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[51.6.142.41]) by smtp.gmail.com with ESMTPSA id r6sm25367610wrq.92.2020.01.15.05.56.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Jan 2020 05:56:33 -0800 (PST) Date: Wed, 15 Jan 2020 13:56:31 +0000 From: Wei Liu To: madhuparnabhowmik04@gmail.com Message-ID: <20200115135631.edr2nrfkycppxcku@debian> References: <20200115124129.5684-1-madhuparnabhowmik04@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200115124129.5684-1-madhuparnabhowmik04@gmail.com> User-Agent: NeoMutt/20180716 Cc: wei.liu@kernel.org, paulmck@kernel.org, paul@xen.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, joel@joelfernandes.org, xen-devel@lists.xenproject.org, linux-kernel-mentees@lists.linuxfoundation.org, davem@davemloft.net Subject: Re: [Linux-kernel-mentees] [PATCH] net: xen-netbank: hash.c: Use built-in RCU list checking X-BeenThere: linux-kernel-mentees@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-kernel-mentees-bounces@lists.linuxfoundation.org Sender: "Linux-kernel-mentees" Thanks for the patch. There is a typo in the subject line. It should say xen-netback, not xen-netbank. On Wed, Jan 15, 2020 at 06:11:28PM +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/net/xen-netback/hash.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/xen-netback/hash.c b/drivers/net/xen-netback/hash.c > index 10d580c3dea3..30709bc9d170 100644 > --- a/drivers/net/xen-netback/hash.c > +++ b/drivers/net/xen-netback/hash.c > @@ -51,7 +51,8 @@ static void xenvif_add_hash(struct xenvif *vif, const u8 *tag, > > found = false; > oldest = NULL; > - list_for_each_entry_rcu(entry, &vif->hash.cache.list, link) { > + list_for_each_entry_rcu(entry, &vif->hash.cache.list, link, > + lockdep_is_held(&vif->hash.cache.lock)) { There are probably too many tabs here. Indentation looks wrong. The surrounding code makes it pretty clear that the lock is already held by the time list_for_each_entry_rcu is called, yet the checking involved in lockdep_is_held is not trivial, so I'm afraid I don't consider this a strict improvement over the existing code. If there is something I misunderstood, let me know. Wei. > /* Make sure we don't add duplicate entries */ > if (entry->len == len && > memcmp(entry->tag, tag, len) == 0) > @@ -102,7 +103,8 @@ static void xenvif_flush_hash(struct xenvif *vif) > > spin_lock_irqsave(&vif->hash.cache.lock, flags); > > - list_for_each_entry_rcu(entry, &vif->hash.cache.list, link) { > + list_for_each_entry_rcu(entry, &vif->hash.cache.list, link, > + lockdep_is_held(&vif->hash.cache.lock)) { > list_del_rcu(&entry->link); > vif->hash.cache.count--; > kfree_rcu(entry, rcu); > -- > 2.17.1 > _______________________________________________ Linux-kernel-mentees mailing list Linux-kernel-mentees@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees 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=-8.5 required=3.0 tests=INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 8FFE6C33CB1 for ; Wed, 15 Jan 2020 13:57:17 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6AF0924671 for ; Wed, 15 Jan 2020 13:57:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6AF0924671 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1irjA5-00076G-U1; Wed, 15 Jan 2020 13:56:45 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1irjA4-00076B-EC for xen-devel@lists.xenproject.org; Wed, 15 Jan 2020 13:56:44 +0000 X-Inumbo-ID: d7a84384-379e-11ea-b89f-bc764e2007e4 Received: from mail-wr1-f66.google.com (unknown [209.85.221.66]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id d7a84384-379e-11ea-b89f-bc764e2007e4; Wed, 15 Jan 2020 13:56:35 +0000 (UTC) Received: by mail-wr1-f66.google.com with SMTP id c14so15830841wrn.7 for ; Wed, 15 Jan 2020 05:56:35 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=UVc+vS25sl77DRieZ7fqDsmqFprVJrI4fDKBKV1QbSs=; b=O1fCXegC4IxSwSDKurobkFViN+IFM9FmbipQskGvCXHe7lvoxyDmjQIcfh7ALfjf7I mOCVOuVKfUNnW/ssbtxS7UPhkYir58QZcvqx9E7lJC9FHaLpH+j6OSgOT105WprknzGE cUGOoLKntA+e4C6uXqy2XF1hcwX8i4uaB44WTfaSb26vJ51P0LRdseY1+iC4qQt1sRmP 2yI7xsIYZVHPKIxMm+1IAUnqJpOk10gHdswd6KZbMJKWVJoLMhjfA9qPEeYYTNPVTUWE 5kuAJDhrhPyE97Kd+kAAlUpj6FW/EAhL0gXgi6cudPTLwKNPF5oU9MncTAM76joZELs5 qdGQ== X-Gm-Message-State: APjAAAUE8htwLbZ4vkyFMjiACiQneCH9CzeLbB8A/fvqyZ5qjIZZhd+C vxaVUaOqGhBCYWbtkE8/VbQ= X-Google-Smtp-Source: APXvYqyXYe4s0+Dcy7oHJR4GBgwa+hNOEdtdbuIIeeHe/ERVxkCyU9BEoy570XvbPj01KdjYPiKSMQ== X-Received: by 2002:adf:df90:: with SMTP id z16mr33198153wrl.273.1579096594676; Wed, 15 Jan 2020 05:56:34 -0800 (PST) Received: from debian (41.142.6.51.dyn.plus.net. [51.6.142.41]) by smtp.gmail.com with ESMTPSA id r6sm25367610wrq.92.2020.01.15.05.56.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Jan 2020 05:56:33 -0800 (PST) Date: Wed, 15 Jan 2020 13:56:31 +0000 From: Wei Liu To: madhuparnabhowmik04@gmail.com Message-ID: <20200115135631.edr2nrfkycppxcku@debian> References: <20200115124129.5684-1-madhuparnabhowmik04@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200115124129.5684-1-madhuparnabhowmik04@gmail.com> User-Agent: NeoMutt/20180716 Subject: Re: [Xen-devel] [PATCH] net: xen-netbank: hash.c: Use built-in RCU list checking X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: wei.liu@kernel.org, paulmck@kernel.org, paul@xen.org, netdev@vger.kernel.org, frextrite@gmail.com, linux-kernel@vger.kernel.org, joel@joelfernandes.org, xen-devel@lists.xenproject.org, linux-kernel-mentees@lists.linuxfoundation.org, davem@davemloft.net Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" VGhhbmtzIGZvciB0aGUgcGF0Y2guCgpUaGVyZSBpcyBhIHR5cG8gaW4gdGhlIHN1YmplY3QgbGlu ZS4gSXQgc2hvdWxkIHNheSB4ZW4tbmV0YmFjaywgbm90Cnhlbi1uZXRiYW5rLgoKT24gV2VkLCBK YW4gMTUsIDIwMjAgYXQgMDY6MTE6MjhQTSArMDUzMCwgbWFkaHVwYXJuYWJob3dtaWswNEBnbWFp bC5jb20gd3JvdGU6Cj4gRnJvbTogTWFkaHVwYXJuYSBCaG93bWlrIDxtYWRodXBhcm5hYmhvd21p azA0QGdtYWlsLmNvbT4KPiAKPiBsaXN0X2Zvcl9lYWNoX2VudHJ5X3JjdSBoYXMgYnVpbHQtaW4g UkNVIGFuZCBsb2NrIGNoZWNraW5nLgo+IFBhc3MgY29uZCBhcmd1bWVudCB0byBsaXN0X2Zvcl9l YWNoX2VudHJ5X3JjdS4KPiAKPiBTaWduZWQtb2ZmLWJ5OiBNYWRodXBhcm5hIEJob3dtaWsgPG1h ZGh1cGFybmFiaG93bWlrMDRAZ21haWwuY29tPgo+IC0tLQo+ICBkcml2ZXJzL25ldC94ZW4tbmV0 YmFjay9oYXNoLmMgfCA2ICsrKystLQo+ICAxIGZpbGUgY2hhbmdlZCwgNCBpbnNlcnRpb25zKCsp LCAyIGRlbGV0aW9ucygtKQo+IAo+IGRpZmYgLS1naXQgYS9kcml2ZXJzL25ldC94ZW4tbmV0YmFj ay9oYXNoLmMgYi9kcml2ZXJzL25ldC94ZW4tbmV0YmFjay9oYXNoLmMKPiBpbmRleCAxMGQ1ODBj M2RlYTMuLjMwNzA5YmM5ZDE3MCAxMDA2NDQKPiAtLS0gYS9kcml2ZXJzL25ldC94ZW4tbmV0YmFj ay9oYXNoLmMKPiArKysgYi9kcml2ZXJzL25ldC94ZW4tbmV0YmFjay9oYXNoLmMKPiBAQCAtNTEs NyArNTEsOCBAQCBzdGF0aWMgdm9pZCB4ZW52aWZfYWRkX2hhc2goc3RydWN0IHhlbnZpZiAqdmlm LCBjb25zdCB1OCAqdGFnLAo+ICAKPiAgCWZvdW5kID0gZmFsc2U7Cj4gIAlvbGRlc3QgPSBOVUxM Owo+IC0JbGlzdF9mb3JfZWFjaF9lbnRyeV9yY3UoZW50cnksICZ2aWYtPmhhc2guY2FjaGUubGlz dCwgbGluaykgewo+ICsJbGlzdF9mb3JfZWFjaF9lbnRyeV9yY3UoZW50cnksICZ2aWYtPmhhc2gu Y2FjaGUubGlzdCwgbGluaywKPiArCQkJCQkJCWxvY2tkZXBfaXNfaGVsZCgmdmlmLT5oYXNoLmNh Y2hlLmxvY2spKSB7CgpUaGVyZSBhcmUgcHJvYmFibHkgdG9vIG1hbnkgdGFicyBoZXJlLiBJbmRl bnRhdGlvbiBsb29rcyB3cm9uZy4KClRoZSBzdXJyb3VuZGluZyBjb2RlIG1ha2VzIGl0IHByZXR0 eSBjbGVhciB0aGF0IHRoZSBsb2NrIGlzIGFscmVhZHkgaGVsZApieSB0aGUgdGltZSBsaXN0X2Zv cl9lYWNoX2VudHJ5X3JjdSBpcyBjYWxsZWQsIHlldCB0aGUgY2hlY2tpbmcgaW52b2x2ZWQKaW4g bG9ja2RlcF9pc19oZWxkIGlzIG5vdCB0cml2aWFsLCBzbyBJJ20gYWZyYWlkIEkgZG9uJ3QgY29u c2lkZXIgdGhpcyBhCnN0cmljdCBpbXByb3ZlbWVudCBvdmVyIHRoZSBleGlzdGluZyBjb2RlLgoK SWYgdGhlcmUgaXMgc29tZXRoaW5nIEkgbWlzdW5kZXJzdG9vZCwgbGV0IG1lIGtub3cuCgpXZWku Cgo+ICAJCS8qIE1ha2Ugc3VyZSB3ZSBkb24ndCBhZGQgZHVwbGljYXRlIGVudHJpZXMgKi8KPiAg CQlpZiAoZW50cnktPmxlbiA9PSBsZW4gJiYKPiAgCQkgICAgbWVtY21wKGVudHJ5LT50YWcsIHRh ZywgbGVuKSA9PSAwKQo+IEBAIC0xMDIsNyArMTAzLDggQEAgc3RhdGljIHZvaWQgeGVudmlmX2Zs dXNoX2hhc2goc3RydWN0IHhlbnZpZiAqdmlmKQo+ICAKPiAgCXNwaW5fbG9ja19pcnFzYXZlKCZ2 aWYtPmhhc2guY2FjaGUubG9jaywgZmxhZ3MpOwo+ICAKPiAtCWxpc3RfZm9yX2VhY2hfZW50cnlf cmN1KGVudHJ5LCAmdmlmLT5oYXNoLmNhY2hlLmxpc3QsIGxpbmspIHsKPiArCWxpc3RfZm9yX2Vh Y2hfZW50cnlfcmN1KGVudHJ5LCAmdmlmLT5oYXNoLmNhY2hlLmxpc3QsIGxpbmssCj4gKwkJCQkJ CQlsb2NrZGVwX2lzX2hlbGQoJnZpZi0+aGFzaC5jYWNoZS5sb2NrKSkgewo+ICAJCWxpc3RfZGVs X3JjdSgmZW50cnktPmxpbmspOwo+ICAJCXZpZi0+aGFzaC5jYWNoZS5jb3VudC0tOwo+ICAJCWtm cmVlX3JjdShlbnRyeSwgcmN1KTsKPiAtLSAKPiAyLjE3LjEKPiAKCl9fX19fX19fX19fX19fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fClhlbi1kZXZlbCBtYWlsaW5nIGxpc3QKWGVu LWRldmVsQGxpc3RzLnhlbnByb2plY3Qub3JnCmh0dHBzOi8vbGlzdHMueGVucHJvamVjdC5vcmcv bWFpbG1hbi9saXN0aW5mby94ZW4tZGV2ZWw= 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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 2CB9FC33CB1 for ; 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[51.6.142.41]) by smtp.gmail.com with ESMTPSA id r6sm25367610wrq.92.2020.01.15.05.56.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Jan 2020 05:56:33 -0800 (PST) Date: Wed, 15 Jan 2020 13:56:31 +0000 From: Wei Liu To: madhuparnabhowmik04@gmail.com Cc: wei.liu@kernel.org, paul@xen.org, davem@davemloft.net, xen-devel@lists.xenproject.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, paulmck@kernel.org, joel@joelfernandes.org, frextrite@gmail.com, linux-kernel-mentees@lists.linuxfoundation.org Subject: Re: [PATCH] net: xen-netbank: hash.c: Use built-in RCU list checking Message-ID: <20200115135631.edr2nrfkycppxcku@debian> References: <20200115124129.5684-1-madhuparnabhowmik04@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200115124129.5684-1-madhuparnabhowmik04@gmail.com> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Thanks for the patch. There is a typo in the subject line. It should say xen-netback, not xen-netbank. On Wed, Jan 15, 2020 at 06:11:28PM +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/net/xen-netback/hash.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/xen-netback/hash.c b/drivers/net/xen-netback/hash.c > index 10d580c3dea3..30709bc9d170 100644 > --- a/drivers/net/xen-netback/hash.c > +++ b/drivers/net/xen-netback/hash.c > @@ -51,7 +51,8 @@ static void xenvif_add_hash(struct xenvif *vif, const u8 *tag, > > found = false; > oldest = NULL; > - list_for_each_entry_rcu(entry, &vif->hash.cache.list, link) { > + list_for_each_entry_rcu(entry, &vif->hash.cache.list, link, > + lockdep_is_held(&vif->hash.cache.lock)) { There are probably too many tabs here. Indentation looks wrong. The surrounding code makes it pretty clear that the lock is already held by the time list_for_each_entry_rcu is called, yet the checking involved in lockdep_is_held is not trivial, so I'm afraid I don't consider this a strict improvement over the existing code. If there is something I misunderstood, let me know. Wei. > /* Make sure we don't add duplicate entries */ > if (entry->len == len && > memcmp(entry->tag, tag, len) == 0) > @@ -102,7 +103,8 @@ static void xenvif_flush_hash(struct xenvif *vif) > > spin_lock_irqsave(&vif->hash.cache.lock, flags); > > - list_for_each_entry_rcu(entry, &vif->hash.cache.list, link) { > + list_for_each_entry_rcu(entry, &vif->hash.cache.list, link, > + lockdep_is_held(&vif->hash.cache.lock)) { > list_del_rcu(&entry->link); > vif->hash.cache.count--; > kfree_rcu(entry, rcu); > -- > 2.17.1 >