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Mon, 21 Sep 2026 16:12:57 -0400 X-MC-Unique: XVPIjv8BPgi4PlY_UW2Ymw-1 X-Mimecast-MFC-AGG-ID: XVPIjv8BPgi4PlY_UW2Ymw_1790021571 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 686E71828AFC; Mon, 21 Sep 2026 20:12:50 +0000 (UTC) Received: from fedora (headnet03.pony-001.prod.iad2.dc.redhat.com [10.2.32.114]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id BCA221956042; Mon, 21 Sep 2026 20:12:33 +0000 (UTC) Received: by fedora (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 21 Sep 2026 22:12:50 +0200 (CEST) Date: Mon, 21 Sep 2026 22:12:32 +0200 From: Oleg Nesterov To: Ye Liu Cc: Andrew Morton , Ye Liu , Michal Hocko , Lorenzo Stoakes , Gregory Price , SJ Park , peterz@infradead.org, paulmck@kernel.org, mingo@redhat.com, rostedt@goodmis.org, jpoimboe@kernel.org, mic@digikod.net, tglx@kernel.org, david@kernel.org, linmiaohe@huawei.com, nao.horiguchi@gmail.com, rafael@kernel.org, gnoack3000@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, rcu@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-security-module@vger.kernel.org, rientjes@google.com, shakeel.butt@linux.dev, xu.xin16@zte.com.cn, chengming.zhou@linux.dev, will@kernel.org, boqun@kernel.org, frederic@kernel.org, neeraj.upadhyay@kernel.org, joelagnelf@nvidia.com, josh@joshtriplett.org, urezki@gmail.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, tony.luck@intel.com, reinette.chatre@intel.com, x86@kernel.org, paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com, pavel@kernel.org, lance.yang@linux.dev, mhiramat@kernel.org, pmladek@suse.com, longman@redhat.com, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, qiang.zhang@linux.dev, dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kprateek.nayak@amd.com, mark.rutland@arm.com, Dave.Martin@arm.com, james.morse@arm.com, babu.moger@amd.com Subject: Re: [PATCH v4 14/15] lib: convert process iterator to for_each_process_rculock Message-ID: References: <20260921092101.89285-1-ye.liu@linux.dev> <20260921093311.104814-1-ye.liu@linux.dev> MIME-Version: 1.0 In-Reply-To: <20260921093311.104814-1-ye.liu@linux.dev> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: nZxuTCjU4QOrEY-7yMox4Y0IvN_2uhPxH6LwQWh7sTc_1790021571 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 0AADD40004 X-Stat-Signature: gadc56rdonf8eops61ycjnihk6effyz5 X-HE-Tag: 1790021582-135254 X-HE-Meta: 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 q1UnyPR7 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 09/21, Ye Liu wrote: > > diff --git a/lib/is_single_threaded.c b/lib/is_single_threaded.c > index 8c98b20bfc41..4e7fe85454ab 100644 > --- a/lib/is_single_threaded.c > +++ b/lib/is_single_threaded.c > @@ -26,8 +26,7 @@ bool current_is_single_threaded(void) > return true; > > ret = false; > - rcu_read_lock(); > - for_each_process(p) { > + for_each_process_rculock(p) { > if (unlikely(p->flags & PF_KTHREAD)) > continue; > if (unlikely(p == task->group_leader)) > @@ -48,7 +47,5 @@ bool current_is_single_threaded(void) > } > ret = true; > found: > - rcu_read_unlock(); > - Reviewed-by: Oleg Nesterov but I think that the "found" label and "int ret" can now be removed, the for_each_thread() loop can just do ... if (unlikely(t->mm == mm)) return false; and current_is_single_threaded() can simply return true after the main for_each_process_rculock() loop. But again, I agree with this patch, it looks simple and "obviously correct". Even if I am right, the simplifications above need a separate change. Oleg.