From patchwork Tue Feb 2 13:39:10 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 376063 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=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 09A28C433E6 for ; Tue, 2 Feb 2021 16:19:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BB5F964F71 for ; Tue, 2 Feb 2021 16:19:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234851AbhBBQTI (ORCPT ); Tue, 2 Feb 2021 11:19:08 -0500 Received: from mail.kernel.org ([198.145.29.99]:51350 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230224AbhBBOQC (ORCPT ); Tue, 2 Feb 2021 09:16:02 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id E3D5D6505B; Tue, 2 Feb 2021 13:53:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1612274034; bh=v1N9oTk/0UTcpSNW0o3l3MhznrA2CRHQ7GsADeaDB2I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=rK5prnbAGK02eWR10WLrUk2w5rEbwCjjMxsLoR0tah8c1nLlkSXi4W7d6XRKu2FRB /iSmt/YNNLdVkQBFvlam1c3cKJP0PlCZZkp+i8018uukVJV4jFKKnEGBUyWSeadIc4 xxX9TnRIJ9KdtkRc2UK/uJcngAMZjbvkVZs6vROc= 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 4.19 27/37] iwlwifi: pcie: reschedule in long-running memory reads Date: Tue, 2 Feb 2021 14:39:10 +0100 Message-Id: <20210202132944.059440795@linuxfoundation.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210202132942.915040339@linuxfoundation.org> References: <20210202132942.915040339@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@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 fe772b716a8df..fcda33482887b 100644 --- a/drivers/net/wireless/intel/iwlwifi/pcie/trans.c +++ b/drivers/net/wireless/intel/iwlwifi/pcie/trans.c @@ -2127,6 +2127,7 @@ 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, @@ -2137,10 +2138,15 @@ 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; }