Merge branch 'for-3.9-cpuset' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cpuset changes from Tejun Heo:
- Synchornization has seen a lot of changes with focus on decoupling
cpuset synchronization from cgroup internal locking.
After this change, there only remain a couple of mostly trivial
dependencies on cgroup_lock outside cgroup core proper. cgroup_lock
is scheduled to be unexported in this devel cycle.
This will finally remove the fragile locking order around cgroup
(cgroup locking wants to / should be one of the outermost but yet has
been acquired from deep inside individual controllers).
- At this point, Li is most knowlegeable with cpuset and taking over
the maintainership of cpuset.
* 'for-3.9-cpuset' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cpuset: drop spurious retval assignment in proc_cpuset_show()
cpuset: fix RCU lockdep splat
cpuset: update MAINTAINERS
cpuset: remove cpuset->parent
cpuset: replace cpuset->stack_list with cpuset_for_each_descendant_pre()
cpuset: replace cgroup_mutex locking with cpuset internal locking
cpuset: schedule hotplug propagation from cpuset_attach() if the cpuset is empty
cpuset: pin down cpus and mems while a task is being attached
cpuset: make CPU / memory hotplug propagation asynchronous
cpuset: drop async_rebuild_sched_domains()
cpuset: don't nest cgroup_mutex inside get_online_cpus()
cpuset: reorganize CPU / memory hotplug handling
cpuset: cleanup cpuset[_can]_attach()
cpuset: introduce cpuset_for_each_child()
cpuset: introduce CS_ONLINE
cpuset: introduce ->css_on/offline()
cpuset: remove fast exit path from remove_tasks_in_empty_cpuset()
cpuset: remove unused cpuset_unlock()
diff --git a/MAINTAINERS b/MAINTAINERS
index 526fb85..b7013e4 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2140,10 +2140,10 @@
F: tools/power/cpupower
CPUSETS
-M: Paul Menage <paul@paulmenage.org>
+M: Li Zefan <lizefan@huawei.com>
W: http://www.bullopensource.org/cpuset/
W: http://oss.sgi.com/projects/cpusets/
-S: Supported
+S: Maintained
F: Documentation/cgroups/cpusets.txt
F: include/linux/cpuset.h
F: kernel/cpuset.c
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 5bb9bf1..4f9dfe4 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -61,14 +61,6 @@
#include <linux/cgroup.h>
/*
- * Workqueue for cpuset related tasks.
- *
- * Using kevent workqueue may cause deadlock when memory_migrate
- * is set. So we create a separate workqueue thread for cpuset.
- */
-static struct workqueue_struct *cpuset_wq;
-
-/*
* Tracks how many cpusets are currently defined in system.
* When there is only one cpuset (the root cpuset) we can
* short circuit some hooks.
@@ -95,18 +87,21 @@
cpumask_var_t cpus_allowed; /* CPUs allowed to tasks in cpuset */
nodemask_t mems_allowed; /* Memory Nodes allowed to tasks */
- struct cpuset *parent; /* my parent */
-
struct fmeter fmeter; /* memory_pressure filter */
+ /*
+ * Tasks are being attached to this cpuset. Used to prevent
+ * zeroing cpus/mems_allowed between ->can_attach() and ->attach().
+ */
+ int attach_in_progress;
+
/* partition number for rebuild_sched_domains() */
int pn;
/* for custom sched domain */
int relax_domain_level;
- /* used for walking a cpuset hierarchy */
- struct list_head stack_list;
+ struct work_struct hotplug_work;
};
/* Retrieve the cpuset for a cgroup */
@@ -123,6 +118,15 @@
struct cpuset, css);
}
+static inline struct cpuset *parent_cs(const struct cpuset *cs)
+{
+ struct cgroup *pcgrp = cs->css.cgroup->parent;
+
+ if (pcgrp)
+ return cgroup_cs(pcgrp);
+ return NULL;
+}
+
#ifdef CONFIG_NUMA
static inline bool task_has_mempolicy(struct task_struct *task)
{
@@ -138,6 +142,7 @@
/* bits in struct cpuset flags field */
typedef enum {
+ CS_ONLINE,
CS_CPU_EXCLUSIVE,
CS_MEM_EXCLUSIVE,
CS_MEM_HARDWALL,
@@ -147,13 +152,12 @@
CS_SPREAD_SLAB,
} cpuset_flagbits_t;
-/* the type of hotplug event */
-enum hotplug_event {
- CPUSET_CPU_OFFLINE,
- CPUSET_MEM_OFFLINE,
-};
-
/* convenient tests for these bits */
+static inline bool is_cpuset_online(const struct cpuset *cs)
+{
+ return test_bit(CS_ONLINE, &cs->flags);
+}
+
static inline int is_cpu_exclusive(const struct cpuset *cs)
{
return test_bit(CS_CPU_EXCLUSIVE, &cs->flags);
@@ -190,27 +194,52 @@
}
static struct cpuset top_cpuset = {
- .flags = ((1 << CS_CPU_EXCLUSIVE) | (1 << CS_MEM_EXCLUSIVE)),
+ .flags = ((1 << CS_ONLINE) | (1 << CS_CPU_EXCLUSIVE) |
+ (1 << CS_MEM_EXCLUSIVE)),
};
-/*
- * 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.
+/**
+ * cpuset_for_each_child - traverse online children of a cpuset
+ * @child_cs: loop cursor pointing to the current child
+ * @pos_cgrp: used for iteration
+ * @parent_cs: target cpuset to walk children of
*
- * 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.
+ * Walk @child_cs through the online children of @parent_cs. Must be used
+ * with RCU read locked.
+ */
+#define cpuset_for_each_child(child_cs, pos_cgrp, parent_cs) \
+ cgroup_for_each_child((pos_cgrp), (parent_cs)->css.cgroup) \
+ if (is_cpuset_online(((child_cs) = cgroup_cs((pos_cgrp)))))
+
+/**
+ * cpuset_for_each_descendant_pre - pre-order walk of a cpuset's descendants
+ * @des_cs: loop cursor pointing to the current descendant
+ * @pos_cgrp: used for iteration
+ * @root_cs: target cpuset to walk ancestor of
+ *
+ * Walk @des_cs through the online descendants of @root_cs. Must be used
+ * with RCU read locked. The caller may modify @pos_cgrp by calling
+ * cgroup_rightmost_descendant() to skip subtree.
+ */
+#define cpuset_for_each_descendant_pre(des_cs, pos_cgrp, root_cs) \
+ cgroup_for_each_descendant_pre((pos_cgrp), (root_cs)->css.cgroup) \
+ if (is_cpuset_online(((des_cs) = cgroup_cs((pos_cgrp)))))
+
+/*
+ * 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
@@ -232,6 +261,7 @@
* guidelines for accessing subsystem state in kernel/cgroup.c
*/
+static DEFINE_MUTEX(cpuset_mutex);
static DEFINE_MUTEX(callback_mutex);
/*
@@ -246,6 +276,17 @@
static DEFINE_SPINLOCK(cpuset_buffer_lock);
/*
+ * CPU / memory hotplug is handled asynchronously.
+ */
+static struct workqueue_struct *cpuset_propagate_hotplug_wq;
+
+static void cpuset_hotplug_workfn(struct work_struct *work);
+static void cpuset_propagate_hotplug_workfn(struct work_struct *work);
+static void schedule_cpuset_propagate_hotplug(struct cpuset *cs);
+
+static DECLARE_WORK(cpuset_hotplug_work, cpuset_hotplug_workfn);
+
+/*
* This is ugly, but preserves the userspace API for existing cpuset
* users. If someone tries to mount the "cpuset" filesystem, we
* silently switch it to mount "cgroup" instead
@@ -289,7 +330,7 @@
struct cpumask *pmask)
{
while (cs && !cpumask_intersects(cs->cpus_allowed, cpu_online_mask))
- cs = cs->parent;
+ cs = parent_cs(cs);
if (cs)
cpumask_and(pmask, cs->cpus_allowed, cpu_online_mask);
else
@@ -314,7 +355,7 @@
{
while (cs && !nodes_intersects(cs->mems_allowed,
node_states[N_MEMORY]))
- cs = cs->parent;
+ cs = parent_cs(cs);
if (cs)
nodes_and(*pmask, cs->mems_allowed,
node_states[N_MEMORY]);
@@ -326,7 +367,7 @@
/*
* 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)
@@ -346,7 +387,7 @@
*
* 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)
@@ -395,7 +436,7 @@
* 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
@@ -412,48 +453,58 @@
{
struct cgroup *cont;
struct cpuset *c, *par;
+ int ret;
+
+ rcu_read_lock();
/* Each of our child cpusets must be a subset of us */
- list_for_each_entry(cont, &cur->css.cgroup->children, sibling) {
- if (!is_cpuset_subset(cgroup_cs(cont), trial))
- return -EBUSY;
- }
+ ret = -EBUSY;
+ cpuset_for_each_child(c, cont, cur)
+ if (!is_cpuset_subset(c, trial))
+ goto out;
/* Remaining checks don't apply to root cpuset */
+ ret = 0;
if (cur == &top_cpuset)
- return 0;
+ goto out;
- par = cur->parent;
+ par = parent_cs(cur);
/* We must be a subset of our parent cpuset */
+ ret = -EACCES;
if (!is_cpuset_subset(trial, par))
- return -EACCES;
+ goto out;
/*
* If either I or some sibling (!= me) is exclusive, we can't
* overlap
*/
- list_for_each_entry(cont, &par->css.cgroup->children, sibling) {
- c = cgroup_cs(cont);
+ ret = -EINVAL;
+ cpuset_for_each_child(c, cont, par) {
if ((is_cpu_exclusive(trial) || is_cpu_exclusive(c)) &&
c != cur &&
cpumask_intersects(trial->cpus_allowed, c->cpus_allowed))
- return -EINVAL;
+ goto out;
if ((is_mem_exclusive(trial) || is_mem_exclusive(c)) &&
c != cur &&
nodes_intersects(trial->mems_allowed, c->mems_allowed))
- return -EINVAL;
+ goto out;
}
- /* Cpusets with tasks can't have empty cpus_allowed or mems_allowed */
- if (cgroup_task_count(cur->css.cgroup)) {
- if (cpumask_empty(trial->cpus_allowed) ||
- nodes_empty(trial->mems_allowed)) {
- return -ENOSPC;
- }
- }
+ /*
+ * Cpusets with tasks - existing or newly being attached - can't
+ * have empty cpus_allowed or mems_allowed.
+ */
+ ret = -ENOSPC;
+ if ((cgroup_task_count(cur->css.cgroup) || cur->attach_in_progress) &&
+ (cpumask_empty(trial->cpus_allowed) ||
+ nodes_empty(trial->mems_allowed)))
+ goto out;
- return 0;
+ ret = 0;
+out:
+ rcu_read_unlock();
+ return ret;
}
#ifdef CONFIG_SMP
@@ -474,31 +525,24 @@
return;
}
-static void
-update_domain_attr_tree(struct sched_domain_attr *dattr, struct cpuset *c)
+static void update_domain_attr_tree(struct sched_domain_attr *dattr,
+ struct cpuset *root_cs)
{
- LIST_HEAD(q);
+ struct cpuset *cp;
+ struct cgroup *pos_cgrp;
- list_add(&c->stack_list, &q);
- while (!list_empty(&q)) {
- struct cpuset *cp;
- struct cgroup *cont;
- struct cpuset *child;
-
- cp = list_first_entry(&q, struct cpuset, stack_list);
- list_del(q.next);
-
- if (cpumask_empty(cp->cpus_allowed))
+ rcu_read_lock();
+ cpuset_for_each_descendant_pre(cp, pos_cgrp, root_cs) {
+ /* skip the whole subtree if @cp doesn't have any CPU */
+ if (cpumask_empty(cp->cpus_allowed)) {
+ pos_cgrp = cgroup_rightmost_descendant(pos_cgrp);
continue;
+ }
if (is_sched_load_balance(cp))
update_domain_attr(dattr, cp);
-
- list_for_each_entry(cont, &cp->css.cgroup->children, sibling) {
- child = cgroup_cs(cont);
- list_add_tail(&child->stack_list, &q);
- }
}
+ rcu_read_unlock();
}
/*
@@ -520,7 +564,7 @@
* 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
@@ -558,7 +602,6 @@
static int generate_sched_domains(cpumask_var_t **domains,
struct sched_domain_attr **attributes)
{
- LIST_HEAD(q); /* queue of cpusets to be scanned */
struct cpuset *cp; /* scans q */
struct cpuset **csa; /* array of all cpuset ptrs */
int csn; /* how many cpuset ptrs in csa so far */
@@ -567,6 +610,7 @@
struct sched_domain_attr *dattr; /* attributes for custom domains */
int ndoms = 0; /* number of sched domains in result */
int nslot; /* next empty doms[] struct cpumask slot */
+ struct cgroup *pos_cgrp;
doms = NULL;
dattr = NULL;
@@ -594,33 +638,27 @@
goto done;
csn = 0;
- list_add(&top_cpuset.stack_list, &q);
- while (!list_empty(&q)) {
- struct cgroup *cont;
- struct cpuset *child; /* scans child cpusets of cp */
-
- cp = list_first_entry(&q, struct cpuset, stack_list);
- list_del(q.next);
-
- if (cpumask_empty(cp->cpus_allowed))
- continue;
-
+ rcu_read_lock();
+ cpuset_for_each_descendant_pre(cp, pos_cgrp, &top_cpuset) {
/*
- * All child cpusets contain a subset of the parent's cpus, so
- * just skip them, and then we call update_domain_attr_tree()
- * to calc relax_domain_level of the corresponding sched
- * domain.
+ * Continue traversing beyond @cp iff @cp has some CPUs and
+ * isn't load balancing. The former is obvious. The
+ * latter: All child cpusets contain a subset of the
+ * parent's cpus, so just skip them, and then we call
+ * update_domain_attr_tree() to calc relax_domain_level of
+ * the corresponding sched domain.
*/
- if (is_sched_load_balance(cp)) {
- csa[csn++] = cp;
+ if (!cpumask_empty(cp->cpus_allowed) &&
+ !is_sched_load_balance(cp))
continue;
- }
- list_for_each_entry(cont, &cp->css.cgroup->children, sibling) {
- child = cgroup_cs(cont);
- list_add_tail(&child->stack_list, &q);
- }
- }
+ if (is_sched_load_balance(cp))
+ csa[csn++] = cp;
+
+ /* skip @cp's subtree */
+ pos_cgrp = cgroup_rightmost_descendant(pos_cgrp);
+ }
+ rcu_read_unlock();
for (i = 0; i < csn; i++)
csa[i]->pn = i;
@@ -725,25 +763,25 @@
/*
* Rebuild scheduler domains.
*
- * Call with neither cgroup_mutex held nor within get_online_cpus().
- * Takes both cgroup_mutex and get_online_cpus().
+ * If the flag 'sched_load_balance' of any cpuset with non-empty
+ * 'cpus' changes, or if the 'cpus' allowed changes in any cpuset
+ * which has that flag enabled, or if any cpuset with a non-empty
+ * 'cpus' is removed, then call this routine to rebuild the
+ * scheduler's dynamic sched domains.
*
- * Cannot be directly called from cpuset code handling changes
- * to the cpuset pseudo-filesystem, because it cannot be called
- * from code that already holds cgroup_mutex.
+ * Call with cpuset_mutex held. Takes get_online_cpus().
*/
-static void do_rebuild_sched_domains(struct work_struct *unused)
+static void rebuild_sched_domains_locked(void)
{
struct sched_domain_attr *attr;
cpumask_var_t *doms;
int ndoms;
+ lockdep_assert_held(&cpuset_mutex);
get_online_cpus();
/* Generate domain masks and attrs */
- cgroup_lock();
ndoms = generate_sched_domains(&doms, &attr);
- cgroup_unlock();
/* Have scheduler rebuild the domains */
partition_sched_domains(ndoms, doms, attr);
@@ -751,7 +789,7 @@
put_online_cpus();
}
#else /* !CONFIG_SMP */
-static void do_rebuild_sched_domains(struct work_struct *unused)
+static void rebuild_sched_domains_locked(void)
{
}
@@ -763,44 +801,11 @@
}
#endif /* CONFIG_SMP */
-static DECLARE_WORK(rebuild_sched_domains_work, do_rebuild_sched_domains);
-
-/*
- * Rebuild scheduler domains, asynchronously via workqueue.
- *
- * If the flag 'sched_load_balance' of any cpuset with non-empty
- * 'cpus' changes, or if the 'cpus' allowed changes in any cpuset
- * which has that flag enabled, or if any cpuset with a non-empty
- * 'cpus' is removed, then call this routine to rebuild the
- * scheduler's dynamic sched domains.
- *
- * The rebuild_sched_domains() and partition_sched_domains()
- * routines must nest cgroup_lock() inside get_online_cpus(),
- * but such cpuset changes as these must nest that locking the
- * other way, holding cgroup_lock() for much of the code.
- *
- * So in order to avoid an ABBA deadlock, the cpuset code handling
- * these user changes delegates the actual sched domain rebuilding
- * to a separate workqueue thread, which ends up processing the
- * above do_rebuild_sched_domains() function.
- */
-static void async_rebuild_sched_domains(void)
-{
- queue_work(cpuset_wq, &rebuild_sched_domains_work);
-}
-
-/*
- * Accomplishes the same scheduler domain rebuild as the above
- * async_rebuild_sched_domains(), however it directly calls the
- * rebuild routine synchronously rather than calling it via an
- * asynchronous work thread.
- *
- * This can only be called from code that is not holding
- * cgroup_mutex (not nested in a cgroup_lock() call.)
- */
void rebuild_sched_domains(void)
{
- do_rebuild_sched_domains(NULL);
+ mutex_lock(&cpuset_mutex);
+ rebuild_sched_domains_locked();
+ mutex_unlock(&cpuset_mutex);
}
/**
@@ -808,7 +813,7 @@
* @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).
@@ -829,7 +834,7 @@
* 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)
@@ -842,7 +847,7 @@
* @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.
@@ -920,7 +925,7 @@
heap_free(&heap);
if (is_load_balanced)
- async_rebuild_sched_domains();
+ rebuild_sched_domains_locked();
return 0;
}
@@ -932,7 +937,7 @@
* 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
@@ -1007,7 +1012,7 @@
/*
* 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)
@@ -1016,7 +1021,7 @@
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);
@@ -1043,7 +1048,7 @@
* @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.
*/
@@ -1065,7 +1070,7 @@
* 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.
@@ -1084,7 +1089,7 @@
* 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.
@@ -1168,7 +1173,7 @@
cs->relax_domain_level = val;
if (!cpumask_empty(cs->cpus_allowed) &&
is_sched_load_balance(cs))
- async_rebuild_sched_domains();
+ rebuild_sched_domains_locked();
}
return 0;
@@ -1182,7 +1187,7 @@
* 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)
@@ -1195,7 +1200,7 @@
* @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.
@@ -1220,7 +1225,7 @@
* 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,
@@ -1260,7 +1265,7 @@
mutex_unlock(&callback_mutex);
if (!cpumask_empty(trialcs->cpus_allowed) && balance_flag_changed)
- async_rebuild_sched_domains();
+ rebuild_sched_domains_locked();
if (spread_flag_changed)
update_tasks_flags(cs, &heap);
@@ -1368,24 +1373,18 @@
return val;
}
-/*
- * Protected by cgroup_lock. The nodemasks must be stored globally because
- * dynamically allocating them is not allowed in can_attach, and they must
- * persist until attach.
- */
-static cpumask_var_t cpus_attach;
-static nodemask_t cpuset_attach_nodemask_from;
-static nodemask_t cpuset_attach_nodemask_to;
-
-/* 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) {
/*
@@ -1397,12 +1396,54 @@
* 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;
}
+ /*
+ * Mark attach is in progress. This makes validate_change() fail
+ * changes which zero cpus/mems_allowed.
+ */
+ cs->attach_in_progress++;
+ 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);
+}
+
+/*
+ * Protected by cpuset_mutex. cpus_attach is used only by cpuset_attach()
+ * but we can't allocate it dynamically there. Define it global and
+ * allocate from cpuset_init().
+ */
+static cpumask_var_t cpus_attach;
+
+static void cpuset_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
+{
+ /* static bufs protected by cpuset_mutex */
+ static nodemask_t cpuset_attach_nodemask_from;
+ static nodemask_t cpuset_attach_nodemask_to;
+ struct mm_struct *mm;
+ struct task_struct *task;
+ struct task_struct *leader = cgroup_taskset_first(tset);
+ struct cgroup *oldcgrp = cgroup_taskset_cur_cgroup(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);
@@ -1411,18 +1452,6 @@
guarantee_online_mems(cs, &cpuset_attach_nodemask_to);
- return 0;
-}
-
-static void cpuset_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
-{
- struct mm_struct *mm;
- struct task_struct *task;
- struct task_struct *leader = cgroup_taskset_first(tset);
- struct cgroup *oldcgrp = cgroup_taskset_cur_cgroup(tset);
- struct cpuset *cs = cgroup_cs(cgrp);
- struct cpuset *oldcs = cgroup_cs(oldcgrp);
-
cgroup_taskset_for_each(task, cgrp, tset) {
/*
* can_attach beforehand should guarantee that this doesn't
@@ -1448,6 +1477,18 @@
&cpuset_attach_nodemask_to);
mmput(mm);
}
+
+ cs->attach_in_progress--;
+
+ /*
+ * We may have raced with CPU/memory hotunplug. Trigger hotplug
+ * propagation if @cs doesn't have any CPU or memory. It will move
+ * the newly added tasks to the nearest parent which can execute.
+ */
+ 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 */
@@ -1469,12 +1510,13 @@
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:
@@ -1508,18 +1550,20 @@
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:
@@ -1529,7 +1573,8 @@
retval = -EINVAL;
break;
}
- cgroup_unlock();
+out_unlock:
+ mutex_unlock(&cpuset_mutex);
return retval;
}
@@ -1539,17 +1584,36 @@
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;
- if (!cgroup_lock_live_group(cgrp))
- return -ENODEV;
+ /*
+ * CPU or memory hotunplug may leave @cs w/o any execution
+ * resources, in which case the hotplug code asynchronously updates
+ * configuration and transfers all tasks to the nearest ancestor
+ * which can execute.
+ *
+ * As writes to "cpus" or "mems" may restore @cs's execution
+ * resources, wait for the previously scheduled operations before
+ * proceeding, so that we don't end up keep removing tasks added
+ * after execution capability is restored.
+ *
+ * Flushing cpuset_hotplug_work is enough to synchronize against
+ * hotplug hanlding; however, cpuset_attach() may schedule
+ * propagation work directly. Flush the workqueue too.
+ */
+ flush_work(&cpuset_hotplug_work);
+ flush_workqueue(cpuset_propagate_hotplug_wq);
+
+ 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) {
@@ -1565,8 +1629,8 @@
}
free_trial_cpuset(trialcs);
-out:
- cgroup_unlock();
+out_unlock:
+ mutex_unlock(&cpuset_mutex);
return retval;
}
@@ -1790,15 +1854,12 @@
static struct cgroup_subsys_state *cpuset_css_alloc(struct cgroup *cont)
{
- struct cgroup *parent_cg = cont->parent;
- struct cgroup *tmp_cg;
- struct cpuset *parent, *cs;
+ struct cpuset *cs;
- if (!parent_cg)
+ if (!cont->parent)
return &top_cpuset.css;
- parent = cgroup_cs(parent_cg);
- cs = kmalloc(sizeof(*cs), GFP_KERNEL);
+ cs = kzalloc(sizeof(*cs), GFP_KERNEL);
if (!cs)
return ERR_PTR(-ENOMEM);
if (!alloc_cpumask_var(&cs->cpus_allowed, GFP_KERNEL)) {
@@ -1806,22 +1867,38 @@
return ERR_PTR(-ENOMEM);
}
- cs->flags = 0;
- if (is_spread_page(parent))
- set_bit(CS_SPREAD_PAGE, &cs->flags);
- if (is_spread_slab(parent))
- set_bit(CS_SPREAD_SLAB, &cs->flags);
set_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
cpumask_clear(cs->cpus_allowed);
nodes_clear(cs->mems_allowed);
fmeter_init(&cs->fmeter);
+ INIT_WORK(&cs->hotplug_work, cpuset_propagate_hotplug_workfn);
cs->relax_domain_level = -1;
- cs->parent = parent;
+ return &cs->css;
+}
+
+static int cpuset_css_online(struct cgroup *cgrp)
+{
+ struct cpuset *cs = cgroup_cs(cgrp);
+ struct cpuset *parent = parent_cs(cs);
+ struct cpuset *tmp_cs;
+ struct cgroup *pos_cg;
+
+ 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);
+ if (is_spread_slab(parent))
+ set_bit(CS_SPREAD_SLAB, &cs->flags);
+
number_of_cpusets++;
- if (!test_bit(CGRP_CPUSET_CLONE_CHILDREN, &cont->flags))
- goto skip_clone;
+ if (!test_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags))
+ goto out_unlock;
/*
* Clone @parent's configuration if CGRP_CPUSET_CLONE_CHILDREN is
@@ -1836,35 +1913,49 @@
* changed to grant parent->cpus_allowed-sibling_cpus_exclusive
* (and likewise for mems) to the new cgroup.
*/
- list_for_each_entry(tmp_cg, &parent_cg->children, sibling) {
- struct cpuset *tmp_cs = cgroup_cs(tmp_cg);
-
- if (is_mem_exclusive(tmp_cs) || is_cpu_exclusive(tmp_cs))
- goto skip_clone;
+ rcu_read_lock();
+ cpuset_for_each_child(tmp_cs, pos_cg, parent) {
+ if (is_mem_exclusive(tmp_cs) || is_cpu_exclusive(tmp_cs)) {
+ rcu_read_unlock();
+ goto out_unlock;
+ }
}
+ rcu_read_unlock();
mutex_lock(&callback_mutex);
cs->mems_allowed = parent->mems_allowed;
cpumask_copy(cs->cpus_allowed, parent->cpus_allowed);
mutex_unlock(&callback_mutex);
-skip_clone:
- return &cs->css;
+out_unlock:
+ mutex_unlock(&cpuset_mutex);
+ return 0;
+}
+
+static void cpuset_css_offline(struct cgroup *cgrp)
+{
+ struct cpuset *cs = cgroup_cs(cgrp);
+
+ mutex_lock(&cpuset_mutex);
+
+ if (is_sched_load_balance(cs))
+ update_flag(CS_SCHED_LOAD_BALANCE, cs, 0);
+
+ number_of_cpusets--;
+ clear_bit(CS_ONLINE, &cs->flags);
+
+ mutex_unlock(&cpuset_mutex);
}
/*
* If the cpuset being removed has its flag 'sched_load_balance'
* enabled, then simulate turning sched_load_balance off, which
- * will call async_rebuild_sched_domains().
+ * will call rebuild_sched_domains_locked().
*/
static void cpuset_css_free(struct cgroup *cont)
{
struct cpuset *cs = cgroup_cs(cont);
- if (is_sched_load_balance(cs))
- update_flag(CS_SCHED_LOAD_BALANCE, cs, 0);
-
- number_of_cpusets--;
free_cpumask_var(cs->cpus_allowed);
kfree(cs);
}
@@ -1872,8 +1963,11 @@
struct cgroup_subsys cpuset_subsys = {
.name = "cpuset",
.css_alloc = cpuset_css_alloc,
+ .css_online = cpuset_css_online,
+ .css_offline = cpuset_css_offline,
.css_free = cpuset_css_free,
.can_attach = cpuset_can_attach,
+ .cancel_attach = cpuset_cancel_attach,
.attach = cpuset_attach,
.subsys_id = cpuset_subsys_id,
.base_cftypes = files,
@@ -1924,7 +2018,9 @@
{
struct cgroup *new_cgroup = scan->data;
+ cgroup_lock();
cgroup_attach_task(new_cgroup, tsk);
+ cgroup_unlock();
}
/**
@@ -1932,7 +2028,7 @@
* @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,
@@ -1959,169 +2055,200 @@
* 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)
{
struct cpuset *parent;
/*
- * The cgroup's css_sets list is in use if there are tasks
- * in the cpuset; the list is empty if there are none;
- * the cs->css.refcnt seems always 0.
- */
- if (list_empty(&cs->css.cgroup->css_sets))
- return;
-
- /*
* Find its next-highest non-empty parent, (top cpuset
* has online cpus, so can't be empty).
*/
- parent = cs->parent;
+ parent = parent_cs(cs);
while (cpumask_empty(parent->cpus_allowed) ||
nodes_empty(parent->mems_allowed))
- parent = parent->parent;
+ parent = parent_cs(parent);
move_member_tasks_to_cpuset(cs, parent);
}
-/*
- * Helper function to traverse cpusets.
- * It can be used to walk the cpuset tree from top to bottom, completing
- * one layer before dropping down to the next (thus always processing a
- * node before any of its children).
+/**
+ * cpuset_propagate_hotplug_workfn - propagate CPU/memory hotplug to a cpuset
+ * @cs: cpuset in interest
+ *
+ * Compare @cs's cpu and mem masks against top_cpuset and if some have gone
+ * offline, update @cs accordingly. If @cs ends up with no CPU or memory,
+ * all its tasks are moved to the nearest ancestor with both resources.
*/
-static struct cpuset *cpuset_next(struct list_head *queue)
+static void cpuset_propagate_hotplug_workfn(struct work_struct *work)
{
- struct cpuset *cp;
- struct cpuset *child; /* scans child cpusets of cp */
- struct cgroup *cont;
+ 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;
- if (list_empty(queue))
- return NULL;
+ mutex_lock(&cpuset_mutex);
- cp = list_first_entry(queue, struct cpuset, stack_list);
- list_del(queue->next);
- list_for_each_entry(cont, &cp->css.cgroup->children, sibling) {
- child = cgroup_cs(cont);
- list_add_tail(&child->stack_list, queue);
+ cpumask_andnot(&off_cpus, cs->cpus_allowed, top_cpuset.cpus_allowed);
+ nodes_andnot(off_mems, cs->mems_allowed, top_cpuset.mems_allowed);
+
+ /* remove offline cpus from @cs */
+ if (!cpumask_empty(&off_cpus)) {
+ mutex_lock(&callback_mutex);
+ cpumask_andnot(cs->cpus_allowed, cs->cpus_allowed, &off_cpus);
+ mutex_unlock(&callback_mutex);
+ update_tasks_cpumask(cs, NULL);
}
- return cp;
+ /* remove offline mems from @cs */
+ if (!nodes_empty(off_mems)) {
+ tmp_mems = cs->mems_allowed;
+ mutex_lock(&callback_mutex);
+ nodes_andnot(cs->mems_allowed, cs->mems_allowed, off_mems);
+ mutex_unlock(&callback_mutex);
+ update_tasks_nodemask(cs, &tmp_mems, NULL);
+ }
+
+ is_empty = cpumask_empty(cs->cpus_allowed) ||
+ nodes_empty(cs->mems_allowed);
+
+ 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);
}
-
-/*
- * Walk the specified cpuset subtree upon a hotplug operation (CPU/Memory
- * online/offline) and update the cpusets accordingly.
- * For regular CPU/Mem hotplug, look for empty cpusets; the tasks of such
- * cpuset must be moved to a parent cpuset.
+/**
+ * schedule_cpuset_propagate_hotplug - schedule hotplug propagation to a cpuset
+ * @cs: cpuset of interest
*
- * Called with cgroup_mutex held. We take callback_mutex to modify
- * cpus_allowed and mems_allowed.
- *
- * This walk processes the tree from top to bottom, completing one layer
- * before dropping down to the next. It always processes a node before
- * any of its children.
- *
- * In the case of memory hot-unplug, it will remove nodes from N_MEMORY
- * if all present pages from a node are offlined.
+ * Schedule cpuset_propagate_hotplug_workfn() which will update CPU and
+ * memory masks according to top_cpuset.
*/
-static void
-scan_cpusets_upon_hotplug(struct cpuset *root, enum hotplug_event event)
+static void schedule_cpuset_propagate_hotplug(struct cpuset *cs)
{
- LIST_HEAD(queue);
- struct cpuset *cp; /* scans cpusets being updated */
- static nodemask_t oldmems; /* protected by cgroup_mutex */
+ /*
+ * Pin @cs. The refcnt will be released when the work item
+ * finishes executing.
+ */
+ if (!css_tryget(&cs->css))
+ return;
- list_add_tail((struct list_head *)&root->stack_list, &queue);
+ /*
+ * Queue @cs->hotplug_work. If already pending, lose the css ref.
+ * cpuset_propagate_hotplug_wq is ordered and propagation will
+ * happen in the order this function is called.
+ */
+ if (!queue_work(cpuset_propagate_hotplug_wq, &cs->hotplug_work))
+ css_put(&cs->css);
+}
- switch (event) {
- case CPUSET_CPU_OFFLINE:
- while ((cp = cpuset_next(&queue)) != NULL) {
+/**
+ * cpuset_hotplug_workfn - handle CPU/memory hotunplug for a cpuset
+ *
+ * This function is called after either CPU or memory configuration has
+ * changed and updates cpuset accordingly. The top_cpuset is always
+ * synchronized to cpu_active_mask and N_MEMORY, which is necessary in
+ * order to make cpusets transparent (of no affect) on systems that are
+ * actively using CPU hotplug but making no active use of cpusets.
+ *
+ * Non-root cpusets are only affected by offlining. If any CPUs or memory
+ * nodes have been taken down, cpuset_propagate_hotplug() is invoked on all
+ * descendants.
+ *
+ * Note that CPU offlining during suspend is ignored. We don't modify
+ * cpusets across suspend/resume cycles at all.
+ */
+static void cpuset_hotplug_workfn(struct work_struct *work)
+{
+ static cpumask_t new_cpus, tmp_cpus;
+ static nodemask_t new_mems, tmp_mems;
+ bool cpus_updated, mems_updated;
+ bool cpus_offlined, mems_offlined;
- /* Continue past cpusets with all cpus online */
- if (cpumask_subset(cp->cpus_allowed, cpu_active_mask))
- continue;
+ mutex_lock(&cpuset_mutex);
- /* Remove offline cpus from this cpuset. */
- mutex_lock(&callback_mutex);
- cpumask_and(cp->cpus_allowed, cp->cpus_allowed,
- cpu_active_mask);
- mutex_unlock(&callback_mutex);
+ /* fetch the available cpus/mems and find out which changed how */
+ cpumask_copy(&new_cpus, cpu_active_mask);
+ new_mems = node_states[N_MEMORY];
- /* Move tasks from the empty cpuset to a parent */
- if (cpumask_empty(cp->cpus_allowed))
- remove_tasks_in_empty_cpuset(cp);
- else
- update_tasks_cpumask(cp, NULL);
- }
- break;
+ cpus_updated = !cpumask_equal(top_cpuset.cpus_allowed, &new_cpus);
+ cpus_offlined = cpumask_andnot(&tmp_cpus, top_cpuset.cpus_allowed,
+ &new_cpus);
- case CPUSET_MEM_OFFLINE:
- while ((cp = cpuset_next(&queue)) != NULL) {
+ mems_updated = !nodes_equal(top_cpuset.mems_allowed, new_mems);
+ nodes_andnot(tmp_mems, top_cpuset.mems_allowed, new_mems);
+ mems_offlined = !nodes_empty(tmp_mems);
- /* Continue past cpusets with all mems online */
- if (nodes_subset(cp->mems_allowed,
- node_states[N_MEMORY]))
- continue;
+ /* synchronize cpus_allowed to cpu_active_mask */
+ if (cpus_updated) {
+ mutex_lock(&callback_mutex);
+ cpumask_copy(top_cpuset.cpus_allowed, &new_cpus);
+ mutex_unlock(&callback_mutex);
+ /* we don't mess with cpumasks of tasks in top_cpuset */
+ }
- oldmems = cp->mems_allowed;
+ /* synchronize mems_allowed to N_MEMORY */
+ if (mems_updated) {
+ tmp_mems = top_cpuset.mems_allowed;
+ mutex_lock(&callback_mutex);
+ top_cpuset.mems_allowed = new_mems;
+ mutex_unlock(&callback_mutex);
+ update_tasks_nodemask(&top_cpuset, &tmp_mems, NULL);
+ }
- /* Remove offline mems from this cpuset. */
- mutex_lock(&callback_mutex);
- nodes_and(cp->mems_allowed, cp->mems_allowed,
- node_states[N_MEMORY]);
- mutex_unlock(&callback_mutex);
+ /* if cpus or mems went down, we need to propagate to descendants */
+ if (cpus_offlined || mems_offlined) {
+ struct cpuset *cs;
+ struct cgroup *pos_cgrp;
- /* Move tasks from the empty cpuset to a parent */
- if (nodes_empty(cp->mems_allowed))
- remove_tasks_in_empty_cpuset(cp);
- else
- update_tasks_nodemask(cp, &oldmems, NULL);
- }
+ rcu_read_lock();
+ cpuset_for_each_descendant_pre(cs, pos_cgrp, &top_cpuset)
+ schedule_cpuset_propagate_hotplug(cs);
+ rcu_read_unlock();
+ }
+
+ mutex_unlock(&cpuset_mutex);
+
+ /* wait for propagations to finish */
+ flush_workqueue(cpuset_propagate_hotplug_wq);
+
+ /* rebuild sched domains if cpus_allowed has changed */
+ if (cpus_updated) {
+ struct sched_domain_attr *attr;
+ cpumask_var_t *doms;
+ int ndoms;
+
+ mutex_lock(&cpuset_mutex);
+ ndoms = generate_sched_domains(&doms, &attr);
+ mutex_unlock(&cpuset_mutex);
+
+ partition_sched_domains(ndoms, doms, attr);
}
}
-/*
- * The top_cpuset tracks what CPUs and Memory Nodes are online,
- * period. This is necessary in order to make cpusets transparent
- * (of no affect) on systems that are actively using CPU hotplug
- * but making no active use of cpusets.
- *
- * The only exception to this is suspend/resume, where we don't
- * modify cpusets at all.
- *
- * This routine ensures that top_cpuset.cpus_allowed tracks
- * cpu_active_mask on each CPU hotplug (cpuhp) event.
- *
- * Called within get_online_cpus(). Needs to call cgroup_lock()
- * before calling generate_sched_domains().
- *
- * @cpu_online: Indicates whether this is a CPU online event (true) or
- * a CPU offline event (false).
- */
void cpuset_update_active_cpus(bool cpu_online)
{
- struct sched_domain_attr *attr;
- cpumask_var_t *doms;
- int ndoms;
-
- cgroup_lock();
- mutex_lock(&callback_mutex);
- cpumask_copy(top_cpuset.cpus_allowed, cpu_active_mask);
- mutex_unlock(&callback_mutex);
-
- if (!cpu_online)
- scan_cpusets_upon_hotplug(&top_cpuset, CPUSET_CPU_OFFLINE);
-
- ndoms = generate_sched_domains(&doms, &attr);
- cgroup_unlock();
-
- /* Have scheduler rebuild the domains */
- partition_sched_domains(ndoms, doms, attr);
+ /*
+ * We're inside cpu hotplug critical region which usually nests
+ * inside cgroup synchronization. Bounce actual hotplug processing
+ * to a work item to avoid reverse locking order.
+ *
+ * We still need to do partition_sched_domains() synchronously;
+ * otherwise, the scheduler will get confused and put tasks to the
+ * dead CPU. Fall back to the default single domain.
+ * cpuset_hotplug_workfn() will rebuild it as necessary.
+ */
+ partition_sched_domains(1, NULL, NULL);
+ schedule_work(&cpuset_hotplug_work);
}
#ifdef CONFIG_MEMORY_HOTPLUG
@@ -2133,29 +2260,7 @@
static int cpuset_track_online_nodes(struct notifier_block *self,
unsigned long action, void *arg)
{
- static nodemask_t oldmems; /* protected by cgroup_mutex */
-
- cgroup_lock();
- switch (action) {
- case MEM_ONLINE:
- oldmems = top_cpuset.mems_allowed;
- mutex_lock(&callback_mutex);
- top_cpuset.mems_allowed = node_states[N_MEMORY];
- mutex_unlock(&callback_mutex);
- update_tasks_nodemask(&top_cpuset, &oldmems, NULL);
- break;
- case MEM_OFFLINE:
- /*
- * needn't update top_cpuset.mems_allowed explicitly because
- * scan_cpusets_upon_hotplug() will update it.
- */
- scan_cpusets_upon_hotplug(&top_cpuset, CPUSET_MEM_OFFLINE);
- break;
- default:
- break;
- }
- cgroup_unlock();
-
+ schedule_work(&cpuset_hotplug_work);
return NOTIFY_OK;
}
#endif
@@ -2173,8 +2278,9 @@
hotplug_memory_notifier(cpuset_track_online_nodes, 10);
- cpuset_wq = create_singlethread_workqueue("cpuset");
- BUG_ON(!cpuset_wq);
+ cpuset_propagate_hotplug_wq =
+ alloc_ordered_workqueue("cpuset_hotplug", 0);
+ BUG_ON(!cpuset_propagate_hotplug_wq);
}
/**
@@ -2273,8 +2379,8 @@
*/
static const struct cpuset *nearest_hardwall_ancestor(const struct cpuset *cs)
{
- while (!(is_mem_exclusive(cs) || is_mem_hardwall(cs)) && cs->parent)
- cs = cs->parent;
+ while (!(is_mem_exclusive(cs) || is_mem_hardwall(cs)) && parent_cs(cs))
+ cs = parent_cs(cs);
return cs;
}
@@ -2412,17 +2518,6 @@
}
/**
- * cpuset_unlock - release lock on cpuset changes
- *
- * Undo the lock taken in a previous cpuset_lock() call.
- */
-
-void cpuset_unlock(void)
-{
- mutex_unlock(&callback_mutex);
-}
-
-/**
* cpuset_mem_spread_node() - On which node to begin search for a file page
* cpuset_slab_spread_node() - On which node to begin search for a slab page
*
@@ -2568,7 +2663,7 @@
* - 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)
@@ -2590,16 +2685,15 @@
if (!tsk)
goto out_free;
- retval = -EINVAL;
- cgroup_lock();
+ rcu_read_lock();
css = task_subsys_state(tsk, cpuset_subsys_id);
retval = cgroup_path(css->cgroup, buf, PAGE_SIZE);
+ rcu_read_unlock();
if (retval < 0)
- goto out_unlock;
+ goto out_put_task;
seq_puts(m, buf);
seq_putc(m, '\n');
-out_unlock:
- cgroup_unlock();
+out_put_task:
put_task_struct(tsk);
out_free:
kfree(buf);
