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path: root/drivers/tty/tty_buffer.c
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Diffstat (limited to 'drivers/tty/tty_buffer.c')
-rw-r--r--drivers/tty/tty_buffer.c85
1 files changed, 55 insertions, 30 deletions
diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
index 08835a6dd02..143deb62467 100644
--- a/drivers/tty/tty_buffer.c
+++ b/drivers/tty/tty_buffer.c
@@ -11,7 +11,6 @@
#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>
@@ -61,6 +60,7 @@ void tty_buffer_lock_exclusive(struct tty_port *port)
atomic_inc(&buf->priority);
mutex_lock(&buf->lock);
}
+EXPORT_SYMBOL_GPL(tty_buffer_lock_exclusive);
void tty_buffer_unlock_exclusive(struct tty_port *port)
{
@@ -74,6 +74,7 @@ void tty_buffer_unlock_exclusive(struct tty_port *port)
if (restart)
queue_work(system_unbound_wq, &buf->work);
}
+EXPORT_SYMBOL_GPL(tty_buffer_unlock_exclusive);
/**
* tty_buffer_space_avail - return unused buffer space
@@ -101,6 +102,7 @@ static void tty_buffer_reset(struct tty_buffer *p, size_t size)
p->next = NULL;
p->commit = 0;
p->read = 0;
+ p->flags = 0;
}
/**
@@ -229,31 +231,53 @@ void tty_buffer_flush(struct tty_struct *tty)
* tty_buffer_request_room - grow tty buffer if needed
* @tty: tty structure
* @size: size desired
+ * @flags: buffer flags if new buffer allocated (default = 0)
*
* Make at least size bytes of linear space available for the tty
* buffer. If we fail return the size we managed to find.
+ *
+ * Will change over to a new buffer if the current buffer is encoded as
+ * TTY_NORMAL (so has no flags buffer) and the new buffer requires
+ * a flags buffer.
*/
-int tty_buffer_request_room(struct tty_port *port, size_t size)
+static int __tty_buffer_request_room(struct tty_port *port, size_t size,
+ int flags)
{
struct tty_bufhead *buf = &port->buf;
struct tty_buffer *b, *n;
- int left;
+ int left, change;
b = buf->tail;
- left = b->size - b->used;
+ if (b->flags & TTYB_NORMAL)
+ left = 2 * b->size - b->used;
+ else
+ left = b->size - b->used;
- if (left < size) {
+ change = (b->flags & TTYB_NORMAL) && (~flags & TTYB_NORMAL);
+ if (change || left < size) {
/* This is the slow path - looking for new buffers to use */
if ((n = tty_buffer_alloc(port, size)) != NULL) {
+ n->flags = flags;
buf->tail = n;
b->commit = b->used;
- smp_mb();
+ /* paired w/ barrier in flush_to_ldisc(); ensures the
+ * latest commit value can be read before the head is
+ * advanced to the next buffer
+ */
+ smp_wmb();
b->next = n;
- } else
+ } else if (change)
+ size = 0;
+ else
size = left;
}
return size;
}
+
+int tty_buffer_request_room(struct tty_port *port, size_t size)
+{
+ return __tty_buffer_request_room(port, size, 0);
+}
EXPORT_SYMBOL_GPL(tty_buffer_request_room);
/**
@@ -273,12 +297,14 @@ int tty_insert_flip_string_fixed_flag(struct tty_port *port,
int copied = 0;
do {
int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
- int space = tty_buffer_request_room(port, goal);
+ int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0;
+ int space = __tty_buffer_request_room(port, goal, flags);
struct tty_buffer *tb = port->buf.tail;
if (unlikely(space == 0))
break;
memcpy(char_buf_ptr(tb, tb->used), chars, space);
- memset(flag_buf_ptr(tb, tb->used), flag, space);
+ if (~tb->flags & TTYB_NORMAL)
+ memset(flag_buf_ptr(tb, tb->used), flag, space);
tb->used += space;
copied += space;
chars += space;
@@ -331,14 +357,11 @@ EXPORT_SYMBOL(tty_insert_flip_string_flags);
* 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.
*/
void tty_schedule_flip(struct tty_port *port)
{
struct tty_bufhead *buf = &port->buf;
- WARN_ON(port->low_latency);
buf->tail->commit = buf->tail->used;
schedule_work(&buf->work);
@@ -361,11 +384,12 @@ EXPORT_SYMBOL(tty_schedule_flip);
int tty_prepare_flip_string(struct tty_port *port, unsigned char **chars,
size_t size)
{
- int space = tty_buffer_request_room(port, size);
+ int space = __tty_buffer_request_room(port, size, TTYB_NORMAL);
if (likely(space)) {
struct tty_buffer *tb = port->buf.tail;
*chars = char_buf_ptr(tb, tb->used);
- memset(flag_buf_ptr(tb, tb->used), TTY_NORMAL, space);
+ if (~tb->flags & TTYB_NORMAL)
+ memset(flag_buf_ptr(tb, tb->used), TTY_NORMAL, space);
tb->used += space;
}
return space;
@@ -378,7 +402,10 @@ receive_buf(struct tty_struct *tty, struct tty_buffer *head, int count)
{
struct tty_ldisc *disc = tty->ldisc;
unsigned char *p = char_buf_ptr(head, head->read);
- char *f = flag_buf_ptr(head, head->read);
+ char *f = NULL;
+
+ if (~head->flags & TTYB_NORMAL)
+ f = flag_buf_ptr(head, head->read);
if (disc->ops->receive_buf2)
count = disc->ops->receive_buf2(tty, p, f, count);
@@ -423,17 +450,24 @@ static void flush_to_ldisc(struct work_struct *work)
while (1) {
struct tty_buffer *head = buf->head;
+ struct tty_buffer *next;
int count;
/* Ldisc or user is trying to gain exclusive access */
if (atomic_read(&buf->priority))
break;
+ next = head->next;
+ /* paired w/ barrier in __tty_buffer_request_room();
+ * ensures commit value read is not stale if the head
+ * is advancing to the next buffer
+ */
+ smp_rmb();
count = head->commit - head->read;
if (!count) {
- if (head->next == NULL)
+ if (next == NULL)
break;
- buf->head = head->next;
+ buf->head = next;
tty_buffer_free(port, head);
continue;
}
@@ -458,17 +492,15 @@ static void flush_to_ldisc(struct work_struct *work)
*/
void tty_flush_to_ldisc(struct tty_struct *tty)
{
- if (!tty->port->low_latency)
- flush_work(&tty->port->buf.work);
+ 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.
+ * Queue a push of the terminal flip buffers to the line discipline.
+ * Can be called from IRQ/atomic context.
*
* In the event of the queue being busy for flipping the work will be
* held off and retried later.
@@ -476,14 +508,7 @@ void tty_flush_to_ldisc(struct tty_struct *tty)
void tty_flip_buffer_push(struct tty_port *port)
{
- struct tty_bufhead *buf = &port->buf;
-
- buf->tail->commit = buf->tail->used;
-
- if (port->low_latency)
- flush_to_ldisc(&buf->work);
- else
- schedule_work(&buf->work);
+ tty_schedule_flip(port);
}
EXPORT_SYMBOL(tty_flip_buffer_push);
generated by cgit v1.2.3-70-g09d2 (git 2.46.0) at 2025-12-08 07:54:38 +0000