From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from Chamillionaire.breakpoint.cc (Chamillionaire.breakpoint.cc [91.216.245.30]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0554A1DFD1; Wed, 17 Jan 2024 11:47:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.216.245.30 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705492055; cv=none; b=UH7ghQo/AM56xjjwlhY16d1Bbeoib+Hgttnxx+xvNFbd70Gj/NphU8aTFcU5dtQwyIiTAh+2yU5cr0SpG43dEmM7yCu5BGI4CoxsBYi2/zLkmF+Syt5HeZS3OMsmOXXGsh/VdsJo+Xoha95JRY3UT7basoUce4OJN9lFCQKQpiM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705492055; c=relaxed/simple; bh=kvkTR7iTyZVPJBT9Sqjw0z5+Ipc3TcSsE7D3hjrE/E4=; h=Received:Date:From:To:Cc:Subject:Message-ID:References: MIME-Version:Content-Type:Content-Disposition:In-Reply-To: User-Agent; b=q6ko/VZy9AJOh7bCGu0SMhxo9SYpV7mrpmrlwxU6nXKDs1xvUu55JJ+LH71Tisb3Sq2AiTMF4LtAxHu9bvShiGN98gRJvIHoRHS1vPp+VA0+4kWiZVgxyomw5R9qzjKiEUbcusCOaMTgrsVFdOwrEFciNbNJHawuPQEOh0omcmo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=strlen.de; spf=pass smtp.mailfrom=strlen.de; arc=none smtp.client-ip=91.216.245.30 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=strlen.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=strlen.de Received: from fw by Chamillionaire.breakpoint.cc with local (Exim 4.92) (envelope-from ) id 1rQ4O1-00035J-2U; Wed, 17 Jan 2024 12:47:13 +0100 Date: Wed, 17 Jan 2024 12:47:13 +0100 From: Florian Westphal To: wangkeqi Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, wangkeqi , kernel test robot , fengwei.yin@intel.com Subject: Re: [PATCH net v2] connector: Change the judgment conditions for clearing proc_event_num_listeners Message-ID: <20240117114713.GA11468@breakpoint.cc> References: <20240116015753.209781-1-wangkeqi_chris@163.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240116015753.209781-1-wangkeqi_chris@163.com> User-Agent: Mutt/1.10.1 (2018-07-13) wangkeqi wrote: > From: wangkeqi > > It is inaccurate to judge whether proc_event_num_listeners is > cleared by cn_netlink_send_mult returning -ESRCH. > In the case of stress-ng netlink-proc, -ESRCH will always be returned, > because netlink_broadcast_filtered will return -ESRCH, > which may cause stress-ng netlink-proc performance degradation. > Therefore, the judgment condition is modified to whether > there is a listener. > > Reported-by: kernel test robot > Closes: https://lore.kernel.org/oe-lkp/202401112259.b23a1567-oliver.sang@intel.com > Fixes: c46bfba133 ("connector: Fix proc_event_num_listeners count not cleared") > Signed-off-by: wangkeqi > Cc: fengwei.yin@intel.com > --- > drivers/connector/cn_proc.c | 6 ++++-- > drivers/connector/connector.c | 6 ++++++ > include/linux/connector.h | 1 + > 3 files changed, 11 insertions(+), 2 deletions(-) > > diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c > index 3d5e6d705..b09f74ed3 100644 > --- a/drivers/connector/cn_proc.c > +++ b/drivers/connector/cn_proc.c > @@ -108,8 +108,10 @@ static inline void send_msg(struct cn_msg *msg) > filter_data[1] = 0; > } > > - if (cn_netlink_send_mult(msg, msg->len, 0, CN_IDX_PROC, GFP_NOWAIT, > - cn_filter, (void *)filter_data) == -ESRCH) > + if (netlink_has_listeners(get_cdev_nls(), CN_IDX_PROC)) > + cn_netlink_send_mult(msg, msg->len, 0, CN_IDX_PROC, GFP_NOWAIT, > + cn_filter, (void *)filter_data); > + else > atomic_set(&proc_event_num_listeners, 0); How is that serialized vs. cn_proc_mcast_ctl? 1. netlink_has_listeners() returns false 2. other core handles PROC_CN_MCAST_LISTEN, atomic_inc called 3. This core (re)sets counter to 0, but there are listeners, so all functions that do if (atomic_read(&proc_event_num_listeners) < 1) return; will not get enabled/remain disabled. Probably better to add cn_netlink_has_listeners() function and use that instead of the (inaccurate) counter?