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authorLinus Torvalds <torvalds@linux-foundation.org>2019-06-14 17:46:14 -1000
committerLinus Torvalds <torvalds@linux-foundation.org>2019-06-14 17:46:14 -1000
commit0011572c883082a95e02d47f45fc4a42dc0e8634 (patch)
tree47ddda0da5f15354d4a93d3617de882cbd9064b3
parent6aa7a22b97907851972d7f39aae79dc105eba78b (diff)
parentd477f8c202d1f0d4791ab1263ca7657bbe5cf79e (diff)
downloadlinux-sh-0011572c883082a95e02d47f45fc4a42dc0e8634.tar.gz
Merge branch 'for-5.2-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup fixes from Tejun Heo: "This has an unusually high density of tricky fixes: - task_get_css() could deadlock when it races against a dying cgroup. - cgroup.procs didn't list thread group leaders with live threads. This could mislead readers to think that a cgroup is empty when it's not. Fixed by making PROCS iterator include dead tasks. I made a couple mistakes making this change and this pull request contains a couple follow-up patches. - When cpusets run out of online cpus, it updates cpusmasks of member tasks in bizarre ways. Joel improved the behavior significantly" * 'for-5.2-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: cpuset: restore sanity to cpuset_cpus_allowed_fallback() cgroup: Fix css_task_iter_advance_css_set() cset skip condition cgroup: css_task_iter_skip()'d iterators must be advanced before accessed cgroup: Include dying leaders with live threads in PROCS iterations cgroup: Implement css_task_iter_skip() cgroup: Call cgroup_release() before __exit_signal() docs cgroups: add another example size for hugetlb cgroup: Use css_tryget() instead of css_tryget_online() in task_get_css()
-rw-r--r--Documentation/cgroup-v1/hugetlb.txt22
-rw-r--r--include/linux/cgroup-defs.h1
-rw-r--r--include/linux/cgroup.h14
-rw-r--r--kernel/cgroup/cgroup.c106
-rw-r--r--kernel/cgroup/cpuset.c15
-rw-r--r--kernel/exit.c2
6 files changed, 117 insertions, 43 deletions
diff --git a/Documentation/cgroup-v1/hugetlb.txt b/Documentation/cgroup-v1/hugetlb.txt
index 106245c3aecc..1260e5369b9b 100644
--- a/Documentation/cgroup-v1/hugetlb.txt
+++ b/Documentation/cgroup-v1/hugetlb.txt
@@ -32,14 +32,18 @@ Brief summary of control files
hugetlb.<hugepagesize>.usage_in_bytes # show current usage for "hugepagesize" hugetlb
hugetlb.<hugepagesize>.failcnt # show the number of allocation failure due to HugeTLB limit
-For a system supporting two hugepage size (16M and 16G) the control
+For a system supporting three hugepage sizes (64k, 32M and 1G), the control
files include:
-hugetlb.16GB.limit_in_bytes
-hugetlb.16GB.max_usage_in_bytes
-hugetlb.16GB.usage_in_bytes
-hugetlb.16GB.failcnt
-hugetlb.16MB.limit_in_bytes
-hugetlb.16MB.max_usage_in_bytes
-hugetlb.16MB.usage_in_bytes
-hugetlb.16MB.failcnt
+hugetlb.1GB.limit_in_bytes
+hugetlb.1GB.max_usage_in_bytes
+hugetlb.1GB.usage_in_bytes
+hugetlb.1GB.failcnt
+hugetlb.64KB.limit_in_bytes
+hugetlb.64KB.max_usage_in_bytes
+hugetlb.64KB.usage_in_bytes
+hugetlb.64KB.failcnt
+hugetlb.32MB.limit_in_bytes
+hugetlb.32MB.max_usage_in_bytes
+hugetlb.32MB.usage_in_bytes
+hugetlb.32MB.failcnt
diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 11e215d7937e..b4e766e93f6e 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -221,6 +221,7 @@ struct css_set {
*/
struct list_head tasks;
struct list_head mg_tasks;
+ struct list_head dying_tasks;
/* all css_task_iters currently walking this cset */
struct list_head task_iters;
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index c0077adeea83..0297f930a56e 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -43,6 +43,9 @@
/* walk all threaded css_sets in the domain */
#define CSS_TASK_ITER_THREADED (1U << 1)
+/* internal flags */
+#define CSS_TASK_ITER_SKIPPED (1U << 16)
+
/* a css_task_iter should be treated as an opaque object */
struct css_task_iter {
struct cgroup_subsys *ss;
@@ -57,6 +60,7 @@ struct css_task_iter {
struct list_head *task_pos;
struct list_head *tasks_head;
struct list_head *mg_tasks_head;
+ struct list_head *dying_tasks_head;
struct css_set *cur_cset;
struct css_set *cur_dcset;
@@ -487,7 +491,7 @@ static inline struct cgroup_subsys_state *task_css(struct task_struct *task,
*
* Find the css for the (@task, @subsys_id) combination, increment a
* reference on and return it. This function is guaranteed to return a
- * valid css.
+ * valid css. The returned css may already have been offlined.
*/
static inline struct cgroup_subsys_state *
task_get_css(struct task_struct *task, int subsys_id)
@@ -497,7 +501,13 @@ task_get_css(struct task_struct *task, int subsys_id)
rcu_read_lock();
while (true) {
css = task_css(task, subsys_id);
- if (likely(css_tryget_online(css)))
+ /*
+ * Can't use css_tryget_online() here. A task which has
+ * PF_EXITING set may stay associated with an offline css.
+ * If such task calls this function, css_tryget_online()
+ * will keep failing.
+ */
+ if (likely(css_tryget(css)))
break;
cpu_relax();
}
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 426a0026225c..bf9dbffd46b1 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -215,7 +215,8 @@ static struct cftype cgroup_base_files[];
static int cgroup_apply_control(struct cgroup *cgrp);
static void cgroup_finalize_control(struct cgroup *cgrp, int ret);
-static void css_task_iter_advance(struct css_task_iter *it);
+static void css_task_iter_skip(struct css_task_iter *it,
+ struct task_struct *task);
static int cgroup_destroy_locked(struct cgroup *cgrp);
static struct cgroup_subsys_state *css_create(struct cgroup *cgrp,
struct cgroup_subsys *ss);
@@ -738,6 +739,7 @@ struct css_set init_css_set = {
.dom_cset = &init_css_set,
.tasks = LIST_HEAD_INIT(init_css_set.tasks),
.mg_tasks = LIST_HEAD_INIT(init_css_set.mg_tasks),
+ .dying_tasks = LIST_HEAD_INIT(init_css_set.dying_tasks),
.task_iters = LIST_HEAD_INIT(init_css_set.task_iters),
.threaded_csets = LIST_HEAD_INIT(init_css_set.threaded_csets),
.cgrp_links = LIST_HEAD_INIT(init_css_set.cgrp_links),
@@ -843,6 +845,21 @@ static void css_set_update_populated(struct css_set *cset, bool populated)
cgroup_update_populated(link->cgrp, populated);
}
+/*
+ * @task is leaving, advance task iterators which are pointing to it so
+ * that they can resume at the next position. Advancing an iterator might
+ * remove it from the list, use safe walk. See css_task_iter_skip() for
+ * details.
+ */
+static void css_set_skip_task_iters(struct css_set *cset,
+ struct task_struct *task)
+{
+ struct css_task_iter *it, *pos;
+
+ list_for_each_entry_safe(it, pos, &cset->task_iters, iters_node)
+ css_task_iter_skip(it, task);
+}
+
/**
* css_set_move_task - move a task from one css_set to another
* @task: task being moved
@@ -868,22 +885,9 @@ static void css_set_move_task(struct task_struct *task,
css_set_update_populated(to_cset, true);
if (from_cset) {
- struct css_task_iter *it, *pos;
-
WARN_ON_ONCE(list_empty(&task->cg_list));
- /*
- * @task is leaving, advance task iterators which are
- * pointing to it so that they can resume at the next
- * position. Advancing an iterator might remove it from
- * the list, use safe walk. See css_task_iter_advance*()
- * for details.
- */
- list_for_each_entry_safe(it, pos, &from_cset->task_iters,
- iters_node)
- if (it->task_pos == &task->cg_list)
- css_task_iter_advance(it);
-
+ css_set_skip_task_iters(from_cset, task);
list_del_init(&task->cg_list);
if (!css_set_populated(from_cset))
css_set_update_populated(from_cset, false);
@@ -1210,6 +1214,7 @@ static struct css_set *find_css_set(struct css_set *old_cset,
cset->dom_cset = cset;
INIT_LIST_HEAD(&cset->tasks);
INIT_LIST_HEAD(&cset->mg_tasks);
+ INIT_LIST_HEAD(&cset->dying_tasks);
INIT_LIST_HEAD(&cset->task_iters);
INIT_LIST_HEAD(&cset->threaded_csets);
INIT_HLIST_NODE(&cset->hlist);
@@ -4408,15 +4413,18 @@ static void css_task_iter_advance_css_set(struct css_task_iter *it)
it->task_pos = NULL;
return;
}
- } while (!css_set_populated(cset));
+ } while (!css_set_populated(cset) && list_empty(&cset->dying_tasks));
if (!list_empty(&cset->tasks))
it->task_pos = cset->tasks.next;
- else
+ else if (!list_empty(&cset->mg_tasks))
it->task_pos = cset->mg_tasks.next;
+ else
+ it->task_pos = cset->dying_tasks.next;
it->tasks_head = &cset->tasks;
it->mg_tasks_head = &cset->mg_tasks;
+ it->dying_tasks_head = &cset->dying_tasks;
/*
* We don't keep css_sets locked across iteration steps and thus
@@ -4442,9 +4450,20 @@ static void css_task_iter_advance_css_set(struct css_task_iter *it)
list_add(&it->iters_node, &cset->task_iters);
}
+static void css_task_iter_skip(struct css_task_iter *it,
+ struct task_struct *task)
+{
+ lockdep_assert_held(&css_set_lock);
+
+ if (it->task_pos == &task->cg_list) {
+ it->task_pos = it->task_pos->next;
+ it->flags |= CSS_TASK_ITER_SKIPPED;
+ }
+}
+
static void css_task_iter_advance(struct css_task_iter *it)
{
- struct list_head *next;
+ struct task_struct *task;
lockdep_assert_held(&css_set_lock);
repeat:
@@ -4454,25 +4473,40 @@ repeat:
* consumed first and then ->mg_tasks. After ->mg_tasks,
* we move onto the next cset.
*/
- next = it->task_pos->next;
-
- if (next == it->tasks_head)
- next = it->mg_tasks_head->next;
+ if (it->flags & CSS_TASK_ITER_SKIPPED)
+ it->flags &= ~CSS_TASK_ITER_SKIPPED;
+ else
+ it->task_pos = it->task_pos->next;
- if (next == it->mg_tasks_head)
+ if (it->task_pos == it->tasks_head)
+ it->task_pos = it->mg_tasks_head->next;
+ if (it->task_pos == it->mg_tasks_head)
+ it->task_pos = it->dying_tasks_head->next;
+ if (it->task_pos == it->dying_tasks_head)
css_task_iter_advance_css_set(it);
- else
- it->task_pos = next;
} else {
/* called from start, proceed to the first cset */
css_task_iter_advance_css_set(it);
}
- /* if PROCS, skip over tasks which aren't group leaders */
- if ((it->flags & CSS_TASK_ITER_PROCS) && it->task_pos &&
- !thread_group_leader(list_entry(it->task_pos, struct task_struct,
- cg_list)))
- goto repeat;
+ if (!it->task_pos)
+ return;
+
+ task = list_entry(it->task_pos, struct task_struct, cg_list);
+
+ if (it->flags & CSS_TASK_ITER_PROCS) {
+ /* if PROCS, skip over tasks which aren't group leaders */
+ if (!thread_group_leader(task))
+ goto repeat;
+
+ /* and dying leaders w/o live member threads */
+ if (!atomic_read(&task->signal->live))
+ goto repeat;
+ } else {
+ /* skip all dying ones */
+ if (task->flags & PF_EXITING)
+ goto repeat;
+ }
}
/**
@@ -4528,6 +4562,10 @@ struct task_struct *css_task_iter_next(struct css_task_iter *it)
spin_lock_irq(&css_set_lock);
+ /* @it may be half-advanced by skips, finish advancing */
+ if (it->flags & CSS_TASK_ITER_SKIPPED)
+ css_task_iter_advance(it);
+
if (it->task_pos) {
it->cur_task = list_entry(it->task_pos, struct task_struct,
cg_list);
@@ -6009,6 +6047,7 @@ void cgroup_exit(struct task_struct *tsk)
if (!list_empty(&tsk->cg_list)) {
spin_lock_irq(&css_set_lock);
css_set_move_task(tsk, cset, NULL, false);
+ list_add_tail(&tsk->cg_list, &cset->dying_tasks);
cset->nr_tasks--;
WARN_ON_ONCE(cgroup_task_frozen(tsk));
@@ -6034,6 +6073,13 @@ void cgroup_release(struct task_struct *task)
do_each_subsys_mask(ss, ssid, have_release_callback) {
ss->release(task);
} while_each_subsys_mask();
+
+ if (use_task_css_set_links) {
+ spin_lock_irq(&css_set_lock);
+ css_set_skip_task_iters(task_css_set(task), task);
+ list_del_init(&task->cg_list);
+ spin_unlock_irq(&css_set_lock);
+ }
}
void cgroup_free(struct task_struct *task)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 6a1942ed781c..515525ff1cfd 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -3254,10 +3254,23 @@ void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask)
spin_unlock_irqrestore(&callback_lock, flags);
}
+/**
+ * cpuset_cpus_allowed_fallback - final fallback before complete catastrophe.
+ * @tsk: pointer to task_struct with which the scheduler is struggling
+ *
+ * Description: In the case that the scheduler cannot find an allowed cpu in
+ * tsk->cpus_allowed, we fall back to task_cs(tsk)->cpus_allowed. In legacy
+ * mode however, this value is the same as task_cs(tsk)->effective_cpus,
+ * which will not contain a sane cpumask during cases such as cpu hotplugging.
+ * This is the absolute last resort for the scheduler and it is only used if
+ * _every_ other avenue has been traveled.
+ **/
+
void cpuset_cpus_allowed_fallback(struct task_struct *tsk)
{
rcu_read_lock();
- do_set_cpus_allowed(tsk, task_cs(tsk)->effective_cpus);
+ do_set_cpus_allowed(tsk, is_in_v2_mode() ?
+ task_cs(tsk)->cpus_allowed : cpu_possible_mask);
rcu_read_unlock();
/*
diff --git a/kernel/exit.c b/kernel/exit.c
index 1803efb2922f..a75b6a7f458a 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -195,6 +195,7 @@ repeat:
rcu_read_unlock();
proc_flush_task(p);
+ cgroup_release(p);
write_lock_irq(&tasklist_lock);
ptrace_release_task(p);
@@ -220,7 +221,6 @@ repeat:
}
write_unlock_irq(&tasklist_lock);
- cgroup_release(p);
release_thread(p);
call_rcu(&p->rcu, delayed_put_task_struct);