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s390/qeth: fix potential deadlock on workqueue flush 

The L2 bridgeport code uses the coarse 'conf_mutex' for guarding access
to its configuration state.
This can result in a deadlock when qeth_l2_stop_card() - called under the
conf_mutex - blocks on flush_workqueue() to wait for the completion of
pending bridgeport workers. Such workers would also need to aquire
the conf_mutex, stalling indefinitely.

Introduce a lock that specifically guards the bridgeport configuration,
so that the workers no longer need the conf_mutex.
Wrapping qeth_l2_promisc_to_bridge() in this fine-grained lock then also
fixes a theoretical race against a concurrent qeth_bridge_port_role_store()
operation.

Fixes: c0a2e4d10d ("s390/qeth: conclude all event processing before offlining a card")
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Reviewed-by: Alexandra Winter <wintera@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Julian Wiedmann 2019-11-20 14:20:56 +01:00 committed by David S. Miller
parent 004b39427f
commit c8183f5489
3 changed files with 28 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
drivers/s390/net/qeth_core.h
View File

@ -839,6 +839,7 @@ struct qeth_card {
struct service_level qeth_service_level;
struct qdio_ssqd_desc ssqd;
debug_info_t *debug;
struct mutex sbp_lock;
struct mutex conf_mutex;
struct mutex discipline_mutex;
struct napi_struct napi;

21
drivers/s390/net/qeth_l2_main.c
View File

@ -467,10 +467,14 @@ static void qeth_l2_set_promisc_mode(struct qeth_card *card)
if (card->info.promisc_mode == enable)
return;
if (qeth_adp_supported(card, IPA_SETADP_SET_PROMISC_MODE))
if (qeth_adp_supported(card, IPA_SETADP_SET_PROMISC_MODE)) {
qeth_setadp_promisc_mode(card, enable);
else if (card->options.sbp.reflect_promisc)
qeth_l2_promisc_to_bridge(card, enable);
} else {
mutex_lock(&card->sbp_lock);
if (card->options.sbp.reflect_promisc)
qeth_l2_promisc_to_bridge(card, enable);
mutex_unlock(&card->sbp_lock);
}
}
/* New MAC address is added to the hash table and marked to be written on card
@ -631,6 +635,7 @@ static int qeth_l2_probe_device(struct ccwgroup_device *gdev)
int rc;
qeth_l2_vnicc_set_defaults(card);
mutex_init(&card->sbp_lock);
if (gdev->dev.type == &qeth_generic_devtype) {
rc = qeth_l2_create_device_attributes(&gdev->dev);
@ -804,10 +809,12 @@ static int qeth_l2_set_online(struct ccwgroup_device *gdev)
} else
card->info.hwtrap = 0;
mutex_lock(&card->sbp_lock);
qeth_bridgeport_query_support(card);
if (card->options.sbp.supported_funcs)
dev_info(&card->gdev->dev,
"The device represents a Bridge Capable Port\n");
mutex_unlock(&card->sbp_lock);
qeth_l2_register_dev_addr(card);
@ -1162,9 +1169,9 @@ static void qeth_bridge_state_change_worker(struct work_struct *work)
/* Role should not change by itself, but if it did, */
/* information from the hardware is authoritative. */
mutex_lock(&data->card->conf_mutex);
mutex_lock(&data->card->sbp_lock);
data->card->options.sbp.role = entry->role;
mutex_unlock(&data->card->conf_mutex);
mutex_unlock(&data->card->sbp_lock);
snprintf(env_locrem, sizeof(env_locrem), "BRIDGEPORT=statechange");
snprintf(env_role, sizeof(env_role), "ROLE=%s",
@ -1230,9 +1237,9 @@ static void qeth_bridge_host_event_worker(struct work_struct *work)
: (data->hostevs.lost_event_mask == 0x02)
? "Bridge port state change"
: "Unknown reason");
mutex_lock(&data->card->conf_mutex);
mutex_lock(&data->card->sbp_lock);
data->card->options.sbp.hostnotification = 0;
mutex_unlock(&data->card->conf_mutex);
mutex_unlock(&data->card->sbp_lock);
qeth_bridge_emit_host_event(data->card, anev_abort,
0, NULL, NULL);
} else

14
drivers/s390/net/qeth_l2_sys.c
View File

@ -24,6 +24,7 @@ static ssize_t qeth_bridge_port_role_state_show(struct device *dev,
if (qeth_l2_vnicc_is_in_use(card))
return sprintf(buf, "n/a (VNIC characteristics)\n");
mutex_lock(&card->sbp_lock);
if (qeth_card_hw_is_reachable(card) &&
card->options.sbp.supported_funcs)
rc = qeth_bridgeport_query_ports(card,
@ -57,6 +58,7 @@ static ssize_t qeth_bridge_port_role_state_show(struct device *dev,
else
rc = sprintf(buf, "%s\n", word);
}
mutex_unlock(&card->sbp_lock);
return rc;
}
@ -91,6 +93,7 @@ static ssize_t qeth_bridge_port_role_store(struct device *dev,
return -EINVAL;
mutex_lock(&card->conf_mutex);
mutex_lock(&card->sbp_lock);
if (qeth_l2_vnicc_is_in_use(card))
rc = -EBUSY;
@ -104,6 +107,7 @@ static ssize_t qeth_bridge_port_role_store(struct device *dev,
} else
card->options.sbp.role = role;
mutex_unlock(&card->sbp_lock);
mutex_unlock(&card->conf_mutex);
return rc ? rc : count;
@ -158,6 +162,7 @@ static ssize_t qeth_bridgeport_hostnotification_store(struct device *dev,
return rc;
mutex_lock(&card->conf_mutex);
mutex_lock(&card->sbp_lock);
if (qeth_l2_vnicc_is_in_use(card))
rc = -EBUSY;
@ -168,6 +173,7 @@ static ssize_t qeth_bridgeport_hostnotification_store(struct device *dev,
} else
card->options.sbp.hostnotification = enable;
mutex_unlock(&card->sbp_lock);
mutex_unlock(&card->conf_mutex);
return rc ? rc : count;
@ -223,6 +229,7 @@ static ssize_t qeth_bridgeport_reflect_store(struct device *dev,
return -EINVAL;
mutex_lock(&card->conf_mutex);
mutex_lock(&card->sbp_lock);
if (qeth_l2_vnicc_is_in_use(card))
rc = -EBUSY;
@ -234,6 +241,7 @@ static ssize_t qeth_bridgeport_reflect_store(struct device *dev,
rc = 0;
}
mutex_unlock(&card->sbp_lock);
mutex_unlock(&card->conf_mutex);
return rc ? rc : count;
@ -269,6 +277,8 @@ void qeth_l2_setup_bridgeport_attrs(struct qeth_card *card)
return;
if (!card->options.sbp.supported_funcs)
return;
mutex_lock(&card->sbp_lock);
if (card->options.sbp.role != QETH_SBP_ROLE_NONE) {
/* Conditional to avoid spurious error messages */
qeth_bridgeport_setrole(card, card->options.sbp.role);
@ -280,8 +290,10 @@ void qeth_l2_setup_bridgeport_attrs(struct qeth_card *card)
rc = qeth_bridgeport_an_set(card, 1);
if (rc)
card->options.sbp.hostnotification = 0;
} else
} else {
qeth_bridgeport_an_set(card, 0);
}
mutex_unlock(&card->sbp_lock);
}
/* VNIC CHARS support */