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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.c31
1 files changed, 16 insertions, 15 deletions
diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
index f1d30f6945af..143deb62467d 100644
--- a/drivers/tty/tty_buffer.c
+++ b/drivers/tty/tty_buffer.c
@@ -60,6 +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)
{
@@ -73,6 +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
@@ -255,16 +257,15 @@ static int __tty_buffer_request_room(struct tty_port *port, size_t size,
if (change || left < size) {
/* This is the slow path - looking for new buffers to use */
if ((n = tty_buffer_alloc(port, size)) != NULL) {
- unsigned long iflags;
-
n->flags = flags;
buf->tail = n;
-
- spin_lock_irqsave(&buf->flush_lock, iflags);
b->commit = b->used;
+ /* 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;
- spin_unlock_irqrestore(&buf->flush_lock, iflags);
-
} else if (change)
size = 0;
else
@@ -448,27 +449,28 @@ static void flush_to_ldisc(struct work_struct *work)
mutex_lock(&buf->lock);
while (1) {
- unsigned long flags;
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;
- spin_lock_irqsave(&buf->flush_lock, flags);
+ 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) {
- spin_unlock_irqrestore(&buf->flush_lock, flags);
+ if (next == NULL)
break;
- }
- buf->head = head->next;
- spin_unlock_irqrestore(&buf->flush_lock, flags);
+ buf->head = next;
tty_buffer_free(port, head);
continue;
}
- spin_unlock_irqrestore(&buf->flush_lock, flags);
count = receive_buf(tty, head, count);
if (!count)
@@ -523,7 +525,6 @@ void tty_buffer_init(struct tty_port *port)
struct tty_bufhead *buf = &port->buf;
mutex_init(&buf->lock);
- spin_lock_init(&buf->flush_lock);
tty_buffer_reset(&buf->sentinel, 0);
buf->head = &buf->sentinel;
buf->tail = &buf->sentinel;