[PATCH 5.14 017/172] s390/qeth: fix deadlock during failing recovery

Greg Kroah-Hartman
2021-10-04T13:28:19Z

From: Alexandra Winter <wintera@linux.ibm.com>

[ Upstream commit d2b59bd4b06d84a4eadb520b0f71c62fe8ec0a62 ]

Commit 0b9902c1fcc5 ("s390/qeth: fix deadlock during recovery") removed
taking discipline_mutex inside qeth_do_reset(), fixing potential
deadlocks. An error path was missed though, that still takes
discipline_mutex and thus has the original deadlock potential.

Intermittent deadlocks were seen when a qeth channel path is configured
offline, causing a race between qeth_do_reset and ccwgroup_remove.
Call qeth_set_offline() directly in the qeth_do_reset() error case and
then a new variant of ccwgroup_set_offline(), without taking
discipline_mutex.

Fixes: b41b554c1ee7 ("s390/qeth: fix locking for discipline setup / removal")
Signed-off-by: Alexandra Winter <wintera@linux.ibm.com>
Reviewed-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/s390/include/asm/ccwgroup.h | 2 +-
drivers/s390/cio/ccwgroup.c | 10 ++++++++--
drivers/s390/net/qeth_core_main.c | 3 ++-
3 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/arch/s390/include/asm/ccwgroup.h b/arch/s390/include/asm/ccwgroup.h
index 20f169b6db4e..d97301d9d0b8 100644
--- a/arch/s390/include/asm/ccwgroup.h
+++ b/arch/s390/include/asm/ccwgroup.h
@@ -57,7 +57,7 @@ struct ccwgroup_device *get_ccwgroupdev_by_busid(struct ccwgroup_driver *gdrv,
char *bus_id);

extern int ccwgroup_set_online(struct ccwgroup_device *gdev);
-extern int ccwgroup_set_offline(struct ccwgroup_device *gdev);
+int ccwgroup_set_offline(struct ccwgroup_device *gdev, bool call_gdrv);

extern int ccwgroup_probe_ccwdev(struct ccw_device *cdev);
extern void ccwgroup_remove_ccwdev(struct ccw_device *cdev);
diff --git a/drivers/s390/cio/ccwgroup.c b/drivers/s390/cio/ccwgroup.c
index 9748165e08e9..f19f02e75115 100644
--- a/drivers/s390/cio/ccwgroup.c
+++ b/drivers/s390/cio/ccwgroup.c
@@ -77,12 +77,13 @@ EXPORT_SYMBOL(ccwgroup_set_online);
/**
* ccwgroup_set_offline() - disable a ccwgroup device
* @gdev: target ccwgroup device
+ * @call_gdrv: Call the registered gdrv set_offline function
*
* This function attempts to put the ccwgroup device into the offline state.
* Returns:
* %0 on success and a negative error value on failure.
*/
-int ccwgroup_set_offline(struct ccwgroup_device *gdev)
+int ccwgroup_set_offline(struct ccwgroup_device *gdev, bool call_gdrv)
{
struct ccwgroup_driver *gdrv = to_ccwgroupdrv(gdev->dev.driver);
int ret = -EINVAL;
@@ -91,11 +92,16 @@ int ccwgroup_set_offline(struct ccwgroup_device *gdev)
return -EAGAIN;
if (gdev->state == CCWGROUP_OFFLINE)
goto out;
+ if (!call_gdrv) {
+ ret = 0;
+ goto offline;
+ }
if (gdrv->set_offline)
ret = gdrv->set_offline(gdev);
if (ret)
goto out;

+offline:
gdev->state = CCWGROUP_OFFLINE;
out:
atomic_set(&gdev->onoff, 0);
@@ -124,7 +130,7 @@ static ssize_t ccwgroup_online_store(struct device *dev,
if (value == 1)
ret = ccwgroup_set_online(gdev);
else if (value == 0)
- ret = ccwgroup_set_offline(gdev);
+ ret = ccwgroup_set_offline(gdev, true);
else
ret = -EINVAL;
out:
diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c
index dba3b345218f..f5bad10f3f44 100644
--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -5548,7 +5548,8 @@ static int qeth_do_reset(void *data)
dev_info(&card->gdev->dev,
"Device successfully recovered!\n");
} else {
- ccwgroup_set_offline(card->gdev);
+ qeth_set_offline(card, disc, true);
+ ccwgroup_set_offline(card->gdev, false);
dev_warn(&card->gdev->dev,
"The qeth device driver failed to recover an error on the device\n");
}
--
2.33.0