From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DD88FC433E0 for ; Tue, 19 May 2020 20:20:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BC25A2070A for ; Tue, 19 May 2020 20:20:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728115AbgESUUq (ORCPT ); Tue, 19 May 2020 16:20:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55552 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726595AbgESUUo (ORCPT ); Tue, 19 May 2020 16:20:44 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DAC5EC08C5C0; Tue, 19 May 2020 13:20:43 -0700 (PDT) Received: from localhost ([127.0.0.1] helo=flow.W.breakpoint.cc) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1jb8ig-00012c-Sv; Tue, 19 May 2020 22:20:10 +0200 From: Sebastian Andrzej Siewior To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , Ingo Molnar , Steven Rostedt , Will Deacon , Thomas Gleixner , "Paul E . McKenney" , Linus Torvalds , Mike Galbraith , Evgeniy Polyakov , netdev@vger.kernel.org, Sebastian Andrzej Siewior Subject: [PATCH 6/8] connector/cn_proc: Protect send_msg() with a local lock Date: Tue, 19 May 2020 22:19:10 +0200 Message-Id: <20200519201912.1564477-7-bigeasy@linutronix.de> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200519201912.1564477-1-bigeasy@linutronix.de> References: <20200519201912.1564477-1-bigeasy@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Mike Galbraith send_msg() disables preemption to avoid out-of-order messages. As the code inside the preempt disabled section acquires regular spinlocks, which are converted to 'sleeping' spinlocks on a PREEMPT_RT kernel and eventually calls into a memory allocator, this conflicts with the RT semantics. Convert it to a local_lock which allows RT kernels to substitute them with a real per CPU lock. On non RT kernels this maps to preempt_disable() as before. No functional change. [bigeasy: Patch description] Cc: Evgeniy Polyakov Cc: netdev@vger.kernel.org Signed-off-by: Mike Galbraith Signed-off-by: Sebastian Andrzej Siewior --- drivers/connector/cn_proc.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c index d58ce664da843..055b0c86a0693 100644 --- a/drivers/connector/cn_proc.c +++ b/drivers/connector/cn_proc.c @@ -18,6 +18,7 @@ #include =20 #include +#include =20 /* * Size of a cn_msg followed by a proc_event structure. Since the @@ -40,10 +41,11 @@ static struct cb_id cn_proc_event_id =3D { CN_IDX_PROC,= CN_VAL_PROC }; =20 /* proc_event_counts is used as the sequence number of the netlink message= */ static DEFINE_PER_CPU(__u32, proc_event_counts) =3D { 0 }; +static DEFINE_LOCAL_LOCK(send_msg_lock); =20 static inline void send_msg(struct cn_msg *msg) { - preempt_disable(); + local_lock(send_msg_lock); =20 msg->seq =3D __this_cpu_inc_return(proc_event_counts) - 1; ((struct proc_event *)msg->data)->cpu =3D smp_processor_id(); @@ -56,7 +58,7 @@ static inline void send_msg(struct cn_msg *msg) */ cn_netlink_send(msg, 0, CN_IDX_PROC, GFP_NOWAIT); =20 - preempt_enable(); + local_unlock(send_msg_lock); } =20 void proc_fork_connector(struct task_struct *task) --=20 2.26.2