diff options
| author | Peter Hurley <peter@hurleysoftware.com> | 2013-06-15 09:36:06 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-07-23 16:47:08 -0700 |
| commit | 809850b7a5fcc0a96d023e1171a7944c60fd5a71 (patch) | |
| tree | 5c6a22458a7d756cbfe948bfb6b7d331af01610f /drivers/tty/tty_buffer.c | |
| parent | 2cf7b67e87f0d8db025cff12b5d29c0663bbcd87 (diff) | |
tty: Use lockless flip buffer free list
In preparation for lockless flip buffers, make the flip buffer
free list lockless.
NB: using llist is not the optimal solution, as the driver and
buffer work may contend over the llist head unnecessarily. However,
test measurements indicate this contention is low.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/tty_buffer.c')
| -rw-r--r-- | drivers/tty/tty_buffer.c | 29 |
1 files changed, 12 insertions, 17 deletions
diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c index 0259a766b875..069640e5b9c0 100644 --- 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); } |