *old_cgrp, struct task_struct *tsk,
> + bool threadgroup);

Could you also update Documentation/cgroups/cgroups.txt?

> void (*fork)(struct cgroup_subsys *ss, struct task_struct *task);
> void (*exit)(struct cgroup_subsys *ss, struct task_struct *task);
> int (*populate)(struct cgroup_subsys *ss,
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index a12bc8e..ea05d6b 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -1324,7 +1324,7 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
>
> for_each_subsys(root, ss) {
> if (ss->can_attach) {
> - retval = ss->can_attach(ss, cgrp, tsk);
> + retval = ss->can_attach(ss, cgrp, tsk, false);
> if (retval)
> return retval;
> }
> @@ -1362,7 +1362,7 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
>
> for_each_subsys(root, ss) {
> if (ss->attach)
> - ss->attach(ss, cgrp, oldcgrp, tsk);
> + ss->attach(ss, cgrp, oldcgrp, tsk, false);
> }
> set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
> synchronize_rcu();
> diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
> index fb249e2..4e352ab 100644
> --- a/kernel/cgroup_freezer.c
> +++ b/kernel/cgroup_freezer.c
> @@ -159,10 +159,9 @@ static bool is_task_frozen_enough(struct task_struct *task)
> */
> static int freezer_can_attach(struct cgroup_subsys *ss,
> struct cgroup *new_cgroup,
> - struct task_struct *task)
> + struct task_struct *task, bool threadgroup)
> {
> struct freezer *freezer;
> -

Please reserve this blank line.

> /*
> * Anything frozen can't move or be moved to/from.
> *
> @@ -177,6 +176,18 @@ static int freezer_can_attach(struct cgroup_subsys *ss,
> if (freezer->state == CGROUP_FROZEN)
> return -EBUSY;
>
> + if (threadgroup) {
> + struct task_struct *c;

And better have a blank line here. ;)

> + rcu_read_lock();
> + list_for_each_entry_rcu(c, &task->thread_group, thread_group) {
> + if (is_task_frozen_enough(c)) {
> + rcu_read_unlock();
> + return -EBUSY;
> + }
> + }
> + rcu_read_unlock();
> + }
> +
> return 0;
> }
>
> diff --git a/kernel/cpuset.c b/kernel/cpuset.c
> index 7e75a41..86397f4 100644
> --- a/kernel/cpuset.c
> +++ b/kernel/cpuset.c
> @@ -1324,9 +1324,10 @@ static int fmeter_getrate(struct fmeter *fmp)
> static cpumask_var_t cpus_attach;
>
> /* Called by cgroups to determine if a cpuset is usable; cgroup_mutex held */
> -static int cpuset_can_attach(struct cgroup_subsys *ss,
> - struct cgroup *cont, struct task_struct *tsk)
> +static int cpuset_can_attach(struct cgroup_subsys *ss, struct cgroup *cont,
> + struct task_struct *tsk, bool threadgroup)
> {
> + int ret;
> struct cpuset *cs = cgroup_cs(cont);
>
> if (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed))
> @@ -1343,18 +1344,50 @@ static int cpuset_can_attach(struct cgroup_subsys *ss,
> if (tsk->flags & PF_THREAD_BOUND)
> return -EINVAL;
>
> - return security_task_setscheduler(tsk, 0, NULL);
> + ret = security_task_setscheduler(tsk, 0, NULL);
> + if (ret)
> + return ret;
> + if (threadgroup) {
> + struct task_struct *c;

ditto

> + rcu_read_lock();
> + list_for_each_entry_rcu(c, &tsk->thread_group, thread_group) {
> + ret = security_task_setscheduler(c, 0, NULL);
> + if (ret) {
> + rcu_read_unlock();
> + return ret;
> + }
> + }
> + rcu_read_unlock();
> + }
> + return 0;
> +}



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