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Commit b77d7b60 authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: cgroup_css_from_dir() now should be called with RCU read locked 



cgroup->subsys[] will become RCU protected and thus all cgroup_css()
usages should either be under RCU read lock or cgroup_mutex.  This
patch updates cgroup_css_from_dir() which returns the matching
cgroup_subsys_state given a directory file and subsys_id so that it
requires RCU read lock and updates its sole user
perf_cgroup_connect().

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
parent 0ae78e0b

kernel/cgroup.c

+10 −2
Original line number Diff line number Diff line
@@ -5616,8 +5616,14 @@ struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id) 
}

EXPORT_SYMBOL_GPL(css_lookup);



/*

 * get corresponding css from file open on cgroupfs directory

/**

 * cgroup_css_from_dir - get corresponding css from file open on cgroup dir

 * @f: directory file of interest

 * @id: subsystem id of interest

 *

 * Must be called under RCU read lock.  The caller is responsible for

 * pinning the returned css if it needs to be accessed outside the RCU

 * critical section.

 */

struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id)

{
@@ -5625,6 +5631,8 @@ struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id) 
	struct inode *inode;

	struct cgroup_subsys_state *css;



	WARN_ON_ONCE(!rcu_read_lock_held());



	inode = file_inode(f);

	/* check in cgroup filesystem dir */

	if (inode->i_op != &cgroup_dir_inode_operations)

kernel/events/core.c

+3 −0
Original line number Diff line number Diff line
@@ -591,6 +591,8 @@ static inline int perf_cgroup_connect(int fd, struct perf_event *event, 
	if (!f.file)

		return -EBADF;



	rcu_read_lock();



	css = cgroup_css_from_dir(f.file, perf_subsys_id);

	if (IS_ERR(css)) {

		ret = PTR_ERR(css);
@@ -617,6 +619,7 @@ static inline int perf_cgroup_connect(int fd, struct perf_event *event, 
		ret = -EINVAL;

	}

out:

	rcu_read_unlock();

	fdput(f);

	return ret;

}