From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx01.omp.ru (mx01.omp.ru [90.154.21.10]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8551820EE; Sun, 14 Jan 2024 12:38:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=omp.ru Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=omp.ru Received: from [192.168.1.105] (178.176.75.181) by msexch01.omp.ru (10.188.4.12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id 15.2.1258.12; Sun, 14 Jan 2024 15:22:47 +0300 Subject: Re: [PATCH net-next v3 17/19] net: ravb: Return cached statistics if the interface is down To: claudiu beznea , , , , , , , , CC: , , , , Claudiu Beznea References: <20240105082339.1468817-1-claudiu.beznea.uj@bp.renesas.com> <20240105082339.1468817-18-claudiu.beznea.uj@bp.renesas.com> From: Sergey Shtylyov Organization: Open Mobile Platform Message-ID: <28754087-8685-015e-7e8a-d8c3ed26930c@omp.ru> Date: Sun, 14 Jan 2024 15:22:47 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: msexch01.omp.ru (10.188.4.12) To msexch01.omp.ru (10.188.4.12) X-KSE-ServerInfo: msexch01.omp.ru, 9 X-KSE-AntiSpam-Interceptor-Info: scan successful X-KSE-AntiSpam-Version: 6.1.0, Database issued on: 01/14/2024 12:05:15 X-KSE-AntiSpam-Status: KAS_STATUS_NOT_DETECTED X-KSE-AntiSpam-Method: none X-KSE-AntiSpam-Rate: 59 X-KSE-AntiSpam-Info: Lua profiles 182622 [Jan 14 2024] X-KSE-AntiSpam-Info: Version: 6.1.0.3 X-KSE-AntiSpam-Info: Envelope from: s.shtylyov@omp.ru X-KSE-AntiSpam-Info: LuaCore: 7 0.3.7 6d6bf5bd8eea7373134f756a2fd73e9456bb7d1a X-KSE-AntiSpam-Info: {rep_avail} X-KSE-AntiSpam-Info: {Tracking_from_domain_doesnt_match_to} X-KSE-AntiSpam-Info: {relay has no DNS name} X-KSE-AntiSpam-Info: {SMTP from is not routable} X-KSE-AntiSpam-Info: {Found in DNSBL: 178.176.75.181 in (user) b.barracudacentral.org} X-KSE-AntiSpam-Info: omp.ru:7.1.1;127.0.0.199:7.1.2;d41d8cd98f00b204e9800998ecf8427e.com:7.1.1 X-KSE-AntiSpam-Info: ApMailHostAddress: 178.176.75.181 X-KSE-AntiSpam-Info: {DNS response errors} X-KSE-AntiSpam-Info: Rate: 59 X-KSE-AntiSpam-Info: Status: not_detected X-KSE-AntiSpam-Info: Method: none X-KSE-AntiSpam-Info: Auth:dmarc=temperror header.from=omp.ru;spf=temperror smtp.mailfrom=omp.ru;dkim=none X-KSE-Antiphishing-Info: Clean X-KSE-Antiphishing-ScanningType: Heuristic X-KSE-Antiphishing-Method: None X-KSE-Antiphishing-Bases: 01/14/2024 12:10:00 X-KSE-Antivirus-Interceptor-Info: scan successful X-KSE-Antivirus-Info: Clean, bases: 1/14/2024 10:56:00 AM X-KSE-Attachment-Filter-Triggered-Rules: Clean X-KSE-Attachment-Filter-Triggered-Filters: Clean X-KSE-BulkMessagesFiltering-Scan-Result: InTheLimit On 1/10/24 4:17 PM, claudiu beznea wrote: [...] >>> From: Claudiu Beznea >>> >>> Return the cached statistics in case the interface is down. There should be >>> no drawback to this, as cached statistics are updated in ravb_close(). >>> >>> The commit prepares the code for the addition of runtime PM support. >>> >>> Suggested-by: Sergey Shtylyov >>> Signed-off-by: Claudiu Beznea >> [...] >> >>> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c >>> index 76035afd4054..168b6208db37 100644 >>> --- a/drivers/net/ethernet/renesas/ravb_main.c >>> +++ b/drivers/net/ethernet/renesas/ravb_main.c >>> @@ -2117,6 +2117,9 @@ static struct net_device_stats *ravb_get_stats(struct net_device *ndev) >>> const struct ravb_hw_info *info = priv->info; >>> struct net_device_stats *nstats, *stats0, *stats1; >>> >>> + if (!(ndev->flags & IFF_UP)) >> >> Well, I guess it's OK to read the counters in the reset mode... BUT >> won't this race with pm_runtime_put_autosuspend() when its call gets added >> to ravb_close()? > > I re-checked it and, yes, this is true. A sync runtime suspend would be > better here. But, as of my current investigation, even with this No, the sync form of the RPM call won't fix the race... > ravb_get_stats() can still race with ravb_open()/ravb_close() as they are > called though different locking scheme (ravb_open()/ravb_close() is called > with rtnl locked while ravb_get_stats() can be called only with > dev_base_lock rwlock locked for reading). > > A mutex in the driver should to help with this. Why don't you want to mimic what the sh_eth driver does? > Thank you, > Claudiu Beznea [...] MBR, Sergey