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=-18.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 D0E83C433DB for ; Tue, 2 Feb 2021 18:56:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 98AAB64E75 for ; Tue, 2 Feb 2021 18:56:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239087AbhBBSzo (ORCPT ); Tue, 2 Feb 2021 13:55:44 -0500 Received: from mail.kernel.org ([198.145.29.99]:46494 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233689AbhBBOCP (ORCPT ); Tue, 2 Feb 2021 09:02:15 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id C029065003; Tue, 2 Feb 2021 13:47:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1612273661; bh=NZLzufu96XX1xC0tldQ0nYLHC18eDCiMdXazW5FzoYw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=plMcAjdqQfXNq0MbtXVJ/cBzi/t+xmbQrECRTbVc4ML2gwiEEIalgBgM5wqf/HNr8 sJHb8J0CYq9lHz4UHLiUydxzvaZ/QcGXY+dF1t0RqjZ0o9hjvnlAHQvw6ST2Qkr7xc Zk2WC2xxJ90W8Um6u/RanNHoDTSqwVsbUvw+4UFk= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Johannes Berg , Luca Coelho , Kalle Valo , Sasha Levin Subject: [PATCH 5.4 44/61] iwlwifi: pcie: reschedule in long-running memory reads Date: Tue, 2 Feb 2021 14:38:22 +0100 Message-Id: <20210202132948.334733085@linuxfoundation.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210202132946.480479453@linuxfoundation.org> References: <20210202132946.480479453@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Johannes Berg [ Upstream commit 3d372c4edfd4dffb7dea71c6b096fb414782b776 ] If we spin for a long time in memory reads that (for some reason in hardware) take a long time, then we'll eventually get messages such as watchdog: BUG: soft lockup - CPU#2 stuck for 24s! [kworker/2:2:272] This is because the reading really does take a very long time, and we don't schedule, so we're hogging the CPU with this task, at least if CONFIG_PREEMPT is not set, e.g. with CONFIG_PREEMPT_VOLUNTARY=y. Previously I misinterpreted the situation and thought that this was only going to happen if we had interrupts disabled, and then fixed this (which is good anyway, however), but that didn't always help; looking at it again now I realized that the spin unlock will only reschedule if CONFIG_PREEMPT is used. In order to avoid this issue, change the code to cond_resched() if we've been spinning for too long here. Signed-off-by: Johannes Berg Fixes: 04516706bb99 ("iwlwifi: pcie: limit memory read spin time") Signed-off-by: Luca Coelho Signed-off-by: Kalle Valo Link: https://lore.kernel.org/r/iwlwifi.20210115130253.217a9d6a6a12.If964cb582ab0aaa94e81c4ff3b279eaafda0fd3f@changeid Signed-off-by: Sasha Levin --- drivers/net/wireless/intel/iwlwifi/pcie/trans.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/trans.c b/drivers/net/wireless/intel/iwlwifi/pcie/trans.c index d2ed9e0239cb9..0581f082301e0 100644 --- a/drivers/net/wireless/intel/iwlwifi/pcie/trans.c +++ b/drivers/net/wireless/intel/iwlwifi/pcie/trans.c @@ -2184,6 +2184,7 @@ static int iwl_trans_pcie_read_mem(struct iwl_trans *trans, u32 addr, while (offs < dwords) { /* limit the time we spin here under lock to 1/2s */ unsigned long end = jiffies + HZ / 2; + bool resched = false; if (iwl_trans_grab_nic_access(trans, &flags)) { iwl_write32(trans, HBUS_TARG_MEM_RADDR, @@ -2194,10 +2195,15 @@ static int iwl_trans_pcie_read_mem(struct iwl_trans *trans, u32 addr, HBUS_TARG_MEM_RDAT); offs++; - if (time_after(jiffies, end)) + if (time_after(jiffies, end)) { + resched = true; break; + } } iwl_trans_release_nic_access(trans, &flags); + + if (resched) + cond_resched(); } else { return -EBUSY; } -- 2.27.0