tty: Use lockless flip buffer free list

[firefly-linux-kernel-4.4.55.git] / drivers / tty / tty_buffer.c

diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
index 0259a766b8752cc190f1eec53b49d53a485ef91e..069640e5b9c0eb95fca133525d9beaaf75391770 100644 (file)
--- a/drivers/tty/tty_buffer.c
+++ b/drivers/tty/tty_buffer.c
@@ -44,16 +44,17 @@ static void tty_buffer_reset(struct tty_buffer *p, size_t size)
 void tty_buffer_free_all(struct tty_port *port)
 {
        struct tty_bufhead *buf = &port->buf;
-       struct tty_buffer *p;
+       struct tty_buffer *p, *next;
+       struct llist_node *llist;
 
        while ((p = buf->head) != NULL) {
                buf->head = p->next;
                kfree(p);
        }
-       while ((p = buf->free) != NULL) {
-               buf->free = p->next;
+       llist = llist_del_all(&buf->free);
+       llist_for_each_entry_safe(p, next, llist, free)
                kfree(p);
-       }
+
        buf->tail = NULL;
        buf->memory_used = 0;
 }
@@ -68,22 +69,20 @@ void tty_buffer_free_all(struct tty_port *port)
  *     allocation behaviour.
  *     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 **tbh = &port->buf.free;
+       struct llist_node *free;
        struct tty_buffer *p;
 
        /* Round the buffer size out */
        size = __ALIGN_MASK(size, TTYB_ALIGN_MASK);
 
        if (size <= MIN_TTYB_SIZE) {
-               if (*tbh) {
-                       p = *tbh;
-                       *tbh = p->next;
+               free = llist_del_first(&port->buf.free);
+               if (free) {
+                       p = llist_entry(free, struct tty_buffer, free);
                        goto found;
                }
        }
@@ -109,8 +108,6 @@ found:
  *
  *     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)
@@ -123,10 +120,8 @@ static void tty_buffer_free(struct tty_port *port, struct tty_buffer *b)
 
        if (b->size > MIN_TTYB_SIZE)
                kfree(b);
-       else {
-               b->next = buf->free;
-               buf->free = b;
-       }
+       else
+               llist_add(&b->free, &buf->free);
 }
 
 /**
@@ -542,7 +537,7 @@ void tty_buffer_init(struct tty_port *port)
        spin_lock_init(&buf->lock);
        buf->head = NULL;
        buf->tail = NULL;
-       buf->free = NULL;
+       init_llist_head(&buf->free);
        buf->memory_used = 0;
        INIT_WORK(&buf->work, flush_to_ldisc);
 }