linux-kernel - Re: [PATCH tip/core/rcu 20/41] kprobes: eplace synchronize_sched() with synchronize

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Message-Id: <20181112120048.12b3fb7549f4b292fea1eefd@kernel.org>
Date:   Mon, 12 Nov 2018 12:00:48 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     "Paul E. McKenney" <paulmck@...ux.ibm.com>
Cc:     linux-kernel@...r.kernel.org, mingo@...nel.org,
        jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        fweisbec@...il.com, oleg@...hat.com, joel@...lfernandes.org,
        "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: Re: [PATCH tip/core/rcu 20/41] kprobes: eplace synchronize_sched()
 with synchronize_rcu()

On Sun, 11 Nov 2018 11:43:49 -0800
"Paul E. McKenney" <paulmck@...ux.ibm.com> wrote:

> Now that synchronize_rcu() waits for preempt-disable regions of code
> as well as RCU read-side critical sections, synchronize_sched() can be
> replaced by synchronize_rcu().  This commit therefore makes this change.

Would you mean synchronize_rcu() can ensure that any interrupt handler
(which should run under preempt-disable state) run out (even on non-preemptive
kernel)?
If so, I agree with these changes.

Thank you,

> 
> Signed-off-by: Paul E. McKenney <paulmck@...ux.ibm.com>
> Cc: "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>
> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Masami Hiramatsu <mhiramat@...nel.org>
> ---
>  kernel/kprobes.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 90e98e233647..08e31d863191 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -229,7 +229,7 @@ static int collect_garbage_slots(struct kprobe_insn_cache *c)
>  	struct kprobe_insn_page *kip, *next;
>  
>  	/* Ensure no-one is interrupted on the garbages */
> -	synchronize_sched();
> +	synchronize_rcu();
>  
>  	list_for_each_entry_safe(kip, next, &c->pages, list) {
>  		int i;
> @@ -1382,7 +1382,7 @@ static int register_aggr_kprobe(struct kprobe *orig_p, struct kprobe *p)
>  			if (ret) {
>  				ap->flags |= KPROBE_FLAG_DISABLED;
>  				list_del_rcu(&p->list);
> -				synchronize_sched();
> +				synchronize_rcu();
>  			}
>  		}
>  	}
> @@ -1597,7 +1597,7 @@ int register_kprobe(struct kprobe *p)
>  		ret = arm_kprobe(p);
>  		if (ret) {
>  			hlist_del_rcu(&p->hlist);
> -			synchronize_sched();
> +			synchronize_rcu();
>  			goto out;
>  		}
>  	}
> @@ -1776,7 +1776,7 @@ void unregister_kprobes(struct kprobe **kps, int num)
>  			kps[i]->addr = NULL;
>  	mutex_unlock(&kprobe_mutex);
>  
> -	synchronize_sched();
> +	synchronize_rcu();
>  	for (i = 0; i < num; i++)
>  		if (kps[i]->addr)
>  			__unregister_kprobe_bottom(kps[i]);
> @@ -1966,7 +1966,7 @@ void unregister_kretprobes(struct kretprobe **rps, int num)
>  			rps[i]->kp.addr = NULL;
>  	mutex_unlock(&kprobe_mutex);
>  
> -	synchronize_sched();
> +	synchronize_rcu();
>  	for (i = 0; i < num; i++) {
>  		if (rps[i]->kp.addr) {
>  			__unregister_kprobe_bottom(&rps[i]->kp);
> -- 
> 2.17.1
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>