diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2019-06-14 17:46:14 -1000 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-06-14 17:46:14 -1000 |
commit | 0011572c883082a95e02d47f45fc4a42dc0e8634 (patch) | |
tree | 47ddda0da5f15354d4a93d3617de882cbd9064b3 /include | |
parent | 6aa7a22b97907851972d7f39aae79dc105eba78b (diff) | |
parent | d477f8c202d1f0d4791ab1263ca7657bbe5cf79e (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.h | 1 | ||||
-rw-r--r-- | include/linux/cgroup.h | 14 |
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(); } |