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Commit 4fc3e1cf authored by Olav Haugan's avatar Olav Haugan Committed by Vinayak Menon
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cgroup: add provision to move task to root cgroup 



In some cases we may need to a move task out its cgroup to avoid
priority inversion, when it is holding critical resources
required by other higher priority tasks. So add a mechanism to
move a task out of its cgroup to avoid the task being starved.

CRs-Fixed: 983539
Change-Id: I167d7f965d133ec996bd13f57183468e8399bacc
Signed-off-by: default avatarOlav Haugan <ohaugan@codeaurora.org>
Signed-off-by: default avatarVinayak Menon <vinmenon@codeaurora.org>
parent 53d1dd96

include/linux/cgroup.h

+6 −0
Original line number Diff line number Diff line
@@ -912,6 +912,7 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from); 


struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,

						       struct cgroup_subsys *ss);

int cgroup_attach_task_to_root(struct task_struct *tsk, int wait);



/*

 * Default Android check for whether the current process is allowed to move a
@@ -950,6 +951,11 @@ static inline int subsys_cgroup_allow_attach(struct cgroup_subsys_state *css, 
{

	return -EINVAL;

}



static inline int cgroup_attach_task_to_root(struct task_struct *tsk, int wait)

{

	return 0;

}

#endif /* !CONFIG_CGROUPS */



#endif /* _LINUX_CGROUP_H */

kernel/cgroup.c

+52 −0
Original line number Diff line number Diff line
@@ -2505,6 +2505,58 @@ static ssize_t cgroup_tasks_write(struct kernfs_open_file *of, 
	return __cgroup_procs_write(of, buf, nbytes, off, false);

}



#ifdef CONFIG_CGROUP_SCHED

int cgroup_attach_task_to_root(struct task_struct *tsk, int wait)

{

	int ret = 0;

	struct cgroup *cgrp;

	struct cgroup *root_cgrp = NULL;



	if (!mutex_trylock(&cgroup_mutex)) {

		/*This can be a case of recursion, so bail out */

		if (!wait)

			return -EBUSY;

		mutex_lock(&cgroup_mutex);

	}



	cgrp = task_cgroup(tsk, cpu_cgrp_id);



	if (cgrp && cgrp->root)

		root_cgrp = &cgrp->root->cgrp;



	if (root_cgrp && cgrp != root_cgrp)

		cgrp = root_cgrp;

	else

		goto out_unlock_cgroup;



	if (cgroup_is_dead(cgrp)) {

		ret = -ENODEV;

		goto out_unlock_cgroup;

	}



	rcu_read_lock();



	get_task_struct(tsk);

	rcu_read_unlock();



	threadgroup_lock(tsk);



	ret = cgroup_attach_task(cgrp, tsk, false);



	threadgroup_unlock(tsk);



	put_task_struct(tsk);

out_unlock_cgroup:

	mutex_unlock(&cgroup_mutex);

	return ret;

}

#else

int cgroup_attach_task_to_root(struct task_struct *tsk, int wait)

{

	return 0;

}

#endif



static ssize_t cgroup_procs_write(struct kernfs_open_file *of,

				  char *buf, size_t nbytes, loff_t off)

{