Revision 774a1221e862b343388347bac9b318767336b20b authored by Tejun Heo on 16 January 2013, 02:52:51 UTC, committed by Linus Torvalds on 16 January 2013, 17:05:33 UTC
If the default iosched is built as module, the kernel may deadlock while trying to load the iosched module on device probe if the probing was running off async. This is because async_synchronize_full() at the end of module init ends up waiting for the async job which initiated the module loading. async A modprobe 1. finds a device 2. registers the block device 3. request_module(default iosched) 4. modprobe in userland 5. load and init module 6. async_synchronize_full() Async A waits for modprobe to finish in request_module() and modprobe waits for async A to finish in async_synchronize_full(). Because there's no easy to track dependency once control goes out to userland, implementing properly nested flushing is difficult. For now, make module init perform async_synchronize_full() iff module init has queued async jobs as suggested by Linus. This avoids the described deadlock because iosched module doesn't use async and thus wouldn't invoke async_synchronize_full(). This is hacky and incomplete. It will deadlock if async module loading nests; however, this works around the known problem case and seems to be the best of bad options. For more details, please refer to the following thread. http://thread.gmane.org/gmane.linux.kernel/1420814 Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Alex Riesen <raa.lkml@gmail.com> Tested-by: Ming Lei <ming.lei@canonical.com> Tested-by: Alex Riesen <raa.lkml@gmail.com> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 406089d
br_sysfs_if.c
/*
* Sysfs attributes of bridge ports
* Linux ethernet bridge
*
* Authors:
* Stephen Hemminger <shemminger@osdl.org>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/capability.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/if_bridge.h>
#include <linux/rtnetlink.h>
#include <linux/spinlock.h>
#include "br_private.h"
struct brport_attribute {
struct attribute attr;
ssize_t (*show)(struct net_bridge_port *, char *);
int (*store)(struct net_bridge_port *, unsigned long);
};
#define BRPORT_ATTR(_name,_mode,_show,_store) \
const struct brport_attribute brport_attr_##_name = { \
.attr = {.name = __stringify(_name), \
.mode = _mode }, \
.show = _show, \
.store = _store, \
};
#define BRPORT_ATTR_FLAG(_name, _mask) \
static ssize_t show_##_name(struct net_bridge_port *p, char *buf) \
{ \
return sprintf(buf, "%d\n", !!(p->flags & _mask)); \
} \
static int store_##_name(struct net_bridge_port *p, unsigned long v) \
{ \
unsigned long flags = p->flags; \
if (v) \
flags |= _mask; \
else \
flags &= ~_mask; \
if (flags != p->flags) { \
p->flags = flags; \
br_ifinfo_notify(RTM_NEWLINK, p); \
} \
return 0; \
} \
static BRPORT_ATTR(_name, S_IRUGO | S_IWUSR, \
show_##_name, store_##_name)
static ssize_t show_path_cost(struct net_bridge_port *p, char *buf)
{
return sprintf(buf, "%d\n", p->path_cost);
}
static BRPORT_ATTR(path_cost, S_IRUGO | S_IWUSR,
show_path_cost, br_stp_set_path_cost);
static ssize_t show_priority(struct net_bridge_port *p, char *buf)
{
return sprintf(buf, "%d\n", p->priority);
}
static BRPORT_ATTR(priority, S_IRUGO | S_IWUSR,
show_priority, br_stp_set_port_priority);
static ssize_t show_designated_root(struct net_bridge_port *p, char *buf)
{
return br_show_bridge_id(buf, &p->designated_root);
}
static BRPORT_ATTR(designated_root, S_IRUGO, show_designated_root, NULL);
static ssize_t show_designated_bridge(struct net_bridge_port *p, char *buf)
{
return br_show_bridge_id(buf, &p->designated_bridge);
}
static BRPORT_ATTR(designated_bridge, S_IRUGO, show_designated_bridge, NULL);
static ssize_t show_designated_port(struct net_bridge_port *p, char *buf)
{
return sprintf(buf, "%d\n", p->designated_port);
}
static BRPORT_ATTR(designated_port, S_IRUGO, show_designated_port, NULL);
static ssize_t show_designated_cost(struct net_bridge_port *p, char *buf)
{
return sprintf(buf, "%d\n", p->designated_cost);
}
static BRPORT_ATTR(designated_cost, S_IRUGO, show_designated_cost, NULL);
static ssize_t show_port_id(struct net_bridge_port *p, char *buf)
{
return sprintf(buf, "0x%x\n", p->port_id);
}
static BRPORT_ATTR(port_id, S_IRUGO, show_port_id, NULL);
static ssize_t show_port_no(struct net_bridge_port *p, char *buf)
{
return sprintf(buf, "0x%x\n", p->port_no);
}
static BRPORT_ATTR(port_no, S_IRUGO, show_port_no, NULL);
static ssize_t show_change_ack(struct net_bridge_port *p, char *buf)
{
return sprintf(buf, "%d\n", p->topology_change_ack);
}
static BRPORT_ATTR(change_ack, S_IRUGO, show_change_ack, NULL);
static ssize_t show_config_pending(struct net_bridge_port *p, char *buf)
{
return sprintf(buf, "%d\n", p->config_pending);
}
static BRPORT_ATTR(config_pending, S_IRUGO, show_config_pending, NULL);
static ssize_t show_port_state(struct net_bridge_port *p, char *buf)
{
return sprintf(buf, "%d\n", p->state);
}
static BRPORT_ATTR(state, S_IRUGO, show_port_state, NULL);
static ssize_t show_message_age_timer(struct net_bridge_port *p,
char *buf)
{
return sprintf(buf, "%ld\n", br_timer_value(&p->message_age_timer));
}
static BRPORT_ATTR(message_age_timer, S_IRUGO, show_message_age_timer, NULL);
static ssize_t show_forward_delay_timer(struct net_bridge_port *p,
char *buf)
{
return sprintf(buf, "%ld\n", br_timer_value(&p->forward_delay_timer));
}
static BRPORT_ATTR(forward_delay_timer, S_IRUGO, show_forward_delay_timer, NULL);
static ssize_t show_hold_timer(struct net_bridge_port *p,
char *buf)
{
return sprintf(buf, "%ld\n", br_timer_value(&p->hold_timer));
}
static BRPORT_ATTR(hold_timer, S_IRUGO, show_hold_timer, NULL);
static int store_flush(struct net_bridge_port *p, unsigned long v)
{
br_fdb_delete_by_port(p->br, p, 0); // Don't delete local entry
return 0;
}
static BRPORT_ATTR(flush, S_IWUSR, NULL, store_flush);
BRPORT_ATTR_FLAG(hairpin_mode, BR_HAIRPIN_MODE);
BRPORT_ATTR_FLAG(bpdu_guard, BR_BPDU_GUARD);
BRPORT_ATTR_FLAG(root_block, BR_ROOT_BLOCK);
#ifdef CONFIG_BRIDGE_IGMP_SNOOPING
static ssize_t show_multicast_router(struct net_bridge_port *p, char *buf)
{
return sprintf(buf, "%d\n", p->multicast_router);
}
static int store_multicast_router(struct net_bridge_port *p,
unsigned long v)
{
return br_multicast_set_port_router(p, v);
}
static BRPORT_ATTR(multicast_router, S_IRUGO | S_IWUSR, show_multicast_router,
store_multicast_router);
BRPORT_ATTR_FLAG(multicast_fast_leave, BR_MULTICAST_FAST_LEAVE);
#endif
static const struct brport_attribute *brport_attrs[] = {
&brport_attr_path_cost,
&brport_attr_priority,
&brport_attr_port_id,
&brport_attr_port_no,
&brport_attr_designated_root,
&brport_attr_designated_bridge,
&brport_attr_designated_port,
&brport_attr_designated_cost,
&brport_attr_state,
&brport_attr_change_ack,
&brport_attr_config_pending,
&brport_attr_message_age_timer,
&brport_attr_forward_delay_timer,
&brport_attr_hold_timer,
&brport_attr_flush,
&brport_attr_hairpin_mode,
&brport_attr_bpdu_guard,
&brport_attr_root_block,
#ifdef CONFIG_BRIDGE_IGMP_SNOOPING
&brport_attr_multicast_router,
&brport_attr_multicast_fast_leave,
#endif
NULL
};
#define to_brport_attr(_at) container_of(_at, struct brport_attribute, attr)
#define to_brport(obj) container_of(obj, struct net_bridge_port, kobj)
static ssize_t brport_show(struct kobject * kobj,
struct attribute * attr, char * buf)
{
struct brport_attribute * brport_attr = to_brport_attr(attr);
struct net_bridge_port * p = to_brport(kobj);
return brport_attr->show(p, buf);
}
static ssize_t brport_store(struct kobject * kobj,
struct attribute * attr,
const char * buf, size_t count)
{
struct brport_attribute * brport_attr = to_brport_attr(attr);
struct net_bridge_port * p = to_brport(kobj);
ssize_t ret = -EINVAL;
char *endp;
unsigned long val;
if (!ns_capable(dev_net(p->dev)->user_ns, CAP_NET_ADMIN))
return -EPERM;
val = simple_strtoul(buf, &endp, 0);
if (endp != buf) {
if (!rtnl_trylock())
return restart_syscall();
if (p->dev && p->br && brport_attr->store) {
spin_lock_bh(&p->br->lock);
ret = brport_attr->store(p, val);
spin_unlock_bh(&p->br->lock);
if (ret == 0)
ret = count;
}
rtnl_unlock();
}
return ret;
}
const struct sysfs_ops brport_sysfs_ops = {
.show = brport_show,
.store = brport_store,
};
/*
* Add sysfs entries to ethernet device added to a bridge.
* Creates a brport subdirectory with bridge attributes.
* Puts symlink in bridge's brif subdirectory
*/
int br_sysfs_addif(struct net_bridge_port *p)
{
struct net_bridge *br = p->br;
const struct brport_attribute **a;
int err;
err = sysfs_create_link(&p->kobj, &br->dev->dev.kobj,
SYSFS_BRIDGE_PORT_LINK);
if (err)
return err;
for (a = brport_attrs; *a; ++a) {
err = sysfs_create_file(&p->kobj, &((*a)->attr));
if (err)
return err;
}
strlcpy(p->sysfs_name, p->dev->name, IFNAMSIZ);
return sysfs_create_link(br->ifobj, &p->kobj, p->sysfs_name);
}
/* Rename bridge's brif symlink */
int br_sysfs_renameif(struct net_bridge_port *p)
{
struct net_bridge *br = p->br;
int err;
/* If a rename fails, the rollback will cause another
* rename call with the existing name.
*/
if (!strncmp(p->sysfs_name, p->dev->name, IFNAMSIZ))
return 0;
err = sysfs_rename_link(br->ifobj, &p->kobj,
p->sysfs_name, p->dev->name);
if (err)
netdev_notice(br->dev, "unable to rename link %s to %s",
p->sysfs_name, p->dev->name);
else
strlcpy(p->sysfs_name, p->dev->name, IFNAMSIZ);
return err;
}
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