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Mon, 8 Mar 2021 22:54:27 +0000 (GMT) Received: from v0005c16.aus.stglabs.ibm.com (unknown [9.211.41.147]) by b03ledav006.gho.boulder.ibm.com (Postfix) with ESMTP; Mon, 8 Mar 2021 22:54:27 +0000 (GMT) From: Eddie James To: openbmc@lists.ozlabs.org Subject: [PATCH linux dev-5.10 27/35] net/ncsi: Avoid channel_monitor hrtimer deadlock Date: Mon, 8 Mar 2021 16:54:11 -0600 Message-Id: <20210308225419.46530-28-eajames@linux.ibm.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20210308225419.46530-1-eajames@linux.ibm.com> References: <20210308225419.46530-1-eajames@linux.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369, 18.0.761 definitions=2021-03-08_20:2021-03-08, 2021-03-08 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 clxscore=1015 impostorscore=0 mlxlogscore=999 malwarescore=0 mlxscore=0 spamscore=0 lowpriorityscore=0 bulkscore=0 phishscore=0 priorityscore=1501 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2103080118 X-BeenThere: openbmc@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Development list for OpenBMC List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: openbmc-bounces+openbmc=archiver.kernel.org@lists.ozlabs.org Sender: "openbmc" From: Milton Miller Calling ncsi_stop_channel_monitor from channel_monitor is a guaranteed deadlock on SMP because stop calls del_timer_sync on the timer that inoked channel_monitor as its timer function. Recognise the inherent race of marking the monitor disabled before deleting the timer by just returning if enable was cleared. After a timeout (the default case -- reset to START when response recieved) just mark the monitor.enabled false. If the channel has an entrie on the channel_queue list, or if the the state is not ACTIVE or INACTIVE, then warn and mark the timer stopped and don't restart, as the locking is broken somehow. Fixes: 0795fb2021f0 ("net/ncsi: Stop monitor if channel times out or is inactive") Signed-off-by: Milton Miller --- net/ncsi/ncsi-manage.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/net/ncsi/ncsi-manage.c b/net/ncsi/ncsi-manage.c index a9cb355324d1..5a2beaf874c7 100644 --- a/net/ncsi/ncsi-manage.c +++ b/net/ncsi/ncsi-manage.c @@ -105,13 +105,20 @@ static void ncsi_channel_monitor(struct timer_list *t) monitor_state = nc->monitor.state; spin_unlock_irqrestore(&nc->lock, flags); - if (!enabled || chained) { - ncsi_stop_channel_monitor(nc); - return; + if (!enabled) + return; /* expected race disabling timer */ + if (WARN_ON_ONCE(chained)) { + goto bad_state; } if (state != NCSI_CHANNEL_INACTIVE && state != NCSI_CHANNEL_ACTIVE) { - ncsi_stop_channel_monitor(nc); +bad_state: + netdev_warn(ndp->ndev.dev, + "Bad NCSI monitor state channel %d 0x%x %s queue\n", + nc->id, state, chained ? "on" : "off"); + spin_lock_irqsave(&nc->lock, flags); + nc->monitor.enabled = false; + spin_unlock_irqrestore(&nc->lock, flags); return; } @@ -136,10 +143,9 @@ static void ncsi_channel_monitor(struct timer_list *t) ncsi_report_link(ndp, true); ndp->flags |= NCSI_DEV_RESHUFFLE; - ncsi_stop_channel_monitor(nc); - ncm = &nc->modes[NCSI_MODE_LINK]; spin_lock_irqsave(&nc->lock, flags); + nc->monitor.enabled = false; nc->state = NCSI_CHANNEL_INVISIBLE; ncm->data[2] &= ~0x1; spin_unlock_irqrestore(&nc->lock, flags); -- 2.27.0