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=-14.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,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 6B631C433E1 for ; Mon, 24 Aug 2020 17:18:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4944D20738 for ; Mon, 24 Aug 2020 17:18:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598289493; bh=r9HBhZi5uRfTCPjOUZlAFzjcdKyoVIqdk98dp7qcDAI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=EQAntaBRVZj0iNlH95IxAL9l++MLFxHiTXlOXpq3O09k/L5UgARGgEgO2iPaSi2zf 1bXUF8BPr+QIM57GjVD3cIc70E9le7Kr5dC0C4C4FxcGJRYuoTZEl6pjyRj2JKeOzo nmUXnkoWl+cMnusnbIwGNtb8LYQF08a9gdLzsG9U= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728156AbgHXRR6 (ORCPT ); Mon, 24 Aug 2020 13:17:58 -0400 Received: from mail.kernel.org ([198.145.29.99]:40164 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728298AbgHXQgj (ORCPT ); Mon, 24 Aug 2020 12:36:39 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A8D9722D04; Mon, 24 Aug 2020 16:36:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598286961; bh=r9HBhZi5uRfTCPjOUZlAFzjcdKyoVIqdk98dp7qcDAI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hgBcG/7KD9bulRRhKzF5njETlnlqZvZr8oORAZMQ3eJAQu/lmXi54JMcnhvKFLdBO VwqptH+aebpv8Xrq5NPfFNqyJnTfzOSBnHHO+vEmhsO2lawgX/Ic0kUoT/9+J/uYQl 1lZjSNF0B8uJj+9LYkw6rSmEakfQQiWQjCVDXzf0= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Douglas Gilbert , John Garry , Lee Duncan , "Martin K . Petersen" , Sasha Levin , linux-scsi@vger.kernel.org Subject: [PATCH AUTOSEL 5.8 42/63] scsi: scsi_debug: Fix scp is NULL errors Date: Mon, 24 Aug 2020 12:34:42 -0400 Message-Id: <20200824163504.605538-42-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200824163504.605538-1-sashal@kernel.org> References: <20200824163504.605538-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Douglas Gilbert [ Upstream commit 223f91b48079227f914657f07d2d686f7b60aa26 ] John Garry reported 'sdebug_q_cmd_complete: scp is NULL' failures that were mainly seen on aarch64 machines (e.g. RPi 4 with four A72 CPUs). The problem was tracked down to a missing critical section on a "short circuit" path. Namely, the time to process the current command so far has already exceeded the requested command duration (i.e. the number of nanoseconds in the ndelay parameter). The random=1 parameter setting was pivotal in finding this error. The failure scenario involved first taking that "short circuit" path (due to a very short command duration) and then taking the more likely hrtimer_start() path (due to a longer command duration). With random=1 each command's duration is taken from the uniformly distributed [0..ndelay) interval. The fio utility also helped by reliably generating the error scenario at about once per minute on a RPi 4 (64 bit OS). Link: https://lore.kernel.org/r/20200813155738.109298-1-dgilbert@interlog.com Reported-by: John Garry Reviewed-by: Lee Duncan Signed-off-by: Douglas Gilbert Signed-off-by: Martin K. Petersen Signed-off-by: Sasha Levin --- drivers/scsi/scsi_debug.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c index b0d93bf79978f..25faad7f8e617 100644 --- a/drivers/scsi/scsi_debug.c +++ b/drivers/scsi/scsi_debug.c @@ -5486,9 +5486,11 @@ static int schedule_resp(struct scsi_cmnd *cmnd, struct sdebug_dev_info *devip, u64 d = ktime_get_boottime_ns() - ns_from_boot; if (kt <= d) { /* elapsed duration >= kt */ + spin_lock_irqsave(&sqp->qc_lock, iflags); sqcp->a_cmnd = NULL; atomic_dec(&devip->num_in_q); clear_bit(k, sqp->in_use_bm); + spin_unlock_irqrestore(&sqp->qc_lock, iflags); if (new_sd_dp) kfree(sd_dp); /* call scsi_done() from this thread */ -- 2.25.1