Re: [PATCH tip/core/rcu 20/41] kprobes: eplace synchronize_sched() with synchronize_rcu()

Masami Hiramatsu
2018-11-12T03:00:55Z

On Sun, 11 Nov 2018 11:43:49 -0800
"Paul E. McKenney" <paulmck@linux.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@linux.ibm.com>
> Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Masami Hiramatsu <mhiramat@kernel.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@kernel.org>