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authorLinus Torvalds <torvalds@linux-foundation.org>2017-04-11 23:38:16 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-04-11 23:38:16 -0700
commit06ea4c38bce80f3eb99b01d7c17419eb1a49fec2 (patch)
tree2af3797bce33f38ecfe39aa34ecec01e8ccd4b9c /include
parentaf94bdfa798b7da92cc82609acca61a287a004a4 (diff)
parentbfb0b80db5f9dca5ac0a5fd0edb765ee555e5a8e (diff)
Merge branch 'for-4.11-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup fixes from Tejun Heo: "This contains fixes for two long standing subtle bugs: - kthread_bind() on a new kthread binds it to specific CPUs and prevents userland from messing with the affinity or cgroup membership. Unfortunately, for cgroup membership, there's a window between kthread creation and kthread_bind*() invocation where the kthread can be moved into a non-root cgroup by userland. Depending on what controllers are in effect, this can assign the kthread unexpected attributes. For example, in the reported case, workqueue workers ended up in a non-root cpuset cgroups and had their CPU affinities overridden. This broke workqueue invariants and led to workqueue stalls. Fixed by closing the window between kthread creation and kthread_bind() as suggested by Oleg. - There was a bug in cgroup mount path which could allow two competing mount attempts to attach the same cgroup_root to two different superblocks. This was caused by mishandling return value from kernfs_pin_sb(). Fixed" * 'for-4.11-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: cgroup: avoid attaching a cgroup root to two different superblocks cgroup, kthread: close race window where new kthreads can be migrated to non-root cgroups
Diffstat (limited to 'include')
-rw-r--r--include/linux/cgroup.h21
-rw-r--r--include/linux/sched.h4
2 files changed, 25 insertions, 0 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index f6b43fbb141c..af9c86e958bd 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -570,6 +570,25 @@ static inline void pr_cont_cgroup_path(struct cgroup *cgrp)
pr_cont_kernfs_path(cgrp->kn);
}
+static inline void cgroup_init_kthreadd(void)
+{
+ /*
+ * kthreadd is inherited by all kthreads, keep it in the root so
+ * that the new kthreads are guaranteed to stay in the root until
+ * initialization is finished.
+ */
+ current->no_cgroup_migration = 1;
+}
+
+static inline void cgroup_kthread_ready(void)
+{
+ /*
+ * This kthread finished initialization. The creator should have
+ * set PF_NO_SETAFFINITY if this kthread should stay in the root.
+ */
+ current->no_cgroup_migration = 0;
+}
+
#else /* !CONFIG_CGROUPS */
struct cgroup_subsys_state;
@@ -590,6 +609,8 @@ static inline void cgroup_free(struct task_struct *p) {}
static inline int cgroup_init_early(void) { return 0; }
static inline int cgroup_init(void) { return 0; }
+static inline void cgroup_init_kthreadd(void) {}
+static inline void cgroup_kthread_ready(void) {}
static inline bool task_under_cgroup_hierarchy(struct task_struct *task,
struct cgroup *ancestor)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index d67eee84fd43..4cf9a59a4d08 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -604,6 +604,10 @@ struct task_struct {
#ifdef CONFIG_COMPAT_BRK
unsigned brk_randomized:1;
#endif
+#ifdef CONFIG_CGROUPS
+ /* disallow userland-initiated cgroup migration */
+ unsigned no_cgroup_migration:1;
+#endif
unsigned long atomic_flags; /* Flags requiring atomic access. */