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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 12 Nov 2018 03:24:34 -0000 Received: from b01ledav003.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp22034.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id wAC3OXMI62849130 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 12 Nov 2018 03:24:33 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 92E31B2519; Mon, 12 Nov 2018 03:19:25 +0000 (GMT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 59E0FB2513; Mon, 12 Nov 2018 03:19:15 +0000 (GMT) Received: from paulmck-ThinkPad-W541 (unknown [9.85.207.24]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Mon, 12 Nov 2018 03:19:15 +0000 (GMT) Received: by paulmck-ThinkPad-W541 (Postfix, from userid 1000) id A27C616C39E4; Sun, 11 Nov 2018 19:19:16 -0800 (PST) Date: Sun, 11 Nov 2018 19:19:16 -0800 From: "Paul E. McKenney" To: Masami Hiramatsu Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, "Naveen N. Rao" , Anil S Keshavamurthy , "David S. Miller" Subject: Re: [PATCH tip/core/rcu 20/41] kprobes: eplace synchronize_sched() with synchronize_rcu() Reply-To: paulmck@linux.ibm.com References: <20181111194104.GA4787@linux.ibm.com> <20181111194410.6368-20-paulmck@linux.ibm.com> <20181112120048.12b3fb7549f4b292fea1eefd@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181112120048.12b3fb7549f4b292fea1eefd@kernel.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 18111203-0052-0000-0000-0000035465EE X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00010030; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000270; SDB=6.01116164; UDB=6.00578824; IPR=6.00896273; MB=3.00024116; MTD=3.00000008; XFM=3.00000015; UTC=2018-11-12 03:24:39 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18111203-0053-0000-0000-00005EBC075B Message-Id: <20181112031916.GF4170@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-11-12_02:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1811120030 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 12, 2018 at 12:00:48PM +0900, Masami Hiramatsu wrote: > On Sun, 11 Nov 2018 11:43:49 -0800 > "Paul E. McKenney" 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)? Yes, but only as of this merge window. See this commit: 3e3100989869 ("rcu: Defer reporting RCU-preempt quiescent states when disabled") Don't try this in v4.19 or earlier, but v4.20 and later is OK. ;-) Thanx, Paul > If so, I agree with these changes. > > Thank you, > > > > > Signed-off-by: Paul E. McKenney > > Cc: "Naveen N. Rao" > > Cc: Anil S Keshavamurthy > > Cc: "David S. Miller" > > Cc: Masami Hiramatsu > > --- > > 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 >