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