From patchwork Wed May 27 20:11:17 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 1299203 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=linutronix.de Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 49XMRz5KMbz9sSp for ; Thu, 28 May 2020 06:11:59 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728767AbgE0UL4 (ORCPT ); Wed, 27 May 2020 16:11:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41512 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728395AbgE0ULz (ORCPT ); Wed, 27 May 2020 16:11:55 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7FA00C05BD1E; Wed, 27 May 2020 13:11:55 -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 1je2Oc-0005ku-9X; Wed, 27 May 2020 22:11:26 +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 , Matthew Wilcox , Mike Galbraith , Evgeniy Polyakov , netdev@vger.kernel.org, Sebastian Andrzej Siewior Subject: [PATCH v3 5/7] connector/cn_proc: Protect send_msg() with a local lock Date: Wed, 27 May 2020 22:11:17 +0200 Message-Id: <20200527201119.1692513-6-bigeasy@linutronix.de> X-Mailer: git-send-email 2.27.0.rc0 In-Reply-To: <20200527201119.1692513-1-bigeasy@linutronix.de> References: <20200527201119.1692513-1-bigeasy@linutronix.de> MIME-Version: 1.0 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@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 | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-) diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c index d58ce664da843..646ad385e4904 100644 --- a/drivers/connector/cn_proc.c +++ b/drivers/connector/cn_proc.c @@ -18,6 +18,7 @@ #include #include +#include /* * Size of a cn_msg followed by a proc_event structure. Since the @@ -38,25 +39,31 @@ static inline struct cn_msg *buffer_to_cn_msg(__u8 *buffer) static atomic_t proc_event_num_listeners = ATOMIC_INIT(0); static struct cb_id cn_proc_event_id = { CN_IDX_PROC, CN_VAL_PROC }; -/* proc_event_counts is used as the sequence number of the netlink message */ -static DEFINE_PER_CPU(__u32, proc_event_counts) = { 0 }; +/* local_event.count is used as the sequence number of the netlink message */ +struct local_event { + local_lock_t lock; + __u32 count; +}; +static DEFINE_PER_CPU(struct local_event, local_event) = { + .lock = INIT_LOCAL_LOCK(lock), +}; static inline void send_msg(struct cn_msg *msg) { - preempt_disable(); + local_lock(&local_event.lock); - msg->seq = __this_cpu_inc_return(proc_event_counts) - 1; + msg->seq = __this_cpu_inc_return(local_event.count) - 1; ((struct proc_event *)msg->data)->cpu = smp_processor_id(); /* - * Preemption remains disabled during send to ensure the messages are - * ordered according to their sequence numbers. + * local_lock() disables preemption during send to ensure the messages + * are ordered according to their sequence numbers. * * If cn_netlink_send() fails, the data is not sent. */ cn_netlink_send(msg, 0, CN_IDX_PROC, GFP_NOWAIT); - preempt_enable(); + local_unlock(&local_event.lock); } void proc_fork_connector(struct task_struct *task)