From 670721c7bd2a6e16e40db29b2707a27bdecd6928 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 28 Sep 2021 14:24:28 +0200 Subject: [PATCH] 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 Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20210928122411.537994026@linutronix.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 91a43e57a32e..63851320ae73 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -64,6 +64,7 @@ #include #include #include +#include #include #include @@ -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 749284fc3c1f..e33b03c2bb9a 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -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);