From 9201bfcf2ffede3cef938fc734aebbd666c14d01 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 28 Sep 2021 14:24:28 +0200
Subject: [PATCH] sched: Move kprobes cleanup out of finish_task_switch()
References: bsc#1189998 (PREEMPT_RT prerequisite backports)
Patch-mainline: v5.16-rc1
Git-commit: 670721c7bd2a6e16e40db29b2707a27bdecd6928
Doing cleanups in the tail of schedule() is a latency punishment for the
incoming task. The point of invoking kprobes_task_flush() for a dead task
is that the instances are returned and cannot leak when __schedule() is
kprobed.
Move it into the delayed cleanup.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210928122411.537994026@linutronix.de
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
kernel/exit.c | 2 ++
kernel/kprobes.c | 8 ++++----
kernel/sched/core.c | 6 ------
3 files changed, 6 insertions(+), 10 deletions(-)
diff --git a/kernel/exit.c b/kernel/exit.c
index 9a89e7f36acb..9bbd40359bb6 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -64,6 +64,7 @@
#include <linux/rcuwait.h>
#include <linux/compat.h>
#include <linux/io_uring.h>
+#include <linux/kprobes.h>
#include <linux/uaccess.h>
#include <asm/unistd.h>
@@ -168,6 +169,7 @@ static void delayed_put_task_struct(struct rcu_head *rhp)
{
struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
+ kprobe_flush_task(tsk);
perf_event_delayed_put(tsk);
trace_sched_process_free(tsk);
put_task_struct(tsk);
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 790a573bbe00..9a38e7581a5c 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1250,10 +1250,10 @@ void kprobe_busy_end(void)
}
/*
- * This function is called from finish_task_switch when task tk becomes dead,
- * so that we can recycle any function-return probe instances associated
- * with this task. These left over instances represent probed functions
- * that have been called but will never return.
+ * This function is called from delayed_put_task_struct() when a task is
+ * dead and cleaned up to recycle any function-return probe instances
+ * associated with this task. These left over instances represent probed
+ * functions that have been called but will never return.
*/
void kprobe_flush_task(struct task_struct *tk)
{
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 6eb9def79dd5..1d0953ccddb7 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4661,12 +4661,6 @@ static struct rq *finish_task_switch(struct task_struct *prev)
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);