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=-8.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 CCB59C2BB48 for ; Thu, 10 Dec 2020 02:30:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8C46223C43 for ; Thu, 10 Dec 2020 02:30:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728591AbgLJCa0 (ORCPT ); Wed, 9 Dec 2020 21:30:26 -0500 Received: from m43-15.mailgun.net ([69.72.43.15]:32394 "EHLO m43-15.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726194AbgLJCa0 (ORCPT ); Wed, 9 Dec 2020 21:30:26 -0500 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1607567402; h=Message-ID: References: In-Reply-To: Subject: Cc: To: From: Date: Content-Transfer-Encoding: Content-Type: MIME-Version: Sender; bh=40LTHRRiwpmO9r5XbxQfhELyIQmQt7dPKdao3F8ry0I=; b=lO+QrZHjjHh01dWH9iEVvqY6c3q/1zYfOD0s293VBO25TT0/Dg1lzcaurVKfmfK0A77RMnWC SApSiRSbedqNKkq1XNkBnHEBv0EBjulqjZcug4Ao7kCDmJJxpfoI7T8TBbWBMwrrQJE8of0a 5qxXnaZvWWtmISDdkrsUGXEomT4= X-Mailgun-Sending-Ip: 69.72.43.15 X-Mailgun-Sid: WyI3YTAwOSIsICJsaW51eC13aXJlbGVzc0B2Z2VyLmtlcm5lbC5vcmciLCAiYmU5ZTRhIl0= Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n07.prod.us-east-1.postgun.com with SMTP id 5fd1881189cdd9db9084418b (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Thu, 10 Dec 2020 02:29:37 GMT Sender: wgong=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 55EB3C43462; Thu, 10 Dec 2020 02:29:36 +0000 (UTC) Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: wgong) by smtp.codeaurora.org (Postfix) with ESMTPSA id A60FCC433C6; Thu, 10 Dec 2020 02:29:35 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Thu, 10 Dec 2020 10:29:35 +0800 From: Wen Gong To: Ben Greear Cc: Kalle Valo , linux-wireless@vger.kernel.org, ath10k@lists.infradead.org Subject: Re: [PATCH v3] ath10k: add flag to protect napi operation to avoid dead loop hang In-Reply-To: <8a97f5ba-8eba-d61b-4c92-bdfd08d388ee@candelatech.com> References: <1598617348-2325-1-git-send-email-wgong@codeaurora.org> <87d02x1rqb.fsf@codeaurora.org> <010101746bd17881-819242de-7cbb-4df3-93e2-59473d281155-000000@us-west-2.amazonses.com> <87r1nzbadn.fsf@codeaurora.org> <8a97f5ba-8eba-d61b-4c92-bdfd08d388ee@candelatech.com> Message-ID: X-Sender: wgong@codeaurora.org User-Agent: Roundcube Webmail/1.3.9 Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org On 2020-12-09 23:00, Ben Greear wrote: > On 12/9/20 1:24 AM, Kalle Valo wrote: >> Wen Gong writes: >> >>> On 2020-09-08 00:22, Kalle Valo wrote: >>> >>>> Just like with the recent firmware restart patch, isn't >>>> ar->napi_enabled >>>> racy? Wouldn't test_and_set_bit() and test_and_clear_bit() be safer? >>>> >>>> Or are we holding a lock? But then that should be documented with >>>> lockdep_assert_held(). >>> >>> yes, ath10k_hif_start is only called from ath10k_core_start, it has >>> "lockdep_assert_held(&ar->conf_mutex)", and ath10k_hif_stop is only >>> called from ath10k_core_stop, it also has >>> "lockdep_assert_held(&ar->conf_mutex)". then it will not 2 thread >>> both >>> enter ath10k_hif_start/ath10k_hif_stop meanwhile. >> >> Ok, but every function depending on a lock being held should still >> call >> lockdep_assert_held(), that way we can catch the bug if locking >> changes >> later. So it's not enough that ath10k_core_stop() has >> lockdep_assert_held(), also these napi functions should have it. >> >> I actually decided to switch using ATH10K_FLAG_NAPI_ENABLED with >> set_bit() & co, simpler locking that way and no lockdep_assert_held() >> needed anymore. Please check my changes in the pending branch, I have >> only compile tested them: >> >> https://git.kernel.org/pub/scm/linux/kernel/git/kvalo/ath.git/commit/?h=pending&id=e0a466d296bd862080f7796b41349f9f586272c9 >> > > Why do you not need locking? You can't just check a bit is set and > then do work and set > it later without locking, two concurrent CPU threads can pass the > first check and both get into > the logic below it? > maybe because which I said before: ath10k_hif_start is only called from ath10k_core_start, it has "lockdep_assert_held(&ar->conf_mutex)", and ath10k_hif_stop is only called from ath10k_core_stop, it also has "lockdep_assert_held(&ar->conf_mutex)". then it will not 2 thread both enter ath10k_hif_start/ath10k_hif_stop meanwhile. > Thanks, > Ben From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from so254-31.mailgun.net ([198.61.254.31]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1knBi6-0007EF-Tb for ath10k@lists.infradead.org; Thu, 10 Dec 2020 02:29:40 +0000 MIME-Version: 1.0 Date: Thu, 10 Dec 2020 10:29:35 +0800 From: Wen Gong Subject: Re: [PATCH v3] ath10k: add flag to protect napi operation to avoid dead loop hang In-Reply-To: <8a97f5ba-8eba-d61b-4c92-bdfd08d388ee@candelatech.com> References: <1598617348-2325-1-git-send-email-wgong@codeaurora.org> <87d02x1rqb.fsf@codeaurora.org> <010101746bd17881-819242de-7cbb-4df3-93e2-59473d281155-000000@us-west-2.amazonses.com> <87r1nzbadn.fsf@codeaurora.org> <8a97f5ba-8eba-d61b-4c92-bdfd08d388ee@candelatech.com> Message-ID: List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "ath10k" Errors-To: ath10k-bounces+kvalo=adurom.com@lists.infradead.org To: Ben Greear Cc: linux-wireless@vger.kernel.org, ath10k@lists.infradead.org, Kalle Valo On 2020-12-09 23:00, Ben Greear wrote: > On 12/9/20 1:24 AM, Kalle Valo wrote: >> Wen Gong writes: >> >>> On 2020-09-08 00:22, Kalle Valo wrote: >>> >>>> Just like with the recent firmware restart patch, isn't >>>> ar->napi_enabled >>>> racy? Wouldn't test_and_set_bit() and test_and_clear_bit() be safer? >>>> >>>> Or are we holding a lock? But then that should be documented with >>>> lockdep_assert_held(). >>> >>> yes, ath10k_hif_start is only called from ath10k_core_start, it has >>> "lockdep_assert_held(&ar->conf_mutex)", and ath10k_hif_stop is only >>> called from ath10k_core_stop, it also has >>> "lockdep_assert_held(&ar->conf_mutex)". then it will not 2 thread >>> both >>> enter ath10k_hif_start/ath10k_hif_stop meanwhile. >> >> Ok, but every function depending on a lock being held should still >> call >> lockdep_assert_held(), that way we can catch the bug if locking >> changes >> later. So it's not enough that ath10k_core_stop() has >> lockdep_assert_held(), also these napi functions should have it. >> >> I actually decided to switch using ATH10K_FLAG_NAPI_ENABLED with >> set_bit() & co, simpler locking that way and no lockdep_assert_held() >> needed anymore. Please check my changes in the pending branch, I have >> only compile tested them: >> >> https://git.kernel.org/pub/scm/linux/kernel/git/kvalo/ath.git/commit/?h=pending&id=e0a466d296bd862080f7796b41349f9f586272c9 >> > > Why do you not need locking? You can't just check a bit is set and > then do work and set > it later without locking, two concurrent CPU threads can pass the > first check and both get into > the logic below it? > maybe because which I said before: ath10k_hif_start is only called from ath10k_core_start, it has "lockdep_assert_held(&ar->conf_mutex)", and ath10k_hif_stop is only called from ath10k_core_stop, it also has "lockdep_assert_held(&ar->conf_mutex)". then it will not 2 thread both enter ath10k_hif_start/ath10k_hif_stop meanwhile. > Thanks, > Ben _______________________________________________ ath10k mailing list ath10k@lists.infradead.org http://lists.infradead.org/mailman/listinfo/ath10k