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=-8.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, 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 63E06C4361B for ; Tue, 15 Dec 2020 07:57:51 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 ECFD222273 for ; Tue, 15 Dec 2020 07:57:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org ECFD222273 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=ath10k-bounces+ath10k=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:Message-ID:In-Reply-To:Date:References: Subject:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=fH7kRd1mWfgg8oxglzzIeRpqX/PIitySBiMFl8INSIE=; b=ofF+Ll3Q9hDCxWyE7KuhxAO6k 015/493ujgZqXdiqHfhY51ccZ9P19Kix3RnVT2QkSZ6NDF2SU1X6/U7w7uLyheYfAeHOq1rj3dmvw yb00ryJ/aku6vacH3mxMwh32s5jY4EWJILAH8s+uXovPzPeKJiwctRcHJCbfIY1LH+t1aZEGLBRA7 2kGnicvUHR7f553F4id0dgTLHH1zVmFE3prBaS9J8M3CxT5omwLe49Bu/us8gJP/SHpxbcNgnHDHL Elr25tpw5ou6roBIVMEQBZ+bFhJv/BHByROPDlsaNas0aY/ibANwAX7+iWFZW2Y+9TipKH8bSg6G0 Ox4TWHslQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kp5CJ-0006mL-HE; Tue, 15 Dec 2020 07:56:39 +0000 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 1kp5CE-0006lX-QQ for ath10k@lists.infradead.org; Tue, 15 Dec 2020 07:56:38 +0000 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1608018996; h=Content-Type: MIME-Version: Message-ID: In-Reply-To: Date: References: Subject: Cc: To: From: Sender; bh=w/DmYDE2LJLOcCmATu8luhG4VxtIYbdFGkom5uX02wM=; b=emyg0x2/aKtSLue1Lhi9KdBK0McigAQFH9g9yqBCmtIH5HYgwq5gvmEr98drS1rS4ov62JcZ LbLeM/cgR3zJPiAdbdqNTPsZOudjVVZa0zPmIvfi9wO+O+P6WhwQ8OCYMg9X9tkYqqdacewL qiVNZdXp4u0qTqSlCXd9YnP7mUw= X-Mailgun-Sending-Ip: 198.61.254.31 X-Mailgun-Sid: WyJiZDQ3OSIsICJhdGgxMGtAbGlzdHMuaW5mcmFkZWFkLm9yZyIsICJiZTllNGEiXQ== Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n06.prod.us-east-1.postgun.com with SMTP id 5fd86c299021521a4137593f (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Tue, 15 Dec 2020 07:56:25 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 3E2ECC433C6; Tue, 15 Dec 2020 07:56:24 +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 309ABC433CA; Tue, 15 Dec 2020 07:56:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 309ABC433CA 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: Ben Greear 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> <87r1nzbadn.fsf@codeaurora.org> <8a97f5ba-8eba-d61b-4c92-bdfd08d388ee@candelatech.com> Date: Tue, 15 Dec 2020 09:56:20 +0200 In-Reply-To: <8a97f5ba-8eba-d61b-4c92-bdfd08d388ee@candelatech.com> (Ben Greear's message of "Wed, 9 Dec 2020 07:00:52 -0800") Message-ID: <87y2hz1p0b.fsf@codeaurora.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201215_025636_321553_D2AAF997 X-CRM114-Status: GOOD ( 17.82 ) X-BeenThere: ath10k@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-wireless@vger.kernel.org, ath10k@lists.infradead.org, Wen Gong Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "ath10k" Errors-To: ath10k-bounces+ath10k=archiver.kernel.org@lists.infradead.org Ben Greear writes: > 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? Good point, there is a race. I now fixed the patch in the pending and documented that core_mutex needs to be held when changing the NAPI state: https://git.kernel.org/pub/scm/linux/kernel/git/kvalo/ath.git/commit/?h=pending&id=2fe769592ef6d4ae14260989dcbdbde4bff01cb6 -- 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 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=-8.8 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 BEAF2C4361B for ; Tue, 15 Dec 2020 07:57:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7851622273 for ; Tue, 15 Dec 2020 07:57:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726627AbgLOH5V (ORCPT ); Tue, 15 Dec 2020 02:57:21 -0500 Received: from m43-15.mailgun.net ([69.72.43.15]:18877 "EHLO m43-15.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726249AbgLOH5V (ORCPT ); Tue, 15 Dec 2020 02:57:21 -0500 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1608019018; h=Content-Type: MIME-Version: Message-ID: In-Reply-To: Date: References: Subject: Cc: To: From: Sender; bh=w/DmYDE2LJLOcCmATu8luhG4VxtIYbdFGkom5uX02wM=; b=PEXVX7ItzwKmFBsx372r699MAhWE0fSUgTNzGkUyacevufrLwYVheJyQU8E9TVAbezWZACs/ Gfeq51lR6TNEpg3jZmGJEF+whiAY0iE9Deg3r+yBxdn1XauEPXWOpXnaPFIPriEVFwIF8B7j vAhpnyM98ptlLvYSa+qj5AjphwE= 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 5fd86c2a5723412e5431ef8e (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Tue, 15 Dec 2020 07:56:26 GMT Sender: kvalo=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 4C215C433CA; Tue, 15 Dec 2020 07:56:24 +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 309ABC433CA; Tue, 15 Dec 2020 07:56:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 309ABC433CA 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: Ben Greear Cc: Wen Gong , 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> <87r1nzbadn.fsf@codeaurora.org> <8a97f5ba-8eba-d61b-4c92-bdfd08d388ee@candelatech.com> Date: Tue, 15 Dec 2020 09:56:20 +0200 In-Reply-To: <8a97f5ba-8eba-d61b-4c92-bdfd08d388ee@candelatech.com> (Ben Greear's message of "Wed, 9 Dec 2020 07:00:52 -0800") Message-ID: <87y2hz1p0b.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 Ben Greear writes: > 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? Good point, there is a race. I now fixed the patch in the pending and documented that core_mutex needs to be held when changing the NAPI state: https://git.kernel.org/pub/scm/linux/kernel/git/kvalo/ath.git/commit/?h=pending&id=2fe769592ef6d4ae14260989dcbdbde4bff01cb6 -- https://patchwork.kernel.org/project/linux-wireless/list/ https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches