Commit afcf6c8b authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: add cgroup_subsys->free() method and use it to fix pids controller 



pids controller is completely broken in that it uncharges when a task
exits allowing zombies to escape resource control.  With the recent
updates, cgroup core now maintains cgroup association till task free
and pids controller can be fixed by uncharging on free instead of
exit.

This patch adds cgroup_subsys->free() method and update pids
controller to use it instead of ->exit() for uncharging.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: Aleksa Sarai <cyphar@cyphar.com>
parent 2e91fa7f

Documentation/cgroups/cgroups.txt

+4 −0
Original line number Diff line number Diff line
@@ -637,6 +637,10 @@ void exit(struct task_struct *task) 


Called during task exit.



void free(struct task_struct *task)



Called when the task_struct is freed.



void bind(struct cgroup *root)

(cgroup_mutex held by caller)

include/linux/cgroup-defs.h

+1 −0
Original line number Diff line number Diff line
@@ -436,6 +436,7 @@ struct cgroup_subsys { 
	void (*cancel_fork)(struct task_struct *task, void *priv);

	void (*fork)(struct task_struct *task, void *priv);

	void (*exit)(struct task_struct *task);

	void (*free)(struct task_struct *task);

	void (*bind)(struct cgroup_subsys_state *root_css);



	int early_init;

kernel/cgroup.c

+7 −0
Original line number Diff line number Diff line
@@ -206,6 +206,7 @@ static u64 css_serial_nr_next = 1; 
 */

static unsigned long have_fork_callback __read_mostly;

static unsigned long have_exit_callback __read_mostly;

static unsigned long have_free_callback __read_mostly;



/* Ditto for the can_fork callback. */

static unsigned long have_canfork_callback __read_mostly;
@@ -5180,6 +5181,7 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early) 


	have_fork_callback |= (bool)ss->fork << ss->id;

	have_exit_callback |= (bool)ss->exit << ss->id;

	have_free_callback |= (bool)ss->free << ss->id;

	have_canfork_callback |= (bool)ss->can_fork << ss->id;



	/* At system boot, before all subsystems have been
@@ -5637,6 +5639,11 @@ void cgroup_exit(struct task_struct *tsk) 
void cgroup_free(struct task_struct *task)

{

	struct css_set *cset = task_css_set(task);

	struct cgroup_subsys *ss;

	int ssid;



	for_each_subsys_which(ss, ssid, &have_free_callback)

		ss->free(task);



	put_css_set(cset);

}

kernel/cgroup_pids.c

+2 −2
Original line number Diff line number Diff line
@@ -266,7 +266,7 @@ static void pids_fork(struct task_struct *task, void *priv) 
	css_put(old_css);

}



static void pids_exit(struct task_struct *task)

static void pids_free(struct task_struct *task)

{

	struct pids_cgroup *pids = css_pids(task_css(task, pids_cgrp_id));
@@ -347,7 +347,7 @@ struct cgroup_subsys pids_cgrp_subsys = { 
	.can_fork	= pids_can_fork,

	.cancel_fork	= pids_cancel_fork,

	.fork		= pids_fork,

	.exit		= pids_exit,

	.free		= pids_free,

	.legacy_cftypes	= pids_files,

	.dfl_cftypes	= pids_files,

};

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