Commit 670721c7 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Peter Zijlstra
Browse files

sched: Move kprobes cleanup out of finish_task_switch() 



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: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210928122411.537994026@linutronix.de
parent 539fbb5b

kernel/exit.c

+2 −0
Original line number Diff line number Diff line
@@ -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);

kernel/kprobes.c

+4 −4
Original line number Diff line number Diff line
@@ -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)

{

kernel/sched/core.c

+0 −6
Original line number Diff line number Diff line
@@ -4846,12 +4846,6 @@ 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);