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Subject[134/262] jsm: remove buggy write queue
3.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Thadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com>

commit 9d898966c4a07e4a5092215b5a2829d0ef02baa2 upstream.

jsm uses a write queue that copies from uart_core circular buffer. This
copying however has some bugs, like not wrapping the head counter. Since
this write queue is also a circular buffer, the consumer function is
ready to use the uart_core circular buffer directly.

This buggy copying function was making some bytes be dropped when
transmitting to a raw tty, doing something like this.

[root@hostname ~]$ cat /dev/ttyn1 > cascardo/dump &
[1] 2658
[root@hostname ~]$ cat /proc/tty/drivers > /dev/ttyn0
[root@hostname ~]$ cat /proc/tty/drivers
/dev/tty /dev/tty 5 0 system:/dev/tty
/dev/console /dev/console 5 1 system:console
/dev/ptmx /dev/ptmx 5 2 system
/dev/vc/0 /dev/vc/0 4 0 system:vtmaster
jsm /dev/ttyn 250 0-31 serial
serial /dev/ttyS 4 64-95 serial
hvc /dev/hvc 229 0-7 system
pty_slave /dev/pts 136 0-1048575 pty:slave
pty_master /dev/ptm 128 0-1048575 pty:master
unknown /dev/tty 4 1-63 console
[root@hostname ~]$ cat cascardo/dump
/dev/tty /dev/tty 5 0 system:/dev/tty
/dev/console /dev/console 5 1 system:console
/dev/ptmx /dev/ptmx 5 2 system
/dev/vc/0 /dev/vc/0 4 0 system:vtmaste[root@hostname ~]$

This patch drops the driver write queue entirely, using the circular
buffer from uart_core only.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/tty/serial/jsm/jsm.h | 7 --
drivers/tty/serial/jsm/jsm_driver.c | 1
drivers/tty/serial/jsm/jsm_neo.c | 29 +++++------
drivers/tty/serial/jsm/jsm_tty.c | 94 ++++--------------------------------
4 files changed, 28 insertions(+), 103 deletions(-)

--- a/drivers/tty/serial/jsm/jsm.h
+++ b/drivers/tty/serial/jsm/jsm.h
@@ -183,10 +183,8 @@ struct jsm_board
/* Our Read/Error/Write queue sizes */
#define RQUEUEMASK 0x1FFF /* 8 K - 1 */
#define EQUEUEMASK 0x1FFF /* 8 K - 1 */
-#define WQUEUEMASK 0x0FFF /* 4 K - 1 */
#define RQUEUESIZE (RQUEUEMASK + 1)
#define EQUEUESIZE RQUEUESIZE
-#define WQUEUESIZE (WQUEUEMASK + 1)


/************************************************************************
@@ -226,10 +224,6 @@ struct jsm_channel {
u16 ch_e_head; /* Head location of the error queue */
u16 ch_e_tail; /* Tail location of the error queue */

- u8 *ch_wqueue; /* Our write queue buffer - malloc'ed */
- u16 ch_w_head; /* Head location of the write queue */
- u16 ch_w_tail; /* Tail location of the write queue */
-
u64 ch_rxcount; /* total of data received so far */
u64 ch_txcount; /* total of data transmitted so far */

@@ -378,7 +372,6 @@ extern int jsm_debug;
* Prototypes for non-static functions used in more than one module
*
*************************************************************************/
-int jsm_tty_write(struct uart_port *port);
int jsm_tty_init(struct jsm_board *);
int jsm_uart_port_init(struct jsm_board *);
int jsm_remove_uart_port(struct jsm_board *);
--- a/drivers/tty/serial/jsm/jsm_driver.c
+++ b/drivers/tty/serial/jsm/jsm_driver.c
@@ -211,7 +211,6 @@ static void __devexit jsm_remove_one(str
if (brd->channels[i]) {
kfree(brd->channels[i]->ch_rqueue);
kfree(brd->channels[i]->ch_equeue);
- kfree(brd->channels[i]->ch_wqueue);
kfree(brd->channels[i]);
}
}
--- a/drivers/tty/serial/jsm/jsm_neo.c
+++ b/drivers/tty/serial/jsm/jsm_neo.c
@@ -496,12 +496,15 @@ static void neo_copy_data_from_queue_to_
int s;
int qlen;
u32 len_written = 0;
+ struct circ_buf *circ;

if (!ch)
return;

+ circ = &ch->uart_port.state->xmit;
+
/* No data to write to the UART */
- if (ch->ch_w_tail == ch->ch_w_head)
+ if (uart_circ_empty(circ))
return;

/* If port is "stopped", don't send any data to the UART */
@@ -517,11 +520,10 @@ static void neo_copy_data_from_queue_to_
if (ch->ch_cached_lsr & UART_LSR_THRE) {
ch->ch_cached_lsr &= ~(UART_LSR_THRE);

- writeb(ch->ch_wqueue[ch->ch_w_tail], &ch->ch_neo_uart->txrx);
+ writeb(circ->buf[circ->tail], &ch->ch_neo_uart->txrx);
jsm_printk(WRITE, INFO, &ch->ch_bd->pci_dev,
- "Tx data: %x\n", ch->ch_wqueue[ch->ch_w_head]);
- ch->ch_w_tail++;
- ch->ch_w_tail &= WQUEUEMASK;
+ "Tx data: %x\n", circ->buf[circ->head]);
+ circ->tail = (circ->tail + 1) & (UART_XMIT_SIZE - 1);
ch->ch_txcount++;
}
return;
@@ -536,36 +538,36 @@ static void neo_copy_data_from_queue_to_
n = UART_17158_TX_FIFOSIZE - ch->ch_t_tlevel;

/* cache head and tail of queue */
- head = ch->ch_w_head & WQUEUEMASK;
- tail = ch->ch_w_tail & WQUEUEMASK;
- qlen = (head - tail) & WQUEUEMASK;
+ head = circ->head & (UART_XMIT_SIZE - 1);
+ tail = circ->tail & (UART_XMIT_SIZE - 1);
+ qlen = uart_circ_chars_pending(circ);

/* Find minimum of the FIFO space, versus queue length */
n = min(n, qlen);

while (n > 0) {

- s = ((head >= tail) ? head : WQUEUESIZE) - tail;
+ s = ((head >= tail) ? head : UART_XMIT_SIZE) - tail;
s = min(s, n);

if (s <= 0)
break;

- memcpy_toio(&ch->ch_neo_uart->txrxburst, ch->ch_wqueue + tail, s);
+ memcpy_toio(&ch->ch_neo_uart->txrxburst, circ->buf + tail, s);
/* Add and flip queue if needed */
- tail = (tail + s) & WQUEUEMASK;
+ tail = (tail + s) & (UART_XMIT_SIZE - 1);
n -= s;
ch->ch_txcount += s;
len_written += s;
}

/* Update the final tail */
- ch->ch_w_tail = tail & WQUEUEMASK;
+ circ->tail = tail & (UART_XMIT_SIZE - 1);

if (len_written >= ch->ch_t_tlevel)
ch->ch_flags &= ~(CH_TX_FIFO_EMPTY | CH_TX_FIFO_LWM);

- if (!jsm_tty_write(&ch->uart_port))
+ if (uart_circ_empty(circ))
uart_write_wakeup(&ch->uart_port);
}

@@ -946,7 +948,6 @@ static void neo_param(struct jsm_channel
if ((ch->ch_c_cflag & (CBAUD)) == 0) {
ch->ch_r_head = ch->ch_r_tail = 0;
ch->ch_e_head = ch->ch_e_tail = 0;
- ch->ch_w_head = ch->ch_w_tail = 0;

neo_flush_uart_write(ch);
neo_flush_uart_read(ch);
--- a/drivers/tty/serial/jsm/jsm_tty.c
+++ b/drivers/tty/serial/jsm/jsm_tty.c
@@ -118,6 +118,19 @@ static void jsm_tty_set_mctrl(struct uar
udelay(10);
}

+/*
+ * jsm_tty_write()
+ *
+ * Take data from the user or kernel and send it out to the FEP.
+ * In here exists all the Transparent Print magic as well.
+ */
+static void jsm_tty_write(struct uart_port *port)
+{
+ struct jsm_channel *channel;
+ channel = container_of(port, struct jsm_channel, uart_port);
+ channel->ch_bd->bd_ops->copy_data_from_queue_to_uart(channel);
+}
+
static void jsm_tty_start_tx(struct uart_port *port)
{
struct jsm_channel *channel = (struct jsm_channel *)port;
@@ -216,14 +229,6 @@ static int jsm_tty_open(struct uart_port
return -ENOMEM;
}
}
- if (!channel->ch_wqueue) {
- channel->ch_wqueue = kzalloc(WQUEUESIZE, GFP_KERNEL);
- if (!channel->ch_wqueue) {
- jsm_printk(INIT, ERR, &channel->ch_bd->pci_dev,
- "unable to allocate write queue buf");
- return -ENOMEM;
- }
- }

channel->ch_flags &= ~(CH_OPENING);
/*
@@ -237,7 +242,6 @@ static int jsm_tty_open(struct uart_port
*/
channel->ch_r_head = channel->ch_r_tail = 0;
channel->ch_e_head = channel->ch_e_tail = 0;
- channel->ch_w_head = channel->ch_w_tail = 0;

brd->bd_ops->flush_uart_write(channel);
brd->bd_ops->flush_uart_read(channel);
@@ -836,75 +840,3 @@ void jsm_check_queue_flow_control(struct
}
}
}
-
-/*
- * jsm_tty_write()
- *
- * Take data from the user or kernel and send it out to the FEP.
- * In here exists all the Transparent Print magic as well.
- */
-int jsm_tty_write(struct uart_port *port)
-{
- int bufcount;
- int data_count = 0,data_count1 =0;
- u16 head;
- u16 tail;
- u16 tmask;
- u32 remain;
- int temp_tail = port->state->xmit.tail;
- struct jsm_channel *channel = (struct jsm_channel *)port;
-
- tmask = WQUEUEMASK;
- head = (channel->ch_w_head) & tmask;
- tail = (channel->ch_w_tail) & tmask;
-
- if ((bufcount = tail - head - 1) < 0)
- bufcount += WQUEUESIZE;
-
- bufcount = min(bufcount, 56);
- remain = WQUEUESIZE - head;
-
- data_count = 0;
- if (bufcount >= remain) {
- bufcount -= remain;
- while ((port->state->xmit.head != temp_tail) &&
- (data_count < remain)) {
- channel->ch_wqueue[head++] =
- port->state->xmit.buf[temp_tail];
-
- temp_tail++;
- temp_tail &= (UART_XMIT_SIZE - 1);
- data_count++;
- }
- if (data_count == remain) head = 0;
- }
-
- data_count1 = 0;
- if (bufcount > 0) {
- remain = bufcount;
- while ((port->state->xmit.head != temp_tail) &&
- (data_count1 < remain)) {
- channel->ch_wqueue[head++] =
- port->state->xmit.buf[temp_tail];
-
- temp_tail++;
- temp_tail &= (UART_XMIT_SIZE - 1);
- data_count1++;
-
- }
- }
-
- port->state->xmit.tail = temp_tail;
-
- data_count += data_count1;
- if (data_count) {
- head &= tmask;
- channel->ch_w_head = head;
- }
-
- if (data_count) {
- channel->ch_bd->bd_ops->copy_data_from_queue_to_uart(channel);
- }
-
- return data_count;
-}



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