The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 0b9902c1fcc59ba75268386c0420a554f8844168 Mon Sep 17 00:00:00 2001
From: Julian Wiedmann jwi@linux.ibm.com Date: Thu, 7 Jan 2021 18:24:40 +0100 Subject: [PATCH] s390/qeth: fix deadlock during recovery
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
diff --git a/drivers/s390/net/qeth_core.h b/drivers/s390/net/qeth_core.h index 6f5ddc3eab8c..28f637042d44 100644 --- a/drivers/s390/net/qeth_core.h +++ b/drivers/s390/net/qeth_core.h @@ -1079,7 +1079,8 @@ struct qeth_card *qeth_get_card_by_busid(char *bus_id); void qeth_set_allowed_threads(struct qeth_card *card, unsigned long threads, int clear_start_mask); int qeth_threads_running(struct qeth_card *, unsigned long); -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 qeth_send_ipa_cmd(struct qeth_card *, struct qeth_cmd_buffer *, int (*reply_cb) diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c index f4b60294a969..d45e223fc521 100644 --- a/drivers/s390/net/qeth_core_main.c +++ b/drivers/s390/net/qeth_core_main.c @@ -5507,12 +5507,12 @@ static int qeth_hardsetup_card(struct qeth_card *card, bool *carrier_ok) return rc; }
-static int qeth_set_online(struct qeth_card *card) +static int qeth_set_online(struct qeth_card *card, + const struct qeth_discipline *disc) { bool carrier_ok; int rc;
- mutex_lock(&card->discipline_mutex); mutex_lock(&card->conf_mutex); QETH_CARD_TEXT(card, 2, "setonlin");
@@ -5529,7 +5529,7 @@ static int qeth_set_online(struct qeth_card *card) /* no need for locking / error handling at this early stage: */ qeth_set_real_num_tx_queues(card, qeth_tx_actual_queues(card));
- rc = card->discipline->set_online(card, carrier_ok); + rc = disc->set_online(card, carrier_ok); if (rc) goto err_online;
@@ -5537,7 +5537,6 @@ static int qeth_set_online(struct qeth_card *card) kobject_uevent(&card->gdev->dev.kobj, KOBJ_CHANGE);
mutex_unlock(&card->conf_mutex); - mutex_unlock(&card->discipline_mutex); return 0;
err_online: @@ -5552,15 +5551,14 @@ static int qeth_set_online(struct qeth_card *card) qdio_free(CARD_DDEV(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");
@@ -5581,7 +5579,7 @@ int qeth_set_offline(struct qeth_card *card, bool resetting)
cancel_work_sync(&card->rx_mode_work);
- card->discipline->set_offline(card); + disc->set_offline(card);
qeth_qdio_clear_card(card, 0); qeth_drain_output_queues(card); @@ -5602,16 +5600,19 @@ int qeth_set_offline(struct qeth_card *card, bool resetting) 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; @@ -5619,8 +5620,8 @@ 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"); @@ -6647,7 +6648,10 @@ static int qeth_core_set_online(struct ccwgroup_device *gdev) } }
- 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; } @@ -6655,8 +6659,13 @@ static int qeth_core_set_online(struct ccwgroup_device *gdev) 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) diff --git a/drivers/s390/net/qeth_l2_main.c b/drivers/s390/net/qeth_l2_main.c index 4ed0fb0705a5..37279b1e29f6 100644 --- a/drivers/s390/net/qeth_l2_main.c +++ b/drivers/s390/net/qeth_l2_main.c @@ -2207,8 +2207,11 @@ static void qeth_l2_remove_device(struct ccwgroup_device *gdev) qeth_set_allowed_threads(card, 0, 1); wait_event(card->wait_q, qeth_threads_running(card, 0xffffffff) == 0);
- if (gdev->state == CCWGROUP_ONLINE) - qeth_set_offline(card, false); + if (gdev->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 (card->dev->reg_state == NETREG_REGISTERED) diff --git a/drivers/s390/net/qeth_l3_main.c b/drivers/s390/net/qeth_l3_main.c index d138ac432d01..8d474179ce98 100644 --- a/drivers/s390/net/qeth_l3_main.c +++ b/drivers/s390/net/qeth_l3_main.c @@ -1970,8 +1970,11 @@ static void qeth_l3_remove_device(struct ccwgroup_device *cgdev) 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 (card->dev->reg_state == NETREG_REGISTERED)