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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 /include
parent6aa7a22b97907851972d7f39aae79dc105eba78b (diff)
parentd477f8c202d1f0d4791ab1263ca7657bbe5cf79e (diff)
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()
Diffstat (limited to 'include')
-rw-r--r--include/linux/cgroup-defs.h1
-rw-r--r--include/linux/cgroup.h14
2 files changed, 13 insertions, 2 deletions
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();
}