Commit 0b9902c1 authored by Julian Wiedmann's avatar Julian Wiedmann Committed by Jakub Kicinski
Browse files

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: 9dc48ccc ("qeth: serialize sysfs-triggered device configurations")
Signed-off-by: default avatarJulian Wiedmann <jwi@linux.ibm.com>
Reviewed-by: default avatarAlexandra Winter <wintera@linux.ibm.com>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent d7083427

drivers/s390/net/qeth_core.h

+2 −1
Original line number Diff line number Diff line
@@ -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)

drivers/s390/net/qeth_core_main.c

+22 −13
Original line number Diff line number Diff line
@@ -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)

drivers/s390/net/qeth_l2_main.c

+5 −2
Original line number Diff line number Diff line
@@ -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)

drivers/s390/net/qeth_l3_main.c

+5 −2
Original line number Diff line number Diff line
@@ -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)