From patchwork Tue Feb 2 13:38:49 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: 375226 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 CC1EAC433E0 for ; Tue, 2 Feb 2021 17:51:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A460B64F93 for ; Tue, 2 Feb 2021 17:51:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237758AbhBBRvV (ORCPT ); Tue, 2 Feb 2021 12:51:21 -0500 Received: from mail.kernel.org ([198.145.29.99]:48062 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233754AbhBBOJv (ORCPT ); Tue, 2 Feb 2021 09:09:51 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 3444164F99; Tue, 2 Feb 2021 13:50:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1612273858; bh=2ZQdflJ0IRcFyn4Mg7yQRUPkfdekW4o3Inms5uQK7QY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DFdCzzslt4x6fdcXeL1S30qzRGRGPjwBVGSAS0+ol7H/DZ7pOB34Mq8R2K7v5apSn xV/vOcmvFJpUSXBcko91drEQd4/07Hkx0/CrtwZy7m0g9kT6xO3F4k3GHEwRbqx8aR xEE9S5uKLLBq6tYlkqO9CMQNv0WPMH3F0V2LzwpY= 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 4.9 26/32] iwlwifi: pcie: reschedule in long-running memory reads Date: Tue, 2 Feb 2021 14:38:49 +0100 Message-Id: <20210202132943.060104477@linuxfoundation.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210202132942.035179752@linuxfoundation.org> References: <20210202132942.035179752@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 ed90f46626e7d..71edbf7a42ed4 100644 --- a/drivers/net/wireless/intel/iwlwifi/pcie/trans.c +++ b/drivers/net/wireless/intel/iwlwifi/pcie/trans.c @@ -1910,6 +1910,7 @@ 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, @@ -1920,10 +1921,15 @@ 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; }