linux-kernel - [PATCH v3 7/7] libsas: release disco mutex during waiting in sas_ex_discover_end

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Date:   Mon, 10 Jul 2017 15:06:09 +0800
From:   Yijing Wang <wangyijing@...wei.com>
To:     <jejb@...ux.vnet.ibm.com>, <martin.petersen@...cle.com>
CC:     <chenqilin2@...wei.com>, <hare@...e.com>,
        <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <chenxiang66@...ilicon.com>, <huangdaode@...ilicon.com>,
        <wangkefeng.wang@...wei.com>, <zhaohongjiang@...wei.com>,
        <dingtianhong@...wei.com>, <guohanjun@...wei.com>,
        <yanaijie@...wei.com>, <hch@....de>, <dan.j.williams@...el.com>,
        <emilne@...hat.com>, <thenzl@...hat.com>, <wefu@...hat.com>,
        <charles.chenxin@...wei.com>, <chenweilong@...wei.com>,
        <john.garry@...wei.com>, Yijing Wang <wangyijing@...wei.com>,
        "Johannes Thumshirn" <jthumshirn@...e.de>
Subject: [PATCH v3 7/7] libsas: release disco mutex during waiting in sas_ex_discover_end_dev

Disco mutex was introudced to prevent domain rediscovery competing
with ata error handling(87c8331). If we have already hold the lock
in sas_revalidate_domain and sync executing probe, deadlock caused,
because, sas_probe_sata() also need hold disco_mutex. Since disco mutex
use to prevent revalidata domain happen during ata error handler,
it should be safe to release disco mutex when sync probe, because
no new revalidate domain event would be process until the sync return,
and the current sas revalidate domain finish.

Signed-off-by: Yijing Wang <wangyijing@...wei.com>
CC: John Garry <john.garry@...wei.com>
CC: Johannes Thumshirn <jthumshirn@...e.de>
CC: Ewan Milne <emilne@...hat.com>
CC: Christoph Hellwig <hch@....de>
CC: Tomas Henzl <thenzl@...hat.com>
CC: Dan Williams <dan.j.williams@...el.com>
---
 drivers/scsi/libsas/sas_expander.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
index 9d26c28..077024e 100644
--- a/drivers/scsi/libsas/sas_expander.c
+++ b/drivers/scsi/libsas/sas_expander.c
@@ -776,6 +776,7 @@ static struct domain_device *sas_ex_discover_end_dev(
 	struct ex_phy *phy = &parent_ex->ex_phy[phy_id];
 	struct domain_device *child = NULL;
 	struct sas_rphy *rphy;
+	bool prev_lock;
 	int res;
 
 	if (phy->attached_sata_host || phy->attached_sata_ps)
@@ -803,6 +804,7 @@ static struct domain_device *sas_ex_discover_end_dev(
 	sas_ex_get_linkrate(parent, child, phy);
 	sas_device_set_phy(child, phy->port);
 
+	prev_lock = mutex_is_locked(&child->port->ha->disco_mutex);
 #ifdef CONFIG_SCSI_SAS_ATA
 	if ((phy->attached_tproto & SAS_PROTOCOL_STP) || phy->attached_sata_dev) {
 		res = sas_get_ata_info(child, phy);
@@ -832,7 +834,11 @@ static struct domain_device *sas_ex_discover_end_dev(
 				    SAS_ADDR(parent->sas_addr), phy_id, res);
 			goto out_list_del;
 		}
+		if (prev_lock)
+			mutex_unlock(&child->port->ha->disco_mutex);
 		sas_disc_wait_completion(child->port, DISCE_PROBE);
+		if (prev_lock)
+			mutex_lock(&child->port->ha->disco_mutex);
 
 	} else
 #endif
@@ -861,7 +867,11 @@ static struct domain_device *sas_ex_discover_end_dev(
 				    SAS_ADDR(parent->sas_addr), phy_id, res);
 			goto out_list_del;
 		}
+		if (prev_lock)
+			mutex_unlock(&child->port->ha->disco_mutex);
 		sas_disc_wait_completion(child->port, DISCE_PROBE);
+		if (prev_lock)
+			mutex_lock(&child->port->ha->disco_mutex);
 	} else {
 		SAS_DPRINTK("target proto 0x%x at %016llx:0x%x not handled\n",
 			    phy->attached_tproto, SAS_ADDR(parent->sas_addr),
-- 
2.5.0