Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

cdc-wdm: s/kill_urbs/poison_urbs/ to fix build

Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 26 insertions, 10 deletions

diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index db27b69fa92a..cc25a3cff41f 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -972,7 +972,7 @@ void psi_cgroup_free(struct cgroup *cgroup)
  */
 void cgroup_move_task(struct task_struct *task, struct css_set *to)
 {
-	unsigned int task_flags = 0;
+	unsigned int task_flags;
 	struct rq_flags rf;
 	struct rq *rq;
 
@@ -987,15 +987,31 @@ void cgroup_move_task(struct task_struct *task, struct css_set *to)
 
 	rq = task_rq_lock(task, &rf);
 
-	if (task_on_rq_queued(task)) {
-		task_flags = TSK_RUNNING;
-		if (task_current(rq, task))
-			task_flags |= TSK_ONCPU;
-	} else if (task->in_iowait)
-		task_flags = TSK_IOWAIT;
-
-	if (task->in_memstall)
-		task_flags |= TSK_MEMSTALL;
+	/*
+	 * We may race with schedule() dropping the rq lock between
+	 * deactivating prev and switching to next. Because the psi
+	 * updates from the deactivation are deferred to the switch
+	 * callback to save cgroup tree updates, the task's scheduling
+	 * state here is not coherent with its psi state:
+	 *
+	 * schedule()                   cgroup_move_task()
+	 *   rq_lock()
+	 *   deactivate_task()
+	 *     p->on_rq = 0
+	 *     psi_dequeue() // defers TSK_RUNNING & TSK_IOWAIT updates
+	 *   pick_next_task()
+	 *     rq_unlock()
+	 *                                rq_lock()
+	 *                                psi_task_change() // old cgroup
+	 *                                task->cgroups = to
+	 *                                psi_task_change() // new cgroup
+	 *                                rq_unlock()
+	 *     rq_lock()
+	 *   psi_sched_switch() // does deferred updates in new cgroup
+	 *
+	 * Don't rely on the scheduling state. Use psi_flags instead.
+	 */
+	task_flags = task->psi_flags;
 
 	if (task_flags)
 		psi_task_change(task, task_flags, 0);