From patchwork Tue Feb 2 13:37:48 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 375170 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=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, 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 3CAFAC433E6 for ; Tue, 2 Feb 2021 19:48:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 115DF64E56 for ; Tue, 2 Feb 2021 19:48:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240038AbhBBTr2 (ORCPT ); Tue, 2 Feb 2021 14:47:28 -0500 Received: from mail.kernel.org ([198.145.29.99]:41654 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233249AbhBBNwv (ORCPT ); Tue, 2 Feb 2021 08:52:51 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 6232164FC6; Tue, 2 Feb 2021 13:43:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1612273436; bh=AevGPiwEm7doZPMOnBMl1STziuyk8McrepJEazOcYHY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=L5W8nqnIVptXmdmP8PXcnv4R04Yl0eoaGWI+O1scxL1u9dbf3VmhFDIEFFLsxZjL+ iazKTI3+M2q4zg42B7Q6SPaQ9HfoQSHISbbvR/BHGCkXNkWRbHib3B7tIUfKU3pP3n pMT7GxLzvL6UFWLfC6znQNUa16Ne168KvsolF5/I= 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 5.10 105/142] iwlwifi: pcie: reschedule in long-running memory reads Date: Tue, 2 Feb 2021 14:37:48 +0100 Message-Id: <20210202133002.041646325@linuxfoundation.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210202132957.692094111@linuxfoundation.org> References: <20210202132957.692094111@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 c7161f121c0c2..1a222469b5b4e 100644 --- a/drivers/net/wireless/intel/iwlwifi/pcie/trans.c +++ b/drivers/net/wireless/intel/iwlwifi/pcie/trans.c @@ -2162,6 +2162,7 @@ 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, @@ -2172,10 +2173,15 @@ 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; }