From 0b9902c1fcc59ba75268386c0420a554f8844168 Mon Sep 17 00:00:00 2001 From: Julian Wiedmann Date: Thu, 7 Jan 2021 18:24:40 +0100 Subject: 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 Reviewed-by: Alexandra Winter Signed-off-by: Jakub Kicinski --- drivers/s390/net/qeth_l2_main.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'drivers/s390/net/qeth_l2_main.c') 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) -- cgit v1.2.3