From: Julian Wiedmann <jwi@linux.ibm.com>
Date: Thu, 7 Jan 2021 18:24:40 +0100
Subject: s390/qeth: fix deadlock during recovery
Git-commit: 0b9902c1fcc59ba75268386c0420a554f8844168
Patch-mainline: v5.11-rc3
References: git-fixes
When qeth_dev_layer2_store() - holding the discipline_mutex - waits
inside qeth_l*_remove_device() for a qeth_do_reset() thread to complete,
we can hit a deadlock if qeth_do_reset() concurrently calls
qeth_set_online() and thus tries to aquire the discipline_mutex.
Move the discipline_mutex locking outside of qeth_set_online() and
qeth_set_offline(), and turn the discipline into a parameter so that
callers understand the dependency.
To fix the deadlock, we can now relax the locking:
As already established, qeth_l*_remove_device() waits for
qeth_do_reset() to complete. So qeth_do_reset() itself is under no risk
of having card->discipline ripped out while it's running, and thus
doesn't need to take the discipline_mutex.
Fixes: 9dc48ccc68b9 ("qeth: serialize sysfs-triggered device configurations")
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Reviewed-by: Alexandra Winter <wintera@linux.ibm.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ ptesarik: Context heavily adapted, because SLE15-SP2 does not contain
upstream commit f2bcf9dd3ecf7c9340025fc0736416e1203b5e35.
The suspend/resume routines also had to be adapted. ]
Signed-off-by: Petr Tesarik <ptesarik@suse.com>
---
drivers/s390/net/qeth_core.h | 3 +-
drivers/s390/net/qeth_core_main.c | 43 +++++++++++++++++++++++++-------------
drivers/s390/net/qeth_l2_main.c | 7 ++++--
drivers/s390/net/qeth_l3_main.c | 7 ++++--
4 files changed, 41 insertions(+), 19 deletions(-)
--- a/drivers/s390/net/qeth_core.h
+++ b/drivers/s390/net/qeth_core.h
@@ -1039,7 +1039,8 @@ void qeth_set_allowed_threads(struct qet
int qeth_threads_running(struct qeth_card *, unsigned long);
int qeth_core_hardsetup_card(struct qeth_card *card, bool *carrier_ok);
int qeth_stop_channel(struct qeth_channel *channel);
-int qeth_set_offline(struct qeth_card *card, bool resetting);
+int qeth_set_offline(struct qeth_card *card, const struct qeth_discipline *disc,
+ bool resetting);
void qeth_print_status_message(struct qeth_card *);
int qeth_send_ipa_cmd(struct qeth_card *, struct qeth_cmd_buffer *,
--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -5117,27 +5117,26 @@ out:
}
EXPORT_SYMBOL_GPL(qeth_core_hardsetup_card);
-static int qeth_set_online(struct qeth_card *card)
+static int qeth_set_online(struct qeth_card *card,
+ const struct qeth_discipline *disc)
{
int rc;
- mutex_lock(&card->discipline_mutex);
mutex_lock(&card->conf_mutex);
QETH_CARD_TEXT(card, 2, "setonlin");
- rc = card->discipline->set_online(card);
+ rc = disc->set_online(card);
mutex_unlock(&card->conf_mutex);
- mutex_unlock(&card->discipline_mutex);
return rc;
}
-int qeth_set_offline(struct qeth_card *card, bool resetting)
+int qeth_set_offline(struct qeth_card *card, const struct qeth_discipline *disc,
+ bool resetting)
{
int rc, rc2, rc3;
- mutex_lock(&card->discipline_mutex);
mutex_lock(&card->conf_mutex);
QETH_CARD_TEXT(card, 3, "setoffl");
@@ -5153,7 +5152,7 @@ int qeth_set_offline(struct qeth_card *c
netif_carrier_off(card->dev);
rtnl_unlock();
- card->discipline->set_offline(card);
+ disc->set_offline(card);
rc = qeth_stop_channel(&card->data);
rc2 = qeth_stop_channel(&card->write);
@@ -5168,16 +5167,19 @@ int qeth_set_offline(struct qeth_card *c
kobject_uevent(&card->gdev->dev.kobj, KOBJ_CHANGE);
mutex_unlock(&card->conf_mutex);
- mutex_unlock(&card->discipline_mutex);
return 0;
}
EXPORT_SYMBOL_GPL(qeth_set_offline);
static int qeth_do_reset(void *data)
{
+ const struct qeth_discipline *disc;
struct qeth_card *card = data;
int rc;
+ /* Lock-free, other users will block until we are done. */
+ disc = card->discipline;
+
QETH_CARD_TEXT(card, 2, "recover1");
if (!qeth_do_run_thread(card, QETH_RECOVER_THREAD))
return 0;
@@ -5185,8 +5187,8 @@ static int qeth_do_reset(void *data)
dev_warn(&card->gdev->dev,
"A recovery process has been started for the device\n");
- qeth_set_offline(card, true);
- rc = qeth_set_online(card);
+ qeth_set_offline(card, disc, true);
+ rc = qeth_set_online(card, disc);
if (!rc) {
dev_info(&card->gdev->dev,
"Device successfully recovered!\n");
@@ -6009,7 +6011,10 @@ static int qeth_core_set_online(struct c
}
}
- rc = qeth_set_online(card);
+ mutex_lock(&card->discipline_mutex);
+ rc = qeth_set_online(card, card->discipline);
+ mutex_unlock(&card->discipline_mutex);
+
err:
return rc;
}
@@ -6017,8 +6022,13 @@ err:
static int qeth_core_set_offline(struct ccwgroup_device *gdev)
{
struct qeth_card *card = dev_get_drvdata(&gdev->dev);
+ int rc;
- return qeth_set_offline(card, false);
+ mutex_lock(&card->discipline_mutex);
+ rc = qeth_set_offline(card, card->discipline, false);
+ mutex_unlock(&card->discipline_mutex);
+
+ return rc;
}
static void qeth_core_shutdown(struct ccwgroup_device *gdev)
@@ -6041,7 +6051,10 @@ static int qeth_suspend(struct ccwgroup_
if (gdev->state == CCWGROUP_OFFLINE)
return 0;
- qeth_set_offline(card, false);
+ mutex_lock(&card->discipline_mutex);
+ qeth_set_offline(card, card->discipline, false);
+ mutex_unlock(&card->discipline_mutex);
+
return 0;
}
@@ -6050,7 +6063,9 @@ static int qeth_resume(struct ccwgroup_d
struct qeth_card *card = dev_get_drvdata(&gdev->dev);
int rc;
- rc = qeth_set_online(card);
+ mutex_lock(&card->discipline_mutex);
+ rc = qeth_set_online(card, card->discipline);
+ mutex_unlock(&card->discipline_mutex);
qeth_set_allowed_threads(card, 0xffffffff, 0);
if (rc)
--- a/drivers/s390/net/qeth_l2_main.c
+++ b/drivers/s390/net/qeth_l2_main.c
@@ -646,8 +646,11 @@ static void qeth_l2_remove_device(struct
qeth_set_allowed_threads(card, 0, 1);
wait_event(card->wait_q, qeth_threads_running(card, 0xffffffff) == 0);
- if (cgdev->state == CCWGROUP_ONLINE)
- qeth_set_offline(card, false);
+ if (cgdev->state == CCWGROUP_ONLINE) {
+ mutex_lock(&card->discipline_mutex);
+ qeth_set_offline(card, card->discipline, false);
+ mutex_unlock(&card->discipline_mutex);
+ }
cancel_work_sync(&card->close_dev_work);
if (qeth_netdev_is_registered(card->dev))
--- a/drivers/s390/net/qeth_l3_main.c
+++ b/drivers/s390/net/qeth_l3_main.c
@@ -2164,8 +2164,11 @@ static void qeth_l3_remove_device(struct
qeth_set_allowed_threads(card, 0, 1);
wait_event(card->wait_q, qeth_threads_running(card, 0xffffffff) == 0);
- if (cgdev->state == CCWGROUP_ONLINE)
- qeth_set_offline(card, false);
+ if (cgdev->state == CCWGROUP_ONLINE) {
+ mutex_lock(&card->discipline_mutex);
+ qeth_set_offline(card, card->discipline, false);
+ mutex_unlock(&card->discipline_mutex);
+ }
cancel_work_sync(&card->close_dev_work);
if (qeth_netdev_is_registered(card->dev))