From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Mon, 21 Nov 2016 19:31:08 +0100
Subject: [PATCH] kernel/sched: move stack + kprobe clean up to
 __put_task_struct()
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git
Git-commit: da77ceac3d20f27310a07a7c346a4ee6b40d6c28
Patch-mainline: Queued in subsystem maintainer repository
References: SLE Realtime Extension

There is no need to free the stack before the task struct (except for reasons
mentioned in commit 68f24b08ee89 ("sched/core: Free the stack early if
CONFIG_THREAD_INFO_IN_TASK")). This also comes handy on -RT because we can't
free memory in preempt disabled region.
vfree_atomic() delays the memory cleanup to a worker. Since we move everything
to the RCU callback, we can also free it immediately.

Cc: stable-rt@vger.kernel.org #for kprobe_flush_task()
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Daniel Wagner <dwagner@suse.de>
---
 kernel/fork.c       |   12 +++++++++++-
 kernel/sched/core.c |    9 ---------
 2 files changed, 11 insertions(+), 10 deletions(-)

--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -43,6 +43,7 @@
 #include <linux/hmm.h>
 #include <linux/fs.h>
 #include <linux/mm.h>
+#include <linux/kprobes.h>
 #include <linux/vmacache.h>
 #include <linux/nsproxy.h>
 #include <linux/capability.h>
@@ -289,7 +290,7 @@ static inline void free_thread_stack(str
 			return;
 		}
 
-		vfree_atomic(tsk->stack);
+		vfree(tsk->stack);
 		return;
 	}
 #endif
@@ -750,6 +751,15 @@ void __put_task_struct(struct task_struc
 	WARN_ON(refcount_read(&tsk->usage));
 	WARN_ON(tsk == current);
 
+	/*
+	 * Remove function-return probe instances associated with this
+	 * task and put them back on the free list.
+	 */
+	kprobe_flush_task(tsk);
+
+	/* Task is done with its stack. */
+	put_task_stack(tsk);
+
 	cgroup_free(tsk);
 	task_numa_free(tsk, true);
 	security_task_free(tsk);
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3253,15 +3253,6 @@ static struct rq *finish_task_switch(str
 		if (prev->sched_class->task_dead)
 			prev->sched_class->task_dead(prev);
 
-		/*
-		 * Remove function-return probe instances associated with this
-		 * 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_rcu_user(prev);
 	}