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 1085AC4361B for ; Wed, 9 Dec 2020 09:25:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CF51F23B79 for ; Wed, 9 Dec 2020 09:25:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729021AbgLIJZD (ORCPT ); Wed, 9 Dec 2020 04:25:03 -0500 Received: from m43-15.mailgun.net ([69.72.43.15]:12356 "EHLO m43-15.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728890AbgLIJZC (ORCPT ); Wed, 9 Dec 2020 04:25:02 -0500 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1607505878; h=Content-Type: MIME-Version: Message-ID: In-Reply-To: Date: References: Subject: Cc: To: From: Sender; bh=T9Vsn2MPWfR4OqdEnu3EaKEtE2FLT5+vaI23XMtdI7Q=; b=pXdlKSm45e4zB32h/cxz8YQ9uhK9CtHpjVAyv8icwXwLFd2cJN7kgPTjw8ugdDGWjQFrYpO7 tc77guD7Ymq3KHlE1bt6bER/qLN82+fTIRVmznXgbCI8Zhcwca05hVxbVx7ms7IyemUF5SWQ /IS2wAsFis/vcJaO7V/35HsL4/I= 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-n03.prod.us-west-2.postgun.com with SMTP id 5fd097b8d5b4c78a8f2637fe (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Wed, 09 Dec 2020 09:24:08 GMT Sender: kvalo=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 1216AC43462; Wed, 9 Dec 2020 09:24:08 +0000 (UTC) Received: from potku.adurom.net (88-114-240-156.elisa-laajakaista.fi [88.114.240.156]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: kvalo) by smtp.codeaurora.org (Postfix) with ESMTPSA id 74354C433C6; Wed, 9 Dec 2020 09:24:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 74354C433C6 Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=fail smtp.mailfrom=kvalo@codeaurora.org From: Kalle Valo To: Wen Gong Cc: 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 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> Date: Wed, 09 Dec 2020 11:24:04 +0200 In-Reply-To: <010101746bd17881-819242de-7cbb-4df3-93e2-59473d281155-000000@us-west-2.amazonses.com> (Wen Gong's message of "Tue, 8 Sep 2020 03:45:24 +0000") Message-ID: <87r1nzbadn.fsf@codeaurora.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org 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 -- https://patchwork.kernel.org/project/linux-wireless/list/ https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches 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 1kmvhi-0002Pr-IT for ath10k@lists.infradead.org; Wed, 09 Dec 2020 09:24:11 +0000 From: Kalle Valo Subject: Re: [PATCH v3] ath10k: add flag to protect napi operation to avoid dead loop hang 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> Date: Wed, 09 Dec 2020 11:24:04 +0200 In-Reply-To: <010101746bd17881-819242de-7cbb-4df3-93e2-59473d281155-000000@us-west-2.amazonses.com> (Wen Gong's message of "Tue, 8 Sep 2020 03:45:24 +0000") Message-ID: <87r1nzbadn.fsf@codeaurora.org> MIME-Version: 1.0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "ath10k" Errors-To: ath10k-bounces+kvalo=adurom.com@lists.infradead.org To: Wen Gong Cc: linux-wireless@vger.kernel.org, ath10k@lists.infradead.org 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 -- https://patchwork.kernel.org/project/linux-wireless/list/ https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches _______________________________________________ ath10k mailing list ath10k@lists.infradead.org http://lists.infradead.org/mailman/listinfo/ath10k