X-Git-Url: http://git.cascardo.info/?a=blobdiff_plain;f=kernel%2Fsched%2Fcore.c;h=23c6037e2d89b8cf93389d0a756b00f5bf668cbe;hb=68f24b08ee89;hp=2a906f20fba7c4ba63d89fe87ac3527607be453a;hpb=952b159f2919a8d514f13999f9f463bddcc1dae7;p=cascardo%2Flinux.git

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 2a906f20fba7..23c6037e2d89 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2016,6 +2016,28 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
 	success = 1; /* we're going to change ->state */
 	cpu = task_cpu(p);
 
+	/*
+	 * Ensure we load p->on_rq _after_ p->state, otherwise it would
+	 * be possible to, falsely, observe p->on_rq == 0 and get stuck
+	 * in smp_cond_load_acquire() below.
+	 *
+	 * sched_ttwu_pending()                 try_to_wake_up()
+	 *   [S] p->on_rq = 1;                  [L] P->state
+	 *       UNLOCK rq->lock  -----.
+	 *                              \
+	 *				 +---   RMB
+	 * schedule()                   /
+	 *       LOCK rq->lock    -----'
+	 *       UNLOCK rq->lock
+	 *
+	 * [task p]
+	 *   [S] p->state = UNINTERRUPTIBLE     [L] p->on_rq
+	 *
+	 * Pairs with the UNLOCK+LOCK on rq->lock from the
+	 * last wakeup of our task and the schedule that got our task
+	 * current.
+	 */
+	smp_rmb();
 	if (p->on_rq && ttwu_remote(p, wake_flags))
 		goto stat;
 
@@ -2750,6 +2772,10 @@ static struct rq *finish_task_switch(struct task_struct *prev)
 		 * task and put them back on the free list.
 		 */
 		kprobe_flush_task(prev);
+
+		/* Task is done with its stack. */
+		put_task_stack(prev);
+
 		put_task_struct(prev);
 	}
 
@@ -3381,7 +3407,6 @@ static void __sched notrace __schedule(bool preempt)
 
 	balance_callback(rq);
 }
-STACK_FRAME_NON_STANDARD(__schedule); /* switch_to() */
 
 static inline void sched_submit_work(struct task_struct *tsk)
 {