kernel-fxtec-pro1x/drivers/net/caif/caif_serial.c
Linus Torvalds 55db4c64ed Revert "tty: make receive_buf() return the amout of bytes received"
This reverts commit b1c43f82c5.

It was broken in so many ways, and results in random odd pty issues.

It re-introduced the buggy schedule_work() in flush_to_ldisc() that can
cause endless work-loops (see commit a5660b41af: "tty: fix endless
work loop when the buffer fills up").

It also used an "unsigned int" return value fo the ->receive_buf()
function, but then made multiple functions return a negative error code,
and didn't actually check for the error in the caller.

And it didn't actually work at all.  BenH bisected down odd tty behavior
to it:
  "It looks like the patch is causing some major malfunctions of the X
   server for me, possibly related to PTYs.  For example, cat'ing a
   large file in a gnome terminal hangs the kernel for -minutes- in a
   loop of what looks like flush_to_ldisc/workqueue code, (some ftrace
   data in the quoted bits further down).

   ...

   Some more data: It -looks- like what happens is that the
   flush_to_ldisc work queue entry constantly re-queues itself (because
   the PTY is full ?) and the workqueue thread will basically loop
   forver calling it without ever scheduling, thus starving the consumer
   process that could have emptied the PTY."

which is pretty much exactly the problem we fixed in a5660b41af.

Milton Miller pointed out the 'unsigned int' issue.

Reported-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reported-by: Milton Miller <miltonm@bga.com>
Cc: Stefan Bigler <stefan.bigler@keymile.com>
Cc: Toby Gray <toby.gray@realvnc.com>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-06-04 06:33:24 +09:00

455 lines
10 KiB
C

/*
* Copyright (C) ST-Ericsson AB 2010
* Author: Sjur Brendeland / sjur.brandeland@stericsson.com
* License terms: GNU General Public License (GPL) version 2
*/
#include <linux/init.h>
#include <linux/version.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/types.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/rtnetlink.h>
#include <linux/tty.h>
#include <linux/file.h>
#include <linux/if_arp.h>
#include <net/caif/caif_device.h>
#include <net/caif/cfcnfg.h>
#include <linux/err.h>
#include <linux/debugfs.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Sjur Brendeland<sjur.brandeland@stericsson.com>");
MODULE_DESCRIPTION("CAIF serial device TTY line discipline");
MODULE_LICENSE("GPL");
MODULE_ALIAS_LDISC(N_CAIF);
#define SEND_QUEUE_LOW 10
#define SEND_QUEUE_HIGH 100
#define CAIF_SENDING 1 /* Bit 1 = 0x02*/
#define CAIF_FLOW_OFF_SENT 4 /* Bit 4 = 0x10 */
#define MAX_WRITE_CHUNK 4096
#define ON 1
#define OFF 0
#define CAIF_MAX_MTU 4096
/*This list is protected by the rtnl lock. */
static LIST_HEAD(ser_list);
static int ser_loop;
module_param(ser_loop, bool, S_IRUGO);
MODULE_PARM_DESC(ser_loop, "Run in simulated loopback mode.");
static int ser_use_stx = 1;
module_param(ser_use_stx, bool, S_IRUGO);
MODULE_PARM_DESC(ser_use_stx, "STX enabled or not.");
static int ser_use_fcs = 1;
module_param(ser_use_fcs, bool, S_IRUGO);
MODULE_PARM_DESC(ser_use_fcs, "FCS enabled or not.");
static int ser_write_chunk = MAX_WRITE_CHUNK;
module_param(ser_write_chunk, int, S_IRUGO);
MODULE_PARM_DESC(ser_write_chunk, "Maximum size of data written to UART.");
static struct dentry *debugfsdir;
static int caif_net_open(struct net_device *dev);
static int caif_net_close(struct net_device *dev);
struct ser_device {
struct caif_dev_common common;
struct list_head node;
struct net_device *dev;
struct sk_buff_head head;
struct tty_struct *tty;
bool tx_started;
unsigned long state;
char *tty_name;
#ifdef CONFIG_DEBUG_FS
struct dentry *debugfs_tty_dir;
struct debugfs_blob_wrapper tx_blob;
struct debugfs_blob_wrapper rx_blob;
u8 rx_data[128];
u8 tx_data[128];
u8 tty_status;
#endif
};
static void caifdev_setup(struct net_device *dev);
static void ldisc_tx_wakeup(struct tty_struct *tty);
#ifdef CONFIG_DEBUG_FS
static inline void update_tty_status(struct ser_device *ser)
{
ser->tty_status =
ser->tty->stopped << 5 |
ser->tty->hw_stopped << 4 |
ser->tty->flow_stopped << 3 |
ser->tty->packet << 2 |
ser->tty->low_latency << 1 |
ser->tty->warned;
}
static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
{
ser->debugfs_tty_dir =
debugfs_create_dir(tty->name, debugfsdir);
if (!IS_ERR(ser->debugfs_tty_dir)) {
debugfs_create_blob("last_tx_msg", S_IRUSR,
ser->debugfs_tty_dir,
&ser->tx_blob);
debugfs_create_blob("last_rx_msg", S_IRUSR,
ser->debugfs_tty_dir,
&ser->rx_blob);
debugfs_create_x32("ser_state", S_IRUSR,
ser->debugfs_tty_dir,
(u32 *)&ser->state);
debugfs_create_x8("tty_status", S_IRUSR,
ser->debugfs_tty_dir,
&ser->tty_status);
}
ser->tx_blob.data = ser->tx_data;
ser->tx_blob.size = 0;
ser->rx_blob.data = ser->rx_data;
ser->rx_blob.size = 0;
}
static inline void debugfs_deinit(struct ser_device *ser)
{
debugfs_remove_recursive(ser->debugfs_tty_dir);
}
static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
{
if (size > sizeof(ser->rx_data))
size = sizeof(ser->rx_data);
memcpy(ser->rx_data, data, size);
ser->rx_blob.data = ser->rx_data;
ser->rx_blob.size = size;
}
static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
{
if (size > sizeof(ser->tx_data))
size = sizeof(ser->tx_data);
memcpy(ser->tx_data, data, size);
ser->tx_blob.data = ser->tx_data;
ser->tx_blob.size = size;
}
#else
static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
{
}
static inline void debugfs_deinit(struct ser_device *ser)
{
}
static inline void update_tty_status(struct ser_device *ser)
{
}
static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
{
}
static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
{
}
#endif
static void ldisc_receive(struct tty_struct *tty, const u8 *data,
char *flags, int count)
{
struct sk_buff *skb = NULL;
struct ser_device *ser;
int ret;
u8 *p;
ser = tty->disc_data;
/*
* NOTE: flags may contain information about break or overrun.
* This is not yet handled.
*/
/*
* Workaround for garbage at start of transmission,
* only enable if STX handling is not enabled.
*/
if (!ser->common.use_stx && !ser->tx_started) {
dev_info(&ser->dev->dev,
"Bytes received before initial transmission -"
"bytes discarded.\n");
return;
}
BUG_ON(ser->dev == NULL);
/* Get a suitable caif packet and copy in data. */
skb = netdev_alloc_skb(ser->dev, count+1);
if (skb == NULL)
return;
p = skb_put(skb, count);
memcpy(p, data, count);
skb->protocol = htons(ETH_P_CAIF);
skb_reset_mac_header(skb);
skb->dev = ser->dev;
debugfs_rx(ser, data, count);
/* Push received packet up the stack. */
ret = netif_rx_ni(skb);
if (!ret) {
ser->dev->stats.rx_packets++;
ser->dev->stats.rx_bytes += count;
} else
++ser->dev->stats.rx_dropped;
update_tty_status(ser);
}
static int handle_tx(struct ser_device *ser)
{
struct tty_struct *tty;
struct sk_buff *skb;
int tty_wr, len, room;
tty = ser->tty;
ser->tx_started = true;
/* Enter critical section */
if (test_and_set_bit(CAIF_SENDING, &ser->state))
return 0;
/* skb_peek is safe because handle_tx is called after skb_queue_tail */
while ((skb = skb_peek(&ser->head)) != NULL) {
/* Make sure you don't write too much */
len = skb->len;
room = tty_write_room(tty);
if (!room)
break;
if (room > ser_write_chunk)
room = ser_write_chunk;
if (len > room)
len = room;
/* Write to tty or loopback */
if (!ser_loop) {
tty_wr = tty->ops->write(tty, skb->data, len);
update_tty_status(ser);
} else {
tty_wr = len;
ldisc_receive(tty, skb->data, NULL, len);
}
ser->dev->stats.tx_packets++;
ser->dev->stats.tx_bytes += tty_wr;
/* Error on TTY ?! */
if (tty_wr < 0)
goto error;
/* Reduce buffer written, and discard if empty */
skb_pull(skb, tty_wr);
if (skb->len == 0) {
struct sk_buff *tmp = skb_dequeue(&ser->head);
BUG_ON(tmp != skb);
if (in_interrupt())
dev_kfree_skb_irq(skb);
else
kfree_skb(skb);
}
}
/* Send flow off if queue is empty */
if (ser->head.qlen <= SEND_QUEUE_LOW &&
test_and_clear_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
ser->common.flowctrl != NULL)
ser->common.flowctrl(ser->dev, ON);
clear_bit(CAIF_SENDING, &ser->state);
return 0;
error:
clear_bit(CAIF_SENDING, &ser->state);
return tty_wr;
}
static int caif_xmit(struct sk_buff *skb, struct net_device *dev)
{
struct ser_device *ser;
BUG_ON(dev == NULL);
ser = netdev_priv(dev);
/* Send flow off once, on high water mark */
if (ser->head.qlen > SEND_QUEUE_HIGH &&
!test_and_set_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
ser->common.flowctrl != NULL)
ser->common.flowctrl(ser->dev, OFF);
skb_queue_tail(&ser->head, skb);
return handle_tx(ser);
}
static void ldisc_tx_wakeup(struct tty_struct *tty)
{
struct ser_device *ser;
ser = tty->disc_data;
BUG_ON(ser == NULL);
BUG_ON(ser->tty != tty);
handle_tx(ser);
}
static int ldisc_open(struct tty_struct *tty)
{
struct ser_device *ser;
struct net_device *dev;
char name[64];
int result;
/* No write no play */
if (tty->ops->write == NULL)
return -EOPNOTSUPP;
if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG))
return -EPERM;
sprintf(name, "cf%s", tty->name);
dev = alloc_netdev(sizeof(*ser), name, caifdev_setup);
ser = netdev_priv(dev);
ser->tty = tty_kref_get(tty);
ser->dev = dev;
debugfs_init(ser, tty);
tty->receive_room = N_TTY_BUF_SIZE;
tty->disc_data = ser;
set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
rtnl_lock();
result = register_netdevice(dev);
if (result) {
rtnl_unlock();
free_netdev(dev);
return -ENODEV;
}
list_add(&ser->node, &ser_list);
rtnl_unlock();
netif_stop_queue(dev);
update_tty_status(ser);
return 0;
}
static void ldisc_close(struct tty_struct *tty)
{
struct ser_device *ser = tty->disc_data;
/* Remove may be called inside or outside of rtnl_lock */
int islocked = rtnl_is_locked();
if (!islocked)
rtnl_lock();
/* device is freed automagically by net-sysfs */
dev_close(ser->dev);
unregister_netdevice(ser->dev);
list_del(&ser->node);
debugfs_deinit(ser);
tty_kref_put(ser->tty);
if (!islocked)
rtnl_unlock();
}
/* The line discipline structure. */
static struct tty_ldisc_ops caif_ldisc = {
.owner = THIS_MODULE,
.magic = TTY_LDISC_MAGIC,
.name = "n_caif",
.open = ldisc_open,
.close = ldisc_close,
.receive_buf = ldisc_receive,
.write_wakeup = ldisc_tx_wakeup
};
static int register_ldisc(void)
{
int result;
result = tty_register_ldisc(N_CAIF, &caif_ldisc);
if (result < 0) {
pr_err("cannot register CAIF ldisc=%d err=%d\n", N_CAIF,
result);
return result;
}
return result;
}
static const struct net_device_ops netdev_ops = {
.ndo_open = caif_net_open,
.ndo_stop = caif_net_close,
.ndo_start_xmit = caif_xmit
};
static void caifdev_setup(struct net_device *dev)
{
struct ser_device *serdev = netdev_priv(dev);
dev->features = 0;
dev->netdev_ops = &netdev_ops;
dev->type = ARPHRD_CAIF;
dev->flags = IFF_POINTOPOINT | IFF_NOARP;
dev->mtu = CAIF_MAX_MTU;
dev->tx_queue_len = 0;
dev->destructor = free_netdev;
skb_queue_head_init(&serdev->head);
serdev->common.link_select = CAIF_LINK_LOW_LATENCY;
serdev->common.use_frag = true;
serdev->common.use_stx = ser_use_stx;
serdev->common.use_fcs = ser_use_fcs;
serdev->dev = dev;
}
static int caif_net_open(struct net_device *dev)
{
netif_wake_queue(dev);
return 0;
}
static int caif_net_close(struct net_device *dev)
{
netif_stop_queue(dev);
return 0;
}
static int __init caif_ser_init(void)
{
int ret;
ret = register_ldisc();
debugfsdir = debugfs_create_dir("caif_serial", NULL);
return ret;
}
static void __exit caif_ser_exit(void)
{
struct ser_device *ser = NULL;
struct list_head *node;
struct list_head *_tmp;
list_for_each_safe(node, _tmp, &ser_list) {
ser = list_entry(node, struct ser_device, node);
dev_close(ser->dev);
unregister_netdevice(ser->dev);
list_del(node);
}
tty_unregister_ldisc(N_CAIF);
debugfs_remove_recursive(debugfsdir);
}
module_init(caif_ser_init);
module_exit(caif_ser_exit);