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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: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210928122411.537994026@linutronix.de
This commit is contained in:
Thomas Gleixner 2021-09-28 14:24:28 +02:00 committed by Peter Zijlstra
parent 539fbb5be0
commit 670721c7bd
3 changed files with 6 additions and 10 deletions
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2
kernel/exit.c
View File

@ -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);

8
kernel/kprobes.c
View File

@ -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)
{

6
kernel/sched/core.c
View File

@ -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);