diff options
Diffstat (limited to 'drivers/tty/tty_buffer.c')
| -rw-r--r-- | drivers/tty/tty_buffer.c | 59 |
1 files changed, 50 insertions, 9 deletions
diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c index 595d8b49c745..9fdecc795b6b 100644 --- a/drivers/tty/tty_buffer.c +++ b/drivers/tty/tty_buffer.c @@ -5,6 +5,7 @@ #include <linux/types.h> #include <linux/errno.h> +#include <linux/minmax.h> #include <linux/tty.h> #include <linux/tty_driver.h> #include <linux/tty_flip.h> @@ -104,6 +105,7 @@ static void tty_buffer_reset(struct tty_buffer *p, size_t size) p->size = size; p->next = NULL; p->commit = 0; + p->lookahead = 0; p->read = 0; p->flags = 0; } @@ -234,6 +236,7 @@ void tty_buffer_flush(struct tty_struct *tty, struct tty_ldisc *ld) buf->head = next; } buf->head->read = buf->head->commit; + buf->head->lookahead = buf->head->read; if (ld && ld->ops->flush_buffer) ld->ops->flush_buffer(tty); @@ -276,13 +279,15 @@ static int __tty_buffer_request_room(struct tty_port *port, size_t size, if (n != NULL) { n->flags = flags; buf->tail = n; - /* paired w/ acquire in flush_to_ldisc(); ensures - * flush_to_ldisc() sees buffer data. + /* + * Paired w/ acquire in flush_to_ldisc() and lookahead_bufs() + * ensures they see all 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 + /* + * Paired w/ acquire in flush_to_ldisc() and lookahead_bufs() + * ensures the latest commit value can be read before the head + * is advanced to the next buffer. */ smp_store_release(&b->next, n); } else if (change) @@ -459,6 +464,40 @@ int tty_ldisc_receive_buf(struct tty_ldisc *ld, const unsigned char *p, } EXPORT_SYMBOL_GPL(tty_ldisc_receive_buf); +static void lookahead_bufs(struct tty_port *port, struct tty_buffer *head) +{ + head->lookahead = max(head->lookahead, head->read); + + while (head) { + struct tty_buffer *next; + unsigned char *p, *f = NULL; + unsigned int count; + + /* + * Paired w/ release in __tty_buffer_request_room(); + * ensures commit value read is not stale if the head + * is advancing to the next buffer. + */ + 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->lookahead; + if (!count) { + head = next; + continue; + } + + p = char_buf_ptr(head, head->lookahead); + if (~head->flags & TTYB_NORMAL) + f = flag_buf_ptr(head, head->lookahead); + + port->client_ops->lookahead_buf(port, p, f, count); + head->lookahead += count; + } +} + static int receive_buf(struct tty_port *port, struct tty_buffer *head, int count) { @@ -496,7 +535,7 @@ static void flush_to_ldisc(struct work_struct *work) while (1) { struct tty_buffer *head = buf->head; struct tty_buffer *next; - int count; + int count, rcvd; /* Ldisc or user is trying to gain exclusive access */ if (atomic_read(&buf->priority)) @@ -519,10 +558,12 @@ static void flush_to_ldisc(struct work_struct *work) continue; } - count = receive_buf(port, head, count); - if (!count) + rcvd = receive_buf(port, head, count); + head->read += rcvd; + if (rcvd < count) + lookahead_bufs(port, head); + if (!rcvd) break; - head->read += count; if (need_resched()) cond_resched(); |