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[209.132.180.67]) by mx.google.com with ESMTP id a5si8330500oie.17.2020.01.14.10.24.56; Tue, 14 Jan 2020 10:25:07 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728797AbgANSYI (ORCPT + 99 others); Tue, 14 Jan 2020 13:24:08 -0500 Received: from mga11.intel.com ([192.55.52.93]:23319 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728761AbgANSYH (ORCPT ); Tue, 14 Jan 2020 13:24:07 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 14 Jan 2020 10:24:04 -0800 X-IronPort-AV: E=Sophos;i="5.70,319,1574150400"; d="scan'208";a="213424198" Received: from ddalessa-mobl.amr.corp.intel.com (HELO [10.254.201.179]) ([10.254.201.179]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-SHA; 14 Jan 2020 10:24:02 -0800 Subject: Re: [PATCH 1/3] infiniband: hw: hfi1: verbs.c: Use built-in RCU list checking From: Dennis Dalessandro To: Jason Gunthorpe , madhuparnabhowmik04@gmail.com Cc: mike.marciniszyn@intel.com, paulmck@kernel.org, joel@joelfernandes.org, frextrite@gmail.com, linux-kernel-mentees@lists.linuxfoundation.org, rcu@vger.kernel.org, linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org References: <20200114162345.19995-1-madhuparnabhowmik04@gmail.com> <20200114165740.GB22037@ziepe.ca> <74adec84-ec5b-ea1b-7adf-3f8608838259@intel.com> Message-ID: <25133367-6544-d0af-ae30-5178909748b1@intel.com> Date: Tue, 14 Jan 2020 13:24:00 -0500 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: <74adec84-ec5b-ea1b-7adf-3f8608838259@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/14/2020 12:00 PM, Dennis Dalessandro wrote: > On 1/14/2020 11:57 AM, Jason Gunthorpe wrote: >> On Tue, Jan 14, 2020 at 09:53:45PM +0530, >> madhuparnabhowmik04@gmail.com wrote: >>> From: Madhuparna Bhowmik >>> >>> list_for_each_entry_rcu has built-in RCU and lock checking. >>> Pass cond argument to list_for_each_entry_rcu. >>> >>> Signed-off-by: Madhuparna Bhowmik >>>   drivers/infiniband/hw/hfi1/verbs.c | 2 +- >>>   1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/drivers/infiniband/hw/hfi1/verbs.c >>> b/drivers/infiniband/hw/hfi1/verbs.c >>> index 089e201d7550..22f2d4fd2577 100644 >>> +++ b/drivers/infiniband/hw/hfi1/verbs.c >>> @@ -515,7 +515,7 @@ static inline void hfi1_handle_packet(struct >>> hfi1_packet *packet, >>>                          opa_get_lid(packet->dlid, 9B)); >>>           if (!mcast) >>>               goto drop; >>> -        list_for_each_entry_rcu(p, &mcast->qp_list, list) { >>> +        list_for_each_entry_rcu(p, &mcast->qp_list, list, >>> lockdep_is_held(&(ibp->rvp.lock))) { >> >> Okay, this looks reasonable >> >> Mike, Dennis, is this the right lock to test? >> > > I'm looking at that right now actually, I don't think this is correct. > Wanted to talk to Mike before I send a response though. > > -Denny That's definitely going to throw a ton of lock dep messages. It's not really the right lock either. Instead what we probably need to do is what we do in the non-multicast part of the code and take the rcu_read_lock(). I'd say hold off on this and we'll fix it right. Same goes for the qib one. The rdmavt one though looks to be OK. I'll give it a test. -Denny