forked from luck/tmp_suning_uos_patched
24a89d1cb6
Although line discipline receiving is single-producer/single-consumer, using tty->receive_room to manage flow control creates unnecessary critical regions requiring additional lock use. Instead, introduce the optional .receive_buf2() ldisc method which returns the # of bytes actually received. Serialization is guaranteed by the caller. In turn, the line discipline should schedule the buffer work item whenever space becomes available; ie., when there is room to receive data and receive_room() previously returned 0 (the buffer work item stops processing if receive_buf2() returns 0). Note the 'no room' state need not be atomic despite concurrent use by two threads because only the buffer work thread can set the state and only the read() thread can clear the state. Add n_tty_receive_buf2() as the receive_buf2() method for N_TTY. Provide a public helper function, tty_ldisc_receive_buf(), to use when directly accessing the receive_buf() methods. Line disciplines not using input flow control can continue to set tty->receive_room to a fixed value and only provide the receive_buf() method. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
559 lines
14 KiB
C
559 lines
14 KiB
C
/*
|
|
* Tty buffer allocation management
|
|
*/
|
|
|
|
#include <linux/types.h>
|
|
#include <linux/errno.h>
|
|
#include <linux/tty.h>
|
|
#include <linux/tty_driver.h>
|
|
#include <linux/tty_flip.h>
|
|
#include <linux/timer.h>
|
|
#include <linux/string.h>
|
|
#include <linux/slab.h>
|
|
#include <linux/sched.h>
|
|
#include <linux/init.h>
|
|
#include <linux/wait.h>
|
|
#include <linux/bitops.h>
|
|
#include <linux/delay.h>
|
|
#include <linux/module.h>
|
|
#include <linux/ratelimit.h>
|
|
|
|
/**
|
|
* tty_buffer_free_all - free buffers used by a tty
|
|
* @tty: tty to free from
|
|
*
|
|
* Remove all the buffers pending on a tty whether queued with data
|
|
* or in the free ring. Must be called when the tty is no longer in use
|
|
*
|
|
* Locking: none
|
|
*/
|
|
|
|
void tty_buffer_free_all(struct tty_port *port)
|
|
{
|
|
struct tty_bufhead *buf = &port->buf;
|
|
struct tty_buffer *thead;
|
|
|
|
while ((thead = buf->head) != NULL) {
|
|
buf->head = thead->next;
|
|
kfree(thead);
|
|
}
|
|
while ((thead = buf->free) != NULL) {
|
|
buf->free = thead->next;
|
|
kfree(thead);
|
|
}
|
|
buf->tail = NULL;
|
|
buf->memory_used = 0;
|
|
}
|
|
|
|
/**
|
|
* tty_buffer_alloc - allocate a tty buffer
|
|
* @tty: tty device
|
|
* @size: desired size (characters)
|
|
*
|
|
* Allocate a new tty buffer to hold the desired number of characters.
|
|
* Return NULL if out of memory or the allocation would exceed the
|
|
* per device queue
|
|
*
|
|
* Locking: Caller must hold tty->buf.lock
|
|
*/
|
|
|
|
static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size)
|
|
{
|
|
struct tty_buffer *p;
|
|
|
|
if (port->buf.memory_used + size > 65536)
|
|
return NULL;
|
|
p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC);
|
|
if (p == NULL)
|
|
return NULL;
|
|
p->used = 0;
|
|
p->size = size;
|
|
p->next = NULL;
|
|
p->commit = 0;
|
|
p->read = 0;
|
|
p->char_buf_ptr = (char *)(p->data);
|
|
p->flag_buf_ptr = (unsigned char *)p->char_buf_ptr + size;
|
|
port->buf.memory_used += size;
|
|
return p;
|
|
}
|
|
|
|
/**
|
|
* tty_buffer_free - free a tty buffer
|
|
* @tty: tty owning the buffer
|
|
* @b: the buffer to free
|
|
*
|
|
* Free a tty buffer, or add it to the free list according to our
|
|
* internal strategy
|
|
*
|
|
* Locking: Caller must hold tty->buf.lock
|
|
*/
|
|
|
|
static void tty_buffer_free(struct tty_port *port, struct tty_buffer *b)
|
|
{
|
|
struct tty_bufhead *buf = &port->buf;
|
|
|
|
/* Dumb strategy for now - should keep some stats */
|
|
buf->memory_used -= b->size;
|
|
WARN_ON(buf->memory_used < 0);
|
|
|
|
if (b->size >= 512)
|
|
kfree(b);
|
|
else {
|
|
b->next = buf->free;
|
|
buf->free = b;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* __tty_buffer_flush - flush full tty buffers
|
|
* @tty: tty to flush
|
|
*
|
|
* flush all the buffers containing receive data. Caller must
|
|
* hold the buffer lock and must have ensured no parallel flush to
|
|
* ldisc is running.
|
|
*
|
|
* Locking: Caller must hold tty->buf.lock
|
|
*/
|
|
|
|
static void __tty_buffer_flush(struct tty_port *port)
|
|
{
|
|
struct tty_bufhead *buf = &port->buf;
|
|
struct tty_buffer *thead;
|
|
|
|
if (unlikely(buf->head == NULL))
|
|
return;
|
|
while ((thead = buf->head->next) != NULL) {
|
|
tty_buffer_free(port, buf->head);
|
|
buf->head = thead;
|
|
}
|
|
WARN_ON(buf->head != buf->tail);
|
|
buf->head->read = buf->head->commit;
|
|
}
|
|
|
|
/**
|
|
* tty_buffer_flush - flush full tty buffers
|
|
* @tty: tty to flush
|
|
*
|
|
* flush all the buffers containing receive data. If the buffer is
|
|
* being processed by flush_to_ldisc then we defer the processing
|
|
* to that function
|
|
*
|
|
* Locking: none
|
|
*/
|
|
|
|
void tty_buffer_flush(struct tty_struct *tty)
|
|
{
|
|
struct tty_port *port = tty->port;
|
|
struct tty_bufhead *buf = &port->buf;
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&buf->lock, flags);
|
|
|
|
/* If the data is being pushed to the tty layer then we can't
|
|
process it here. Instead set a flag and the flush_to_ldisc
|
|
path will process the flush request before it exits */
|
|
if (test_bit(TTYP_FLUSHING, &port->iflags)) {
|
|
set_bit(TTYP_FLUSHPENDING, &port->iflags);
|
|
spin_unlock_irqrestore(&buf->lock, flags);
|
|
wait_event(tty->read_wait,
|
|
test_bit(TTYP_FLUSHPENDING, &port->iflags) == 0);
|
|
return;
|
|
} else
|
|
__tty_buffer_flush(port);
|
|
spin_unlock_irqrestore(&buf->lock, flags);
|
|
}
|
|
|
|
/**
|
|
* tty_buffer_find - find a free tty buffer
|
|
* @tty: tty owning the buffer
|
|
* @size: characters wanted
|
|
*
|
|
* Locate an existing suitable tty buffer or if we are lacking one then
|
|
* allocate a new one. We round our buffers off in 256 character chunks
|
|
* to get better allocation behaviour.
|
|
*
|
|
* Locking: Caller must hold tty->buf.lock
|
|
*/
|
|
|
|
static struct tty_buffer *tty_buffer_find(struct tty_port *port, size_t size)
|
|
{
|
|
struct tty_buffer **tbh = &port->buf.free;
|
|
while ((*tbh) != NULL) {
|
|
struct tty_buffer *t = *tbh;
|
|
if (t->size >= size) {
|
|
*tbh = t->next;
|
|
t->next = NULL;
|
|
t->used = 0;
|
|
t->commit = 0;
|
|
t->read = 0;
|
|
port->buf.memory_used += t->size;
|
|
return t;
|
|
}
|
|
tbh = &((*tbh)->next);
|
|
}
|
|
/* Round the buffer size out */
|
|
size = (size + 0xFF) & ~0xFF;
|
|
return tty_buffer_alloc(port, size);
|
|
/* Should possibly check if this fails for the largest buffer we
|
|
have queued and recycle that ? */
|
|
}
|
|
/**
|
|
* tty_buffer_request_room - grow tty buffer if needed
|
|
* @tty: tty structure
|
|
* @size: size desired
|
|
*
|
|
* Make at least size bytes of linear space available for the tty
|
|
* buffer. If we fail return the size we managed to find.
|
|
*
|
|
* Locking: Takes port->buf.lock
|
|
*/
|
|
int tty_buffer_request_room(struct tty_port *port, size_t size)
|
|
{
|
|
struct tty_bufhead *buf = &port->buf;
|
|
struct tty_buffer *b, *n;
|
|
int left;
|
|
unsigned long flags;
|
|
spin_lock_irqsave(&buf->lock, flags);
|
|
/* OPTIMISATION: We could keep a per tty "zero" sized buffer to
|
|
remove this conditional if its worth it. This would be invisible
|
|
to the callers */
|
|
b = buf->tail;
|
|
if (b != NULL)
|
|
left = b->size - b->used;
|
|
else
|
|
left = 0;
|
|
|
|
if (left < size) {
|
|
/* This is the slow path - looking for new buffers to use */
|
|
if ((n = tty_buffer_find(port, size)) != NULL) {
|
|
if (b != NULL) {
|
|
b->next = n;
|
|
b->commit = b->used;
|
|
} else
|
|
buf->head = n;
|
|
buf->tail = n;
|
|
} else
|
|
size = left;
|
|
}
|
|
spin_unlock_irqrestore(&buf->lock, flags);
|
|
return size;
|
|
}
|
|
EXPORT_SYMBOL_GPL(tty_buffer_request_room);
|
|
|
|
/**
|
|
* tty_insert_flip_string_fixed_flag - Add characters to the tty buffer
|
|
* @port: tty port
|
|
* @chars: characters
|
|
* @flag: flag value for each character
|
|
* @size: size
|
|
*
|
|
* Queue a series of bytes to the tty buffering. All the characters
|
|
* passed are marked with the supplied flag. Returns the number added.
|
|
*
|
|
* Locking: Called functions may take port->buf.lock
|
|
*/
|
|
|
|
int tty_insert_flip_string_fixed_flag(struct tty_port *port,
|
|
const unsigned char *chars, char flag, size_t size)
|
|
{
|
|
int copied = 0;
|
|
do {
|
|
int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
|
|
int space = tty_buffer_request_room(port, goal);
|
|
struct tty_buffer *tb = port->buf.tail;
|
|
/* If there is no space then tb may be NULL */
|
|
if (unlikely(space == 0)) {
|
|
break;
|
|
}
|
|
memcpy(tb->char_buf_ptr + tb->used, chars, space);
|
|
memset(tb->flag_buf_ptr + tb->used, flag, space);
|
|
tb->used += space;
|
|
copied += space;
|
|
chars += space;
|
|
/* There is a small chance that we need to split the data over
|
|
several buffers. If this is the case we must loop */
|
|
} while (unlikely(size > copied));
|
|
return copied;
|
|
}
|
|
EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag);
|
|
|
|
/**
|
|
* tty_insert_flip_string_flags - Add characters to the tty buffer
|
|
* @port: tty port
|
|
* @chars: characters
|
|
* @flags: flag bytes
|
|
* @size: size
|
|
*
|
|
* Queue a series of bytes to the tty buffering. For each character
|
|
* the flags array indicates the status of the character. Returns the
|
|
* number added.
|
|
*
|
|
* Locking: Called functions may take port->buf.lock
|
|
*/
|
|
|
|
int tty_insert_flip_string_flags(struct tty_port *port,
|
|
const unsigned char *chars, const char *flags, size_t size)
|
|
{
|
|
int copied = 0;
|
|
do {
|
|
int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
|
|
int space = tty_buffer_request_room(port, goal);
|
|
struct tty_buffer *tb = port->buf.tail;
|
|
/* If there is no space then tb may be NULL */
|
|
if (unlikely(space == 0)) {
|
|
break;
|
|
}
|
|
memcpy(tb->char_buf_ptr + tb->used, chars, space);
|
|
memcpy(tb->flag_buf_ptr + tb->used, flags, space);
|
|
tb->used += space;
|
|
copied += space;
|
|
chars += space;
|
|
flags += space;
|
|
/* There is a small chance that we need to split the data over
|
|
several buffers. If this is the case we must loop */
|
|
} while (unlikely(size > copied));
|
|
return copied;
|
|
}
|
|
EXPORT_SYMBOL(tty_insert_flip_string_flags);
|
|
|
|
/**
|
|
* tty_schedule_flip - push characters to ldisc
|
|
* @port: tty port to push from
|
|
*
|
|
* Takes any pending buffers and transfers their ownership to the
|
|
* ldisc side of the queue. It then schedules those characters for
|
|
* processing by the line discipline.
|
|
* Note that this function can only be used when the low_latency flag
|
|
* is unset. Otherwise the workqueue won't be flushed.
|
|
*
|
|
* Locking: Takes port->buf.lock
|
|
*/
|
|
|
|
void tty_schedule_flip(struct tty_port *port)
|
|
{
|
|
struct tty_bufhead *buf = &port->buf;
|
|
unsigned long flags;
|
|
WARN_ON(port->low_latency);
|
|
|
|
spin_lock_irqsave(&buf->lock, flags);
|
|
if (buf->tail != NULL)
|
|
buf->tail->commit = buf->tail->used;
|
|
spin_unlock_irqrestore(&buf->lock, flags);
|
|
schedule_work(&buf->work);
|
|
}
|
|
EXPORT_SYMBOL(tty_schedule_flip);
|
|
|
|
/**
|
|
* tty_prepare_flip_string - make room for characters
|
|
* @port: tty port
|
|
* @chars: return pointer for character write area
|
|
* @size: desired size
|
|
*
|
|
* Prepare a block of space in the buffer for data. Returns the length
|
|
* available and buffer pointer to the space which is now allocated and
|
|
* accounted for as ready for normal characters. This is used for drivers
|
|
* that need their own block copy routines into the buffer. There is no
|
|
* guarantee the buffer is a DMA target!
|
|
*
|
|
* Locking: May call functions taking port->buf.lock
|
|
*/
|
|
|
|
int tty_prepare_flip_string(struct tty_port *port, unsigned char **chars,
|
|
size_t size)
|
|
{
|
|
int space = tty_buffer_request_room(port, size);
|
|
if (likely(space)) {
|
|
struct tty_buffer *tb = port->buf.tail;
|
|
*chars = tb->char_buf_ptr + tb->used;
|
|
memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space);
|
|
tb->used += space;
|
|
}
|
|
return space;
|
|
}
|
|
EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
|
|
|
|
/**
|
|
* tty_prepare_flip_string_flags - make room for characters
|
|
* @port: tty port
|
|
* @chars: return pointer for character write area
|
|
* @flags: return pointer for status flag write area
|
|
* @size: desired size
|
|
*
|
|
* Prepare a block of space in the buffer for data. Returns the length
|
|
* available and buffer pointer to the space which is now allocated and
|
|
* accounted for as ready for characters. This is used for drivers
|
|
* that need their own block copy routines into the buffer. There is no
|
|
* guarantee the buffer is a DMA target!
|
|
*
|
|
* Locking: May call functions taking port->buf.lock
|
|
*/
|
|
|
|
int tty_prepare_flip_string_flags(struct tty_port *port,
|
|
unsigned char **chars, char **flags, size_t size)
|
|
{
|
|
int space = tty_buffer_request_room(port, size);
|
|
if (likely(space)) {
|
|
struct tty_buffer *tb = port->buf.tail;
|
|
*chars = tb->char_buf_ptr + tb->used;
|
|
*flags = tb->flag_buf_ptr + tb->used;
|
|
tb->used += space;
|
|
}
|
|
return space;
|
|
}
|
|
EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags);
|
|
|
|
|
|
static int
|
|
receive_buf(struct tty_struct *tty, struct tty_buffer *head, int count)
|
|
{
|
|
struct tty_ldisc *disc = tty->ldisc;
|
|
char *p = head->char_buf_ptr + head->read;
|
|
unsigned char *f = head->flag_buf_ptr + head->read;
|
|
|
|
if (disc->ops->receive_buf2)
|
|
count = disc->ops->receive_buf2(tty, p, f, count);
|
|
else {
|
|
count = min_t(int, count, tty->receive_room);
|
|
if (count)
|
|
disc->ops->receive_buf(tty, p, f, count);
|
|
}
|
|
head->read += count;
|
|
return count;
|
|
}
|
|
|
|
/**
|
|
* flush_to_ldisc
|
|
* @work: tty structure passed from work queue.
|
|
*
|
|
* This routine is called out of the software interrupt to flush data
|
|
* from the buffer chain to the line discipline.
|
|
*
|
|
* Locking: holds tty->buf.lock to guard buffer list. Drops the lock
|
|
* while invoking the line discipline receive_buf method. The
|
|
* receive_buf method is single threaded for each tty instance.
|
|
*/
|
|
|
|
static void flush_to_ldisc(struct work_struct *work)
|
|
{
|
|
struct tty_port *port = container_of(work, struct tty_port, buf.work);
|
|
struct tty_bufhead *buf = &port->buf;
|
|
struct tty_struct *tty;
|
|
unsigned long flags;
|
|
struct tty_ldisc *disc;
|
|
|
|
tty = port->itty;
|
|
if (tty == NULL)
|
|
return;
|
|
|
|
disc = tty_ldisc_ref(tty);
|
|
if (disc == NULL)
|
|
return;
|
|
|
|
spin_lock_irqsave(&buf->lock, flags);
|
|
|
|
if (!test_and_set_bit(TTYP_FLUSHING, &port->iflags)) {
|
|
struct tty_buffer *head;
|
|
while ((head = buf->head) != NULL) {
|
|
int count;
|
|
|
|
count = head->commit - head->read;
|
|
if (!count) {
|
|
if (head->next == NULL)
|
|
break;
|
|
buf->head = head->next;
|
|
tty_buffer_free(port, head);
|
|
continue;
|
|
}
|
|
spin_unlock_irqrestore(&buf->lock, flags);
|
|
|
|
count = receive_buf(tty, head, count);
|
|
|
|
spin_lock_irqsave(&buf->lock, flags);
|
|
/* Ldisc or user is trying to flush the buffers.
|
|
We may have a deferred request to flush the
|
|
input buffer, if so pull the chain under the lock
|
|
and empty the queue */
|
|
if (test_bit(TTYP_FLUSHPENDING, &port->iflags)) {
|
|
__tty_buffer_flush(port);
|
|
clear_bit(TTYP_FLUSHPENDING, &port->iflags);
|
|
wake_up(&tty->read_wait);
|
|
break;
|
|
} else if (!count)
|
|
break;
|
|
}
|
|
clear_bit(TTYP_FLUSHING, &port->iflags);
|
|
}
|
|
|
|
spin_unlock_irqrestore(&buf->lock, flags);
|
|
|
|
tty_ldisc_deref(disc);
|
|
}
|
|
|
|
/**
|
|
* tty_flush_to_ldisc
|
|
* @tty: tty to push
|
|
*
|
|
* Push the terminal flip buffers to the line discipline.
|
|
*
|
|
* Must not be called from IRQ context.
|
|
*/
|
|
void tty_flush_to_ldisc(struct tty_struct *tty)
|
|
{
|
|
if (!tty->port->low_latency)
|
|
flush_work(&tty->port->buf.work);
|
|
}
|
|
|
|
/**
|
|
* tty_flip_buffer_push - terminal
|
|
* @port: tty port to push
|
|
*
|
|
* Queue a push of the terminal flip buffers to the line discipline. This
|
|
* function must not be called from IRQ context if port->low_latency is
|
|
* set.
|
|
*
|
|
* In the event of the queue being busy for flipping the work will be
|
|
* held off and retried later.
|
|
*
|
|
* Locking: tty buffer lock. Driver locks in low latency mode.
|
|
*/
|
|
|
|
void tty_flip_buffer_push(struct tty_port *port)
|
|
{
|
|
struct tty_bufhead *buf = &port->buf;
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&buf->lock, flags);
|
|
if (buf->tail != NULL)
|
|
buf->tail->commit = buf->tail->used;
|
|
spin_unlock_irqrestore(&buf->lock, flags);
|
|
|
|
if (port->low_latency)
|
|
flush_to_ldisc(&buf->work);
|
|
else
|
|
schedule_work(&buf->work);
|
|
}
|
|
EXPORT_SYMBOL(tty_flip_buffer_push);
|
|
|
|
/**
|
|
* tty_buffer_init - prepare a tty buffer structure
|
|
* @tty: tty to initialise
|
|
*
|
|
* Set up the initial state of the buffer management for a tty device.
|
|
* Must be called before the other tty buffer functions are used.
|
|
*
|
|
* Locking: none
|
|
*/
|
|
|
|
void tty_buffer_init(struct tty_port *port)
|
|
{
|
|
struct tty_bufhead *buf = &port->buf;
|
|
|
|
spin_lock_init(&buf->lock);
|
|
buf->head = NULL;
|
|
buf->tail = NULL;
|
|
buf->free = NULL;
|
|
buf->memory_used = 0;
|
|
INIT_WORK(&buf->work, flush_to_ldisc);
|
|
}
|
|
|