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Subject[PATCH 13/13] cpuset: replace cgroup_mutex locking with cpuset internal locking
Date
Supposedly for historical reasons, cpuset depends on cgroup core for
locking. It depends on cgroup_mutex in cgroup callbacks and grabs
cgroup_mutex from other places where it wants to be synchronized.
This is majorly messy and highly prone to introducing circular locking
dependency especially because cgroup_mutex is supposed to be one of
the outermost locks.

As previous patches already plugged possible races which may happen by
decoupling from cgroup_mutex, replacing cgroup_mutex with cpuset
specific cpuset_mutex is mostly straight-forward. Introduce
cpuset_mutex, replace all occurrences of cgroup_mutex with it, and add
cpuset_mutex locking to places which inherited cgroup_mutex from
cgroup core.

The only complication is from cpuset wanting to initiate task
migration when a cpuset loses all cpus or memory nodes. Task
migration may go through full cgroup and all subsystem locking and
should be initiated without holding any cpuset specific lock; however,
a previous patch already made hotplug handled asynchronously and
moving the task migration part outside other locks is easy.
cpuset_propagate_hotplug_workfn() now invokes
remove_tasks_in_empty_cpuset() without holding any lock.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
kernel/cpuset.c | 186 ++++++++++++++++++++++++++++++++------------------------
1 file changed, 106 insertions(+), 80 deletions(-)

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 79be3f0..2ee0e03 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -208,23 +208,20 @@ static struct cpuset top_cpuset = {
if (is_cpuset_online(((child_cs) = cgroup_cs((pos_cgrp)))))

/*
- * There are two global mutexes guarding cpuset structures. The first
- * is the main control groups cgroup_mutex, accessed via
- * cgroup_lock()/cgroup_unlock(). The second is the cpuset-specific
- * callback_mutex, below. They can nest. It is ok to first take
- * cgroup_mutex, then nest callback_mutex. We also require taking
- * task_lock() when dereferencing a task's cpuset pointer. See "The
- * task_lock() exception", at the end of this comment.
- *
- * A task must hold both mutexes to modify cpusets. If a task
- * holds cgroup_mutex, then it blocks others wanting that mutex,
- * ensuring that it is the only task able to also acquire callback_mutex
- * 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 cgroup_mutex. While it is
- * performing these checks, various callback routines can briefly
- * acquire callback_mutex to query cpusets. Once it is ready to make
- * the changes, it takes callback_mutex, blocking everyone else.
+ * There are two global mutexes guarding cpuset structures - cpuset_mutex
+ * and callback_mutex. The latter may nest inside the former. We also
+ * require taking task_lock() when dereferencing a task's cpuset pointer.
+ * See "The task_lock() exception", at the end of this comment.
+ *
+ * A task must hold both mutexes to modify cpusets. If a task holds
+ * cpuset_mutex, then it blocks others wanting that mutex, ensuring that it
+ * is the only task able to also acquire callback_mutex 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
+ * callback routines can briefly acquire callback_mutex to query cpusets.
+ * Once it is ready to make the changes, it takes callback_mutex, blocking
+ * everyone else.
*
* Calls to the kernel memory allocator can not be made while holding
* callback_mutex, as that would risk double tripping on callback_mutex
@@ -246,6 +243,7 @@ static struct cpuset top_cpuset = {
* guidelines for accessing subsystem state in kernel/cgroup.c
*/

+static DEFINE_MUTEX(cpuset_mutex);
static DEFINE_MUTEX(callback_mutex);

/*
@@ -351,7 +349,7 @@ static void guarantee_online_mems(const struct cpuset *cs, nodemask_t *pmask)
/*
* update task's spread flag if cpuset's page/slab spread flag is set
*
- * Called with callback_mutex/cgroup_mutex held
+ * Called with callback_mutex/cpuset_mutex held
*/
static void cpuset_update_task_spread_flag(struct cpuset *cs,
struct task_struct *tsk)
@@ -371,7 +369,7 @@ 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 cgroup_mutex.
+ * are only set if the other's are set. Call holding cpuset_mutex.
*/

static int is_cpuset_subset(const struct cpuset *p, const struct cpuset *q)
@@ -420,7 +418,7 @@ static void free_trial_cpuset(struct cpuset *trial)
* 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
- * cgroup_mutex held.
+ * cpuset_mutex held.
*
* 'cur' is the address of an actual, in-use cpuset. Operations
* such as list traversal that depend on the actual address of the
@@ -555,7 +553,7 @@ update_domain_attr_tree(struct sched_domain_attr *dattr, struct cpuset *c)
* domains when operating in the severe memory shortage situations
* that could cause allocation failures below.
*
- * Must be called with cgroup_lock held.
+ * Must be called with cpuset_mutex held.
*
* The three key local variables below are:
* q - a linked-list queue of cpuset pointers, used to implement a
@@ -766,7 +764,7 @@ done:
* 'cpus' is removed, then call this routine to rebuild the
* scheduler's dynamic sched domains.
*
- * Call with cgroup_mutex held. Takes get_online_cpus().
+ * Call with cpuset_mutex held. Takes get_online_cpus().
*/
static void rebuild_sched_domains_locked(void)
{
@@ -774,7 +772,7 @@ static void rebuild_sched_domains_locked(void)
cpumask_var_t *doms;
int ndoms;

- WARN_ON_ONCE(!cgroup_lock_is_held());
+ lockdep_assert_held(&cpuset_mutex);
get_online_cpus();

/* Generate domain masks and attrs */
@@ -800,9 +798,9 @@ static int generate_sched_domains(cpumask_var_t **domains,

void rebuild_sched_domains(void)
{
- cgroup_lock();
+ mutex_lock(&cpuset_mutex);
rebuild_sched_domains_locked();
- cgroup_unlock();
+ mutex_unlock(&cpuset_mutex);
}

/**
@@ -810,7 +808,7 @@ void rebuild_sched_domains(void)
* @tsk: task to test
* @scan: struct cgroup_scanner contained in its struct cpuset_hotplug_scanner
*
- * Call with cgroup_mutex held. May take callback_mutex during call.
+ * Call with cpuset_mutex held. May take callback_mutex during call.
* Called for each task in a cgroup by cgroup_scan_tasks().
* Return nonzero if this tasks's cpus_allowed mask should be changed (in other
* words, if its mask is not equal to its cpuset's mask).
@@ -831,7 +829,7 @@ static int cpuset_test_cpumask(struct task_struct *tsk,
* cpus_allowed mask needs to be changed.
*
* We don't need to re-check for the cgroup/cpuset membership, since we're
- * holding cgroup_lock() at this point.
+ * holding cpuset_mutex at this point.
*/
static void cpuset_change_cpumask(struct task_struct *tsk,
struct cgroup_scanner *scan)
@@ -844,7 +842,7 @@ static void cpuset_change_cpumask(struct task_struct *tsk,
* @cs: the cpuset in which each task's cpus_allowed mask needs to be changed
* @heap: if NULL, defer allocating heap memory to cgroup_scan_tasks()
*
- * Called with cgroup_mutex held
+ * Called with cpuset_mutex held
*
* The cgroup_scan_tasks() function will scan all the tasks in a cgroup,
* calling callback functions for each.
@@ -934,7 +932,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
* Temporarilly set tasks mems_allowed to target nodes of migration,
* so that the migration code can allocate pages on these nodes.
*
- * Call holding cgroup_mutex, so current's cpuset won't change
+ * Call holding cpuset_mutex, so current's cpuset won't change
* during this call, as manage_mutex holds off any cpuset_attach()
* calls. Therefore we don't need to take task_lock around the
* call to guarantee_online_mems(), as we know no one is changing
@@ -1009,7 +1007,7 @@ static void cpuset_change_task_nodemask(struct task_struct *tsk,
/*
* Update task's mems_allowed and rebind its mempolicy and vmas' mempolicy
* of it to cpuset's new mems_allowed, and migrate pages to new nodes if
- * memory_migrate flag is set. Called with cgroup_mutex held.
+ * memory_migrate flag is set. Called with cpuset_mutex held.
*/
static void cpuset_change_nodemask(struct task_struct *p,
struct cgroup_scanner *scan)
@@ -1018,7 +1016,7 @@ static void cpuset_change_nodemask(struct task_struct *p,
struct cpuset *cs;
int migrate;
const nodemask_t *oldmem = scan->data;
- static nodemask_t newmems; /* protected by cgroup_mutex */
+ static nodemask_t newmems; /* protected by cpuset_mutex */

cs = cgroup_cs(scan->cg);
guarantee_online_mems(cs, &newmems);
@@ -1045,7 +1043,7 @@ static void *cpuset_being_rebound;
* @oldmem: old mems_allowed of cpuset cs
* @heap: if NULL, defer allocating heap memory to cgroup_scan_tasks()
*
- * Called with cgroup_mutex held
+ * Called with cpuset_mutex held
* No return value. It's guaranteed that cgroup_scan_tasks() always returns 0
* if @heap != NULL.
*/
@@ -1067,7 +1065,7 @@ static void update_tasks_nodemask(struct cpuset *cs, const nodemask_t *oldmem,
* 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 cgroup_mutex, we know that no other rebind effort
+ * the global cpuset_mutex, 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.
@@ -1086,7 +1084,7 @@ static void update_tasks_nodemask(struct cpuset *cs, const nodemask_t *oldmem,
* mempolicies and if the cpuset is marked 'memory_migrate',
* migrate the tasks pages to the new memory.
*
- * Call with cgroup_mutex held. May take callback_mutex during call.
+ * Call with cpuset_mutex held. May take callback_mutex during call.
* Will take tasklist_lock, scan tasklist for tasks in cpuset cs,
* lock each such tasks mm->mmap_sem, scan its vma's and rebind
* their mempolicies to the cpusets new mems_allowed.
@@ -1184,7 +1182,7 @@ static int update_relax_domain_level(struct cpuset *cs, s64 val)
* Called by cgroup_scan_tasks() for each task in a cgroup.
*
* We don't need to re-check for the cgroup/cpuset membership, since we're
- * holding cgroup_lock() at this point.
+ * holding cpuset_mutex at this point.
*/
static void cpuset_change_flag(struct task_struct *tsk,
struct cgroup_scanner *scan)
@@ -1197,7 +1195,7 @@ static void cpuset_change_flag(struct task_struct *tsk,
* @cs: the cpuset in which each task's spread flags needs to be changed
* @heap: if NULL, defer allocating heap memory to cgroup_scan_tasks()
*
- * Called with cgroup_mutex held
+ * Called with cpuset_mutex held
*
* The cgroup_scan_tasks() function will scan all the tasks in a cgroup,
* calling callback functions for each.
@@ -1222,7 +1220,7 @@ static void update_tasks_flags(struct cpuset *cs, struct ptr_heap *heap)
* cs: the cpuset to update
* turning_on: whether the flag is being set or cleared
*
- * Call with cgroup_mutex held.
+ * Call with cpuset_mutex held.
*/

static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
@@ -1370,15 +1368,18 @@ static int fmeter_getrate(struct fmeter *fmp)
return val;
}

-/* Called by cgroups to determine if a cpuset is usable; cgroup_mutex held */
+/* Called by cgroups to determine if a cpuset is usable; cpuset_mutex held */
static int cpuset_can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
{
struct cpuset *cs = cgroup_cs(cgrp);
struct task_struct *task;
int ret;

+ mutex_lock(&cpuset_mutex);
+
+ ret = -ENOSPC;
if (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed))
- return -ENOSPC;
+ goto out_unlock;

cgroup_taskset_for_each(task, cgrp, tset) {
/*
@@ -1390,10 +1391,12 @@ static int cpuset_can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
* set_cpus_allowed_ptr() on all attached tasks before
* cpus_allowed may be changed.
*/
+ ret = -EINVAL;
if (task->flags & PF_THREAD_BOUND)
- return -EINVAL;
- if ((ret = security_task_setscheduler(task)))
- return ret;
+ goto out_unlock;
+ ret = security_task_setscheduler(task);
+ if (ret)
+ goto out_unlock;
}

/*
@@ -1401,19 +1404,23 @@ static int cpuset_can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
* changes which zero cpus/mems_allowed.
*/
cs->attach_in_progress++;
-
- return 0;
+ ret = 0;
+out_unlock:
+ mutex_unlock(&cpuset_mutex);
+ return ret;
}

static void cpuset_cancel_attach(struct cgroup *cgrp,
struct cgroup_taskset *tset)
{
+ mutex_lock(&cpuset_mutex);
cgroup_cs(cgrp)->attach_in_progress--;
+ mutex_unlock(&cpuset_mutex);
}

static void cpuset_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
{
- /* static bufs protected by cgroup_mutex */
+ /* static bufs protected by cpuset_mutex */
static cpumask_t cpus_attach;
static nodemask_t cpuset_attach_nodemask_from;
static nodemask_t cpuset_attach_nodemask_to;
@@ -1424,6 +1431,8 @@ static void cpuset_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
struct cpuset *cs = cgroup_cs(cgrp);
struct cpuset *oldcs = cgroup_cs(oldcgrp);

+ mutex_lock(&cpuset_mutex);
+
/* prepare for attach */
if (cs == &top_cpuset)
cpumask_copy(&cpus_attach, cpu_possible_mask);
@@ -1467,6 +1476,8 @@ static void cpuset_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
*/
if (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed))
schedule_cpuset_propagate_hotplug(cs);
+
+ mutex_unlock(&cpuset_mutex);
}

/* The various types of files and directories in a cpuset file system */
@@ -1488,12 +1499,13 @@ typedef enum {

static int cpuset_write_u64(struct cgroup *cgrp, struct cftype *cft, u64 val)
{
- int retval = 0;
struct cpuset *cs = cgroup_cs(cgrp);
cpuset_filetype_t type = cft->private;
+ int retval = -ENODEV;

- if (!cgroup_lock_live_group(cgrp))
- return -ENODEV;
+ mutex_lock(&cpuset_mutex);
+ if (!is_cpuset_online(cs))
+ goto out_unlock;

switch (type) {
case FILE_CPU_EXCLUSIVE:
@@ -1527,18 +1539,20 @@ static int cpuset_write_u64(struct cgroup *cgrp, struct cftype *cft, u64 val)
retval = -EINVAL;
break;
}
- cgroup_unlock();
+out_unlock:
+ mutex_unlock(&cpuset_mutex);
return retval;
}

static int cpuset_write_s64(struct cgroup *cgrp, struct cftype *cft, s64 val)
{
- int retval = 0;
struct cpuset *cs = cgroup_cs(cgrp);
cpuset_filetype_t type = cft->private;
+ int retval = -ENODEV;

- if (!cgroup_lock_live_group(cgrp))
- return -ENODEV;
+ mutex_lock(&cpuset_mutex);
+ if (!is_cpuset_online(cs))
+ goto out_unlock;

switch (type) {
case FILE_SCHED_RELAX_DOMAIN_LEVEL:
@@ -1548,7 +1562,8 @@ static int cpuset_write_s64(struct cgroup *cgrp, struct cftype *cft, s64 val)
retval = -EINVAL;
break;
}
- cgroup_unlock();
+out_unlock:
+ mutex_unlock(&cpuset_mutex);
return retval;
}

@@ -1558,9 +1573,9 @@ static int cpuset_write_s64(struct cgroup *cgrp, struct cftype *cft, s64 val)
static int cpuset_write_resmask(struct cgroup *cgrp, struct cftype *cft,
const char *buf)
{
- int retval = 0;
struct cpuset *cs = cgroup_cs(cgrp);
struct cpuset *trialcs;
+ int retval = -ENODEV;

/*
* CPU or memory hotunplug may leave @cs w/o any execution
@@ -1580,13 +1595,14 @@ static int cpuset_write_resmask(struct cgroup *cgrp, struct cftype *cft,
flush_work(&cpuset_hotplug_work);
flush_workqueue(cpuset_propagate_hotplug_wq);

- if (!cgroup_lock_live_group(cgrp))
- return -ENODEV;
+ mutex_lock(&cpuset_mutex);
+ if (!is_cpuset_online(cs))
+ goto out_unlock;

trialcs = alloc_trial_cpuset(cs);
if (!trialcs) {
retval = -ENOMEM;
- goto out;
+ goto out_unlock;
}

switch (cft->private) {
@@ -1602,8 +1618,8 @@ static int cpuset_write_resmask(struct cgroup *cgrp, struct cftype *cft,
}

free_trial_cpuset(trialcs);
-out:
- cgroup_unlock();
+out_unlock:
+ mutex_unlock(&cpuset_mutex);
return retval;
}

@@ -1861,6 +1877,8 @@ static int cpuset_css_online(struct cgroup *cgrp)
if (!parent)
return 0;

+ mutex_lock(&cpuset_mutex);
+
set_bit(CS_ONLINE, &cs->flags);
if (is_spread_page(parent))
set_bit(CS_SPREAD_PAGE, &cs->flags);
@@ -1870,7 +1888,7 @@ static int cpuset_css_online(struct cgroup *cgrp)
number_of_cpusets++;

if (!test_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags))
- return 0;
+ goto out_unlock;

/*
* Clone @parent's configuration if CGRP_CPUSET_CLONE_CHILDREN is
@@ -1889,7 +1907,7 @@ static int cpuset_css_online(struct cgroup *cgrp)
cpuset_for_each_child(tmp_cs, pos_cg, parent) {
if (is_mem_exclusive(tmp_cs) || is_cpu_exclusive(tmp_cs)) {
rcu_read_unlock();
- return 0;
+ goto out_unlock;
}
}
rcu_read_unlock();
@@ -1898,7 +1916,8 @@ static int cpuset_css_online(struct cgroup *cgrp)
cs->mems_allowed = parent->mems_allowed;
cpumask_copy(cs->cpus_allowed, parent->cpus_allowed);
mutex_unlock(&callback_mutex);
-
+out_unlock:
+ mutex_unlock(&cpuset_mutex);
return 0;
}

@@ -1906,8 +1925,7 @@ static void cpuset_css_offline(struct cgroup *cgrp)
{
struct cpuset *cs = cgroup_cs(cgrp);

- /* css_offline is called w/o cgroup_mutex, grab it */
- cgroup_lock();
+ mutex_lock(&cpuset_mutex);

if (is_sched_load_balance(cs))
update_flag(CS_SCHED_LOAD_BALANCE, cs, 0);
@@ -1915,7 +1933,7 @@ static void cpuset_css_offline(struct cgroup *cgrp)
number_of_cpusets--;
clear_bit(CS_ONLINE, &cs->flags);

- cgroup_unlock();
+ mutex_unlock(&cpuset_mutex);
}

/*
@@ -1987,7 +2005,9 @@ static void cpuset_do_move_task(struct task_struct *tsk,
{
struct cgroup *new_cgroup = scan->data;

+ cgroup_lock();
cgroup_attach_task(new_cgroup, tsk);
+ cgroup_unlock();
}

/**
@@ -1995,7 +2015,7 @@ static void cpuset_do_move_task(struct task_struct *tsk,
* @from: cpuset in which the tasks currently reside
* @to: cpuset to which the tasks will be moved
*
- * Called with cgroup_mutex held
+ * Called with cpuset_mutex held
* callback_mutex must not be held, as cpuset_attach() will take it.
*
* The cgroup_scan_tasks() function will scan all the tasks in a cgroup,
@@ -2022,9 +2042,6 @@ static void move_member_tasks_to_cpuset(struct cpuset *from, struct cpuset *to)
* removing that CPU or node from all cpusets. If this removes the
* last CPU or node from a cpuset, then move the tasks in the empty
* cpuset to its next-highest non-empty parent.
- *
- * Called with cgroup_mutex held
- * callback_mutex must not be held, as cpuset_attach() will take it.
*/
static void remove_tasks_in_empty_cpuset(struct cpuset *cs)
{
@@ -2080,8 +2097,9 @@ static void cpuset_propagate_hotplug_workfn(struct work_struct *work)
static cpumask_t off_cpus;
static nodemask_t off_mems, tmp_mems;
struct cpuset *cs = container_of(work, struct cpuset, hotplug_work);
+ bool is_empty;

- cgroup_lock();
+ mutex_lock(&cpuset_mutex);

cpumask_andnot(&off_cpus, cs->cpus_allowed, top_cpuset.cpus_allowed);
nodes_andnot(off_mems, cs->mems_allowed, top_cpuset.mems_allowed);
@@ -2103,10 +2121,18 @@ static void cpuset_propagate_hotplug_workfn(struct work_struct *work)
update_tasks_nodemask(cs, &tmp_mems, NULL);
}

- if (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed))
- remove_tasks_in_empty_cpuset(cs);
+ is_empty = cpumask_empty(cs->cpus_allowed) ||
+ nodes_empty(cs->mems_allowed);

- cgroup_unlock();
+ mutex_unlock(&cpuset_mutex);
+
+ /*
+ * If @cs became empty, move tasks to the nearest ancestor with
+ * execution resources. This is full cgroup operation which will
+ * also call back into cpuset. Should be done outside any lock.
+ */
+ if (is_empty)
+ remove_tasks_in_empty_cpuset(cs);

/* the following may free @cs, should be the last operation */
css_put(&cs->css);
@@ -2160,7 +2186,7 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
bool cpus_updated, mems_updated;
bool cpus_offlined, mems_offlined;

- cgroup_lock();
+ mutex_lock(&cpuset_mutex);

/* fetch the available cpus/mems and find out which changed how */
cpumask_copy(&new_cpus, cpu_active_mask);
@@ -2202,7 +2228,7 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
schedule_cpuset_propagate_hotplug(cs);
}

- cgroup_unlock();
+ mutex_unlock(&cpuset_mutex);

/* wait for propagations to finish */
flush_workqueue(cpuset_propagate_hotplug_wq);
@@ -2213,9 +2239,9 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
cpumask_var_t *doms;
int ndoms;

- cgroup_lock();
+ mutex_lock(&cpuset_mutex);
ndoms = generate_sched_domains(&doms, &attr);
- cgroup_unlock();
+ mutex_unlock(&cpuset_mutex);

partition_sched_domains(ndoms, doms, attr);
}
@@ -2630,7 +2656,7 @@ 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 cgroup_mutex, keeping cpuset_attach() from changing it
+ * and we take cpuset_mutex, keeping cpuset_attach() from changing it
* anyway.
*/
static int proc_cpuset_show(struct seq_file *m, void *unused_v)
@@ -2653,7 +2679,7 @@ static int proc_cpuset_show(struct seq_file *m, void *unused_v)
goto out_free;

retval = -EINVAL;
- cgroup_lock();
+ mutex_lock(&cpuset_mutex);
css = task_subsys_state(tsk, cpuset_subsys_id);
retval = cgroup_path(css->cgroup, buf, PAGE_SIZE);
if (retval < 0)
@@ -2661,7 +2687,7 @@ static int proc_cpuset_show(struct seq_file *m, void *unused_v)
seq_puts(m, buf);
seq_putc(m, '\n');
out_unlock:
- cgroup_unlock();
+ mutex_unlock(&cpuset_mutex);
put_task_struct(tsk);
out_free:
kfree(buf);
--
1.7.11.7


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