Commit b94f9ac7 authored by Waiman Long's avatar Waiman Long Committed by Tejun Heo
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cgroup/cpuset: Change references of cpuset_mutex to cpuset_rwsem 



Since commit 1243dc51 ("cgroup/cpuset: Convert cpuset_mutex to
percpu_rwsem"), cpuset_mutex has been replaced by cpuset_rwsem which is
a percpu rwsem. However, the comments in kernel/cgroup/cpuset.c still
reference cpuset_mutex which are now incorrect.

Change all the references of cpuset_mutex to cpuset_rwsem.

Fixes: 1243dc51 ("cgroup/cpuset: Convert cpuset_mutex to percpu_rwsem")
Signed-off-by: default avatarWaiman Long <longman@redhat.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 22b12557

kernel/cgroup/cpuset.c

+29 −27
Original line number Diff line number Diff line
@@ -311,17 +311,19 @@ static struct cpuset top_cpuset = { 
		if (is_cpuset_online(((des_cs) = css_cs((pos_css)))))



/*

 * There are two global locks guarding cpuset structures - cpuset_mutex and

 * There are two global locks guarding cpuset structures - cpuset_rwsem and

 * callback_lock. We also require taking task_lock() when dereferencing a

 * task's cpuset pointer. See "The task_lock() exception", at the end of this

 * comment.

 * comment.  The cpuset code uses only cpuset_rwsem write lock.  Other

 * kernel subsystems can use cpuset_read_lock()/cpuset_read_unlock() to

 * prevent change to cpuset structures.

 *

 * A task must hold both locks to modify cpusets.  If a task holds

 * cpuset_mutex, then it blocks others wanting that mutex, ensuring that it

 * cpuset_rwsem, it blocks others wanting that rwsem, ensuring that it

 * is the only task able to also acquire callback_lock and be able to

 * modify cpusets.  It can perform various checks on the cpuset structure

 * first, knowing nothing will change.  It can also allocate memory while

 * just holding cpuset_mutex.  While it is performing these checks, various

 * just holding cpuset_rwsem.  While it is performing these checks, various

 * callback routines can briefly acquire callback_lock to query cpusets.

 * Once it is ready to make the changes, it takes callback_lock, blocking

 * everyone else.
@@ -393,7 +395,7 @@ static inline bool is_in_v2_mode(void) 
 * One way or another, we guarantee to return some non-empty subset

 * of cpu_online_mask.

 *

 * Call with callback_lock or cpuset_mutex held.

 * Call with callback_lock or cpuset_rwsem held.

 */

static void guarantee_online_cpus(struct task_struct *tsk,

				  struct cpumask *pmask)
@@ -435,7 +437,7 @@ static void guarantee_online_cpus(struct task_struct *tsk, 
 * One way or another, we guarantee to return some non-empty subset

 * of node_states[N_MEMORY].

 *

 * Call with callback_lock or cpuset_mutex held.

 * Call with callback_lock or cpuset_rwsem held.

 */

static void guarantee_online_mems(struct cpuset *cs, nodemask_t *pmask)

{
@@ -447,7 +449,7 @@ static void guarantee_online_mems(struct cpuset *cs, nodemask_t *pmask) 
/*

 * update task's spread flag if cpuset's page/slab spread flag is set

 *

 * Call with callback_lock or cpuset_mutex held.

 * Call with callback_lock or cpuset_rwsem held.

 */

static void cpuset_update_task_spread_flag(struct cpuset *cs,

					struct task_struct *tsk)
@@ -468,7 +470,7 @@ static void cpuset_update_task_spread_flag(struct cpuset *cs, 
 *

 * One cpuset is a subset of another if all its allowed CPUs and

 * Memory Nodes are a subset of the other, and its exclusive flags

 * are only set if the other's are set.  Call holding cpuset_mutex.

 * are only set if the other's are set.  Call holding cpuset_rwsem.

 */



static int is_cpuset_subset(const struct cpuset *p, const struct cpuset *q)
@@ -577,7 +579,7 @@ static inline void free_cpuset(struct cpuset *cs) 
 * If we replaced the flag and mask values of the current cpuset

 * (cur) with those values in the trial cpuset (trial), would

 * our various subset and exclusive rules still be valid?  Presumes

 * cpuset_mutex held.

 * cpuset_rwsem held.

 *

 * 'cur' is the address of an actual, in-use cpuset.  Operations

 * such as list traversal that depend on the actual address of the
@@ -700,7 +702,7 @@ static void update_domain_attr_tree(struct sched_domain_attr *dattr, 
	rcu_read_unlock();

}



/* Must be called with cpuset_mutex held.  */

/* Must be called with cpuset_rwsem held.  */

static inline int nr_cpusets(void)

{

	/* jump label reference count + the top-level cpuset */
@@ -726,7 +728,7 @@ static inline int nr_cpusets(void) 
 * domains when operating in the severe memory shortage situations

 * that could cause allocation failures below.

 *

 * Must be called with cpuset_mutex held.

 * Must be called with cpuset_rwsem held.

 *

 * The three key local variables below are:

 *    cp - cpuset pointer, used (together with pos_css) to perform a
@@ -1005,7 +1007,7 @@ partition_and_rebuild_sched_domains(int ndoms_new, cpumask_var_t doms_new[], 
 * 'cpus' is removed, then call this routine to rebuild the

 * scheduler's dynamic sched domains.

 *

 * Call with cpuset_mutex held.  Takes cpus_read_lock().

 * Call with cpuset_rwsem held.  Takes cpus_read_lock().

 */

static void rebuild_sched_domains_locked(void)

{
@@ -1078,7 +1080,7 @@ void rebuild_sched_domains(void) 
 * @cs: the cpuset in which each task's cpus_allowed mask needs to be changed

 *

 * Iterate through each task of @cs updating its cpus_allowed to the

 * effective cpuset's.  As this function is called with cpuset_mutex held,

 * effective cpuset's.  As this function is called with cpuset_rwsem held,

 * cpuset membership stays stable.

 */

static void update_tasks_cpumask(struct cpuset *cs)
@@ -1347,7 +1349,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd, 
 *

 * On legacy hierarchy, effective_cpus will be the same with cpu_allowed.

 *

 * Called with cpuset_mutex held

 * Called with cpuset_rwsem held

 */

static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)

{
@@ -1704,12 +1706,12 @@ static void *cpuset_being_rebound; 
 * @cs: the cpuset in which each task's mems_allowed mask needs to be changed

 *

 * Iterate through each task of @cs updating its mems_allowed to the

 * effective cpuset's.  As this function is called with cpuset_mutex held,

 * effective cpuset's.  As this function is called with cpuset_rwsem held,

 * cpuset membership stays stable.

 */

static void update_tasks_nodemask(struct cpuset *cs)

{

	static nodemask_t newmems;	/* protected by cpuset_mutex */

	static nodemask_t newmems;	/* protected by cpuset_rwsem */

	struct css_task_iter it;

	struct task_struct *task;
@@ -1722,7 +1724,7 @@ static void update_tasks_nodemask(struct cpuset *cs) 
	 * take while holding tasklist_lock.  Forks can happen - the

	 * mpol_dup() cpuset_being_rebound check will catch such forks,

	 * and rebind their vma mempolicies too.  Because we still hold

	 * the global cpuset_mutex, we know that no other rebind effort

	 * the global cpuset_rwsem, we know that no other rebind effort

	 * will be contending for the global variable cpuset_being_rebound.

	 * It's ok if we rebind the same mm twice; mpol_rebind_mm()

	 * is idempotent.  Also migrate pages in each mm to new nodes.
@@ -1768,7 +1770,7 @@ static void update_tasks_nodemask(struct cpuset *cs) 
 *

 * On legacy hierarchy, effective_mems will be the same with mems_allowed.

 *

 * Called with cpuset_mutex held

 * Called with cpuset_rwsem held

 */

static void update_nodemasks_hier(struct cpuset *cs, nodemask_t *new_mems)

{
@@ -1821,7 +1823,7 @@ static void update_nodemasks_hier(struct cpuset *cs, nodemask_t *new_mems) 
 * mempolicies and if the cpuset is marked 'memory_migrate',

 * migrate the tasks pages to the new memory.

 *

 * Call with cpuset_mutex held. May take callback_lock during call.

 * Call with cpuset_rwsem held. May take callback_lock during call.

 * Will take tasklist_lock, scan tasklist for tasks in cpuset cs,

 * lock each such tasks mm->mmap_lock, scan its vma's and rebind

 * their mempolicies to the cpusets new mems_allowed.
@@ -1911,7 +1913,7 @@ static int update_relax_domain_level(struct cpuset *cs, s64 val) 
 * @cs: the cpuset in which each task's spread flags needs to be changed

 *

 * Iterate through each task of @cs updating its spread flags.  As this

 * function is called with cpuset_mutex held, cpuset membership stays

 * function is called with cpuset_rwsem held, cpuset membership stays

 * stable.

 */

static void update_tasks_flags(struct cpuset *cs)
@@ -1931,7 +1933,7 @@ static void update_tasks_flags(struct cpuset *cs) 
 * cs:		the cpuset to update

 * turning_on: 	whether the flag is being set or cleared

 *

 * Call with cpuset_mutex held.

 * Call with cpuset_rwsem held.

 */



static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
@@ -1980,7 +1982,7 @@ static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs, 
 * cs: the cpuset to update

 * new_prs: new partition root state

 *

 * Call with cpuset_mutex held.

 * Call with cpuset_rwsem held.

 */

static int update_prstate(struct cpuset *cs, int new_prs)

{
@@ -2167,7 +2169,7 @@ static int fmeter_getrate(struct fmeter *fmp) 


static struct cpuset *cpuset_attach_old_cs;



/* Called by cgroups to determine if a cpuset is usable; cpuset_mutex held */

/* Called by cgroups to determine if a cpuset is usable; cpuset_rwsem held */

static int cpuset_can_attach(struct cgroup_taskset *tset)

{

	struct cgroup_subsys_state *css;
@@ -2219,7 +2221,7 @@ static void cpuset_cancel_attach(struct cgroup_taskset *tset) 
}



/*

 * Protected by cpuset_mutex.  cpus_attach is used only by cpuset_attach()

 * Protected by cpuset_rwsem.  cpus_attach is used only by cpuset_attach()

 * but we can't allocate it dynamically there.  Define it global and

 * allocate from cpuset_init().

 */
@@ -2227,7 +2229,7 @@ static cpumask_var_t cpus_attach; 


static void cpuset_attach(struct cgroup_taskset *tset)

{

	/* static buf protected by cpuset_mutex */

	/* static buf protected by cpuset_rwsem */

	static nodemask_t cpuset_attach_nodemask_to;

	struct task_struct *task;

	struct task_struct *leader;
@@ -2417,7 +2419,7 @@ static ssize_t cpuset_write_resmask(struct kernfs_open_file *of, 
	 * operation like this one can lead to a deadlock through kernfs

	 * active_ref protection.  Let's break the protection.  Losing the

	 * protection is okay as we check whether @cs is online after

	 * grabbing cpuset_mutex anyway.  This only happens on the legacy

	 * grabbing cpuset_rwsem anyway.  This only happens on the legacy

	 * hierarchies.

	 */

	css_get(&cs->css);
@@ -3672,7 +3674,7 @@ void __cpuset_memory_pressure_bump(void) 
 *  - Used for /proc/<pid>/cpuset.

 *  - No need to task_lock(tsk) on this tsk->cpuset reference, as it

 *    doesn't really matter if tsk->cpuset changes after we read it,

 *    and we take cpuset_mutex, keeping cpuset_attach() from changing it

 *    and we take cpuset_rwsem, keeping cpuset_attach() from changing it

 *    anyway.

 */

int proc_cpuset_show(struct seq_file *m, struct pid_namespace *ns,