linux/net/tipc/bearer.h
Erik Hugne 512137eeff tipc: remove interface state mirroring in bearer
struct 'tipc_bearer' is a generic representation of the underlying
media type, and exists in a one-to-one relationship to each interface
TIPC is using. The struct contains a 'blocked' flag that mirrors the
operational and execution state of the represented interface, and is
updated through notification calls from the latter. The users of
tipc_bearer are checking this flag before each attempt to send a
packet via the interface.

This state mirroring serves no purpose in the current code base. TIPC
links will not discover a media failure any faster through this
mechanism, and in reality the flag only adds overhead at packet
sending and reception.

Furthermore, the fact that the flag needs to be protected by a spinlock
aggregated into tipc_bearer has turned out to cause a serious and
completely unnecessary deadlock problem.

CPU0                                    CPU1
----                                    ----
Time 0: bearer_disable()                link_timeout()
Time 1:   spin_lock_bh(&b_ptr->lock)      tipc_link_push_queue()
Time 2:   tipc_link_delete()                tipc_bearer_blocked(b_ptr)
Time 3:     k_cancel_timer(&req->timer)       spin_lock_bh(&b_ptr->lock)
Time 4:       del_timer_sync(&req->timer)

I.e., del_timer_sync() on CPU0 never returns, because the timer handler
on CPU1 is waiting for the bearer lock.

We eliminate the 'blocked' flag from struct tipc_bearer, along with all
tests on this flag. This not only resolves the deadlock, but also
simplifies and speeds up the data path execution of TIPC. It also fits
well into our ongoing effort to make the locking policy simpler and
more manageable.

An effect of this change is that we can get rid of functions such as
tipc_bearer_blocked(), tipc_continue() and tipc_block_bearer().
We replace the latter with a new function, tipc_reset_bearer(), which
resets all links associated to the bearer immediately after an
interface goes down.

A user might notice one slight change in link behaviour after this
change. When an interface goes down, (e.g. through a NETDEV_DOWN
event) all attached links will be reset immediately, instead of
leaving it to each link to detect the failure through a timer-driven
mechanism. We consider this an improvement, and see no obvious risks
with the new behavior.

Signed-off-by: Erik Hugne <erik.hugne@ericsson.com>
Reviewed-by: Ying Xue <ying.xue@windriver.com>
Reviewed-by: Paul Gortmaker <Paul.Gortmaker@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2013-12-09 20:30:29 -05:00

210 lines
7.3 KiB
C

/*
* net/tipc/bearer.h: Include file for TIPC bearer code
*
* Copyright (c) 1996-2006, Ericsson AB
* Copyright (c) 2005, 2010-2011, Wind River Systems
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the names of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* Alternatively, this software may be distributed under the terms of the
* GNU General Public License ("GPL") version 2 as published by the Free
* Software Foundation.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef _TIPC_BEARER_H
#define _TIPC_BEARER_H
#include "bcast.h"
#define MAX_BEARERS 2
#define MAX_MEDIA 2
/*
* Identifiers associated with TIPC message header media address info
*
* - address info field is 20 bytes long
* - media type identifier located at offset 3
* - remaining bytes vary according to media type
*/
#define TIPC_MEDIA_ADDR_SIZE 20
#define TIPC_MEDIA_TYPE_OFFSET 3
/*
* Identifiers of supported TIPC media types
*/
#define TIPC_MEDIA_TYPE_ETH 1
#define TIPC_MEDIA_TYPE_IB 2
/**
* struct tipc_media_addr - destination address used by TIPC bearers
* @value: address info (format defined by media)
* @media_id: TIPC media type identifier
* @broadcast: non-zero if address is a broadcast address
*/
struct tipc_media_addr {
u8 value[TIPC_MEDIA_ADDR_SIZE];
u8 media_id;
u8 broadcast;
};
struct tipc_bearer;
/**
* struct tipc_media - TIPC media information available to internal users
* @send_msg: routine which handles buffer transmission
* @enable_media: routine which enables a media
* @disable_media: routine which disables a media
* @addr2str: routine which converts media address to string
* @addr2msg: routine which converts media address to protocol message area
* @msg2addr: routine which converts media address from protocol message area
* @bcast_addr: media address used in broadcasting
* @priority: default link (and bearer) priority
* @tolerance: default time (in ms) before declaring link failure
* @window: default window (in packets) before declaring link congestion
* @type_id: TIPC media identifier
* @name: media name
*/
struct tipc_media {
int (*send_msg)(struct sk_buff *buf,
struct tipc_bearer *b_ptr,
struct tipc_media_addr *dest);
int (*enable_media)(struct tipc_bearer *b_ptr);
void (*disable_media)(struct tipc_bearer *b_ptr);
int (*addr2str)(struct tipc_media_addr *a, char *str_buf, int str_size);
int (*addr2msg)(struct tipc_media_addr *a, char *msg_area);
int (*msg2addr)(const struct tipc_bearer *b_ptr,
struct tipc_media_addr *a, char *msg_area);
u32 priority;
u32 tolerance;
u32 window;
u32 type_id;
char name[TIPC_MAX_MEDIA_NAME];
};
/**
* struct tipc_bearer - TIPC bearer structure
* @usr_handle: pointer to additional media-specific information about bearer
* @mtu: max packet size bearer can support
* @lock: spinlock for controlling access to bearer
* @addr: media-specific address associated with bearer
* @name: bearer name (format = media:interface)
* @media: ptr to media structure associated with bearer
* @priority: default link priority for bearer
* @window: default window size for bearer
* @tolerance: default link tolerance for bearer
* @identity: array index of this bearer within TIPC bearer array
* @link_req: ptr to (optional) structure making periodic link setup requests
* @links: list of non-congested links associated with bearer
* @active: non-zero if bearer structure is represents a bearer
* @net_plane: network plane ('A' through 'H') currently associated with bearer
* @nodes: indicates which nodes in cluster can be reached through bearer
*
* Note: media-specific code is responsible for initialization of the fields
* indicated below when a bearer is enabled; TIPC's generic bearer code takes
* care of initializing all other fields.
*/
struct tipc_bearer {
void *usr_handle; /* initalized by media */
u32 mtu; /* initalized by media */
struct tipc_media_addr addr; /* initalized by media */
char name[TIPC_MAX_BEARER_NAME];
spinlock_t lock;
struct tipc_media *media;
struct tipc_media_addr bcast_addr;
u32 priority;
u32 window;
u32 tolerance;
u32 identity;
struct tipc_link_req *link_req;
struct list_head links;
int active;
char net_plane;
struct tipc_node_map nodes;
};
struct tipc_bearer_names {
char media_name[TIPC_MAX_MEDIA_NAME];
char if_name[TIPC_MAX_IF_NAME];
};
struct tipc_link;
extern struct tipc_bearer tipc_bearers[];
/*
* TIPC routines available to supported media types
*/
int tipc_register_media(struct tipc_media *m_ptr);
void tipc_recv_msg(struct sk_buff *buf, struct tipc_bearer *tb_ptr);
int tipc_reset_bearer(struct tipc_bearer *b_ptr);
int tipc_enable_bearer(const char *bearer_name, u32 disc_domain, u32 priority);
int tipc_disable_bearer(const char *name);
/*
* Routines made available to TIPC by supported media types
*/
int tipc_eth_media_start(void);
void tipc_eth_media_stop(void);
#ifdef CONFIG_TIPC_MEDIA_IB
int tipc_ib_media_start(void);
void tipc_ib_media_stop(void);
#else
static inline int tipc_ib_media_start(void) { return 0; }
static inline void tipc_ib_media_stop(void) { return; }
#endif
int tipc_media_set_priority(const char *name, u32 new_value);
int tipc_media_set_window(const char *name, u32 new_value);
void tipc_media_addr_printf(char *buf, int len, struct tipc_media_addr *a);
struct sk_buff *tipc_media_get_names(void);
struct sk_buff *tipc_bearer_get_names(void);
void tipc_bearer_add_dest(struct tipc_bearer *b_ptr, u32 dest);
void tipc_bearer_remove_dest(struct tipc_bearer *b_ptr, u32 dest);
struct tipc_bearer *tipc_bearer_find(const char *name);
struct tipc_bearer *tipc_bearer_find_interface(const char *if_name);
struct tipc_media *tipc_media_find(const char *name);
void tipc_bearer_stop(void);
/**
* tipc_bearer_send- sends buffer to destination over bearer
*
* IMPORTANT:
* The media send routine must not alter the buffer being passed in
* as it may be needed for later retransmission!
*/
static inline void tipc_bearer_send(struct tipc_bearer *b, struct sk_buff *buf,
struct tipc_media_addr *dest)
{
b->media->send_msg(buf, b, dest);
}
#endif /* _TIPC_BEARER_H */