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Diffstat (limited to 'kernel/drivers/tty/tty_buffer.c')
-rw-r--r--kernel/drivers/tty/tty_buffer.c51
1 files changed, 36 insertions, 15 deletions
diff --git a/kernel/drivers/tty/tty_buffer.c b/kernel/drivers/tty/tty_buffer.c
index 2f78b77f0..3cd31e0d4 100644
--- a/kernel/drivers/tty/tty_buffer.c
+++ b/kernel/drivers/tty/tty_buffer.c
@@ -242,7 +242,10 @@ void tty_buffer_flush(struct tty_struct *tty, struct tty_ldisc *ld)
atomic_inc(&buf->priority);
mutex_lock(&buf->lock);
- while ((next = buf->head->next) != NULL) {
+ /* paired w/ release in __tty_buffer_request_room; ensures there are
+ * no pending memory accesses to the freed buffer
+ */
+ while ((next = smp_load_acquire(&buf->head->next)) != NULL) {
tty_buffer_free(port, buf->head);
buf->head = next;
}
@@ -286,16 +289,19 @@ static int __tty_buffer_request_room(struct tty_port *port, size_t 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 = tty_buffer_alloc(port, size);
+ if (n != NULL) {
n->flags = flags;
buf->tail = n;
- b->commit = b->used;
- /* paired w/ barrier in flush_to_ldisc(); ensures the
+ /* paired w/ acquire in flush_to_ldisc(); ensures
+ * flush_to_ldisc() sees buffer data.
+ */
+ smp_store_release(&b->commit, b->used);
+ /* paired w/ acquire 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;
+ smp_store_release(&b->next, n);
} else if (change)
size = 0;
else
@@ -393,8 +399,11 @@ void tty_schedule_flip(struct tty_port *port)
{
struct tty_bufhead *buf = &port->buf;
- buf->tail->commit = buf->tail->used;
- schedule_work(&buf->work);
+ /* paired w/ acquire in flush_to_ldisc(); ensures
+ * flush_to_ldisc() sees buffer data.
+ */
+ smp_store_release(&buf->tail->commit, buf->tail->used);
+ queue_work(system_unbound_wq, &buf->work);
}
EXPORT_SYMBOL(tty_schedule_flip);
@@ -441,10 +450,9 @@ receive_buf(struct tty_struct *tty, struct tty_buffer *head, int count)
count = disc->ops->receive_buf2(tty, p, f, count);
else {
count = min_t(int, count, tty->receive_room);
- if (count)
+ if (count && disc->ops->receive_buf)
disc->ops->receive_buf(tty, p, f, count);
}
- head->read += count;
return count;
}
@@ -468,7 +476,7 @@ static void flush_to_ldisc(struct work_struct *work)
struct tty_struct *tty;
struct tty_ldisc *disc;
- tty = port->itty;
+ tty = READ_ONCE(port->itty);
if (tty == NULL)
return;
@@ -487,13 +495,15 @@ static void flush_to_ldisc(struct work_struct *work)
if (atomic_read(&buf->priority))
break;
- next = head->next;
- /* paired w/ barrier in __tty_buffer_request_room();
+ /* paired w/ release 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;
+ next = smp_load_acquire(&head->next);
+ /* paired w/ release in __tty_buffer_request_room() or in
+ * tty_buffer_flush(); ensures we see the committed buffer data
+ */
+ count = smp_load_acquire(&head->commit) - head->read;
if (!count) {
if (next == NULL) {
check_other_closed(tty);
@@ -507,6 +517,7 @@ static void flush_to_ldisc(struct work_struct *work)
count = receive_buf(tty, head, count);
if (!count)
break;
+ head->read += count;
}
mutex_unlock(&buf->lock);
@@ -576,3 +587,13 @@ void tty_buffer_set_lock_subclass(struct tty_port *port)
{
lockdep_set_subclass(&port->buf.lock, TTY_LOCK_SLAVE);
}
+
+bool tty_buffer_restart_work(struct tty_port *port)
+{
+ return queue_work(system_unbound_wq, &port->buf.work);
+}
+
+bool tty_buffer_cancel_work(struct tty_port *port)
+{
+ return cancel_work_sync(&port->buf.work);
+}