From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from s3.sipsolutions.net ([5.9.151.49] helo=sipsolutions.net) by bombadil.infradead.org with esmtps (Exim 4.85_2 #1 (Red Hat Linux)) id 1bjKwd-0003Xk-8E for ath10k@lists.infradead.org; Mon, 12 Sep 2016 06:42:20 +0000 Message-ID: <1473662509.4201.0.camel@sipsolutions.net> Subject: Re: [PATCH 2/3] ath10k: Grab rcu_read_lock before the txqs spinlock. From: Johannes Berg Date: Mon, 12 Sep 2016 08:41:49 +0200 In-Reply-To: <57D2CB92.3020407@candelatech.com> (sfid-20160909_164754_211937_A51918C3) References: <1471569995-10028-1-git-send-email-greearb@candelatech.com> <1471569995-10028-2-git-send-email-greearb@candelatech.com> <87k2elp53z.fsf@kamboji.qca.qualcomm.com> <57D2CB92.3020407@candelatech.com> (sfid-20160909_164754_211937_A51918C3) Mime-Version: 1.0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "ath10k" Errors-To: ath10k-bounces+kvalo=adurom.com@lists.infradead.org To: Ben Greear , "Valo, Kalle" Cc: "linux-wireless@vger.kernel.org" , "ath10k@lists.infradead.org" Cj4gPiA+IC0JcmN1X3JlYWRfdW5sb2NrKCk7Cj4gPiA+IMKgwqAJc3Bpbl91bmxvY2tfYmgoJmFy LT50eHFzX2xvY2spOwo+ID4gPiArCXJjdV9yZWFkX3VubG9jaygpOwo+ID4gCj4gPiBJJ20gbm8g UkNVIGV4cGVydCBidXQgdGhpcyBpc24ndCBtYWtpbmcgYW55IHNlbnNlLiBNYXliZSBpdCBjaGFu Z2VzCj4gPiB0aW1pbmdzIG9uIHlvdXIga2VybmVsIHNvIHRoYXQgaXQgaGlkZXMgdGhlIHJlYWwg cHJvYmxlbT8KPiAKPiBJJ20gbm90IHN1cmUgdGhpcyBmaXhlZCBhbnl0aGluZyBvciBub3QsIGl0 IGp1c3Qgc2VlbWVkIHdlaXJkIHNvIEkKPiBjaGFuZ2VkIGl0Lgo+IAo+IEkgd2FzIGhvcGluZyBz b21lb25lIHRoYXQgdW5kZXJzdG9vZCByY3UgbG9ja2luZyB3b3VsZCBjb21tZW50Li4uCj4gCgpS Q1UgaXMgbm8gImxvY2tpbmciLiBUaGUgc29vbmVyIHlvdSBnZXQgb3ZlciB0aGF0IG5vdGlvbiwg dGhlIGJldHRlci4KClRoaXMgdGhlcmVmb3JlIG1ha2Ugbm8gc2Vuc2Ugd2hhdHNvZXZlci4KCklu IGZhY3QsIHlvdSB3YW50IHRvIGtlZXAgdGhlIFJDVSBwcm90ZWN0ZWQgc2VjdGlvbiAqc21hbGwq LCBzbyBoYXZpbmcKdGhlIHNwaW5sb2NrIGluc2lkZSBodXJ0cyBvdmVyYWxsIHN5c3RlbSBwZXJm b3JtYW5jZS4KCmpvaGFubmVzCgpfX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fXwphdGgxMGsgbWFpbGluZyBsaXN0CmF0aDEwa0BsaXN0cy5pbmZyYWRlYWQub3Jn Cmh0dHA6Ly9saXN0cy5pbmZyYWRlYWQub3JnL21haWxtYW4vbGlzdGluZm8vYXRoMTBrCg== From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from s3.sipsolutions.net ([5.9.151.49]:56366 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752742AbcILGl5 (ORCPT ); Mon, 12 Sep 2016 02:41:57 -0400 Message-ID: <1473662509.4201.0.camel@sipsolutions.net> (sfid-20160912_084202_742284_FBA547D6) Subject: Re: [PATCH 2/3] ath10k: Grab rcu_read_lock before the txqs spinlock. From: Johannes Berg To: Ben Greear , "Valo, Kalle" Cc: "ath10k@lists.infradead.org" , "linux-wireless@vger.kernel.org" Date: Mon, 12 Sep 2016 08:41:49 +0200 In-Reply-To: <57D2CB92.3020407@candelatech.com> (sfid-20160909_164754_211937_A51918C3) References: <1471569995-10028-1-git-send-email-greearb@candelatech.com> <1471569995-10028-2-git-send-email-greearb@candelatech.com> <87k2elp53z.fsf@kamboji.qca.qualcomm.com> <57D2CB92.3020407@candelatech.com> (sfid-20160909_164754_211937_A51918C3) Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: > > > - rcu_read_unlock(); > > >    spin_unlock_bh(&ar->txqs_lock); > > > + rcu_read_unlock(); > > > > I'm no RCU expert but this isn't making any sense. Maybe it changes > > timings on your kernel so that it hides the real problem? > > I'm not sure this fixed anything or not, it just seemed weird so I > changed it. > > I was hoping someone that understood rcu locking would comment... > RCU is no "locking". The sooner you get over that notion, the better. This therefore make no sense whatsoever. In fact, you want to keep the RCU protected section *small*, so having the spinlock inside hurts overall system performance. johannes