diff options
| -rw-r--r-- | drivers/tty/n_tty.c | 52 |
1 files changed, 42 insertions, 10 deletions
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index 3a1a79462d16..b89308d52ade 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -1943,19 +1943,17 @@ static inline int input_available_p(struct tty_struct *tty, int poll) * Helper function to speed up n_tty_read. It is only called when * ICANON is off; it copies characters straight from the tty queue. * - * It can be profitably called twice; once to drain the space from - * the tail pointer to the (physical) end of the buffer, and once - * to drain the space from the (physical) beginning of the buffer - * to head pointer. - * * Called under the ldata->atomic_read_lock sem * + * Returns true if it successfully copied data, but there is still + * more data to be had. + * * n_tty_read()/consumer path: * caller holds non-exclusive termios_rwsem * read_tail published */ -static void copy_from_read_buf(struct tty_struct *tty, +static bool copy_from_read_buf(struct tty_struct *tty, unsigned char **kbp, size_t *nr) @@ -1978,10 +1976,14 @@ static void copy_from_read_buf(struct tty_struct *tty, /* Turn single EOF into zero-length read */ if (L_EXTPROC(tty) && ldata->icanon && is_eof && (head == ldata->read_tail)) - n = 0; + return false; *kbp += n; *nr -= n; + + /* If we have more to copy, let the caller know */ + return head != ldata->read_tail; } + return false; } /** @@ -2132,6 +2134,25 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, int packet; size_t tail; + /* + * Is this a continuation of a read started earler? + * + * If so, we still hold the atomic_read_lock and the + * termios_rwsem, and can just continue to copy data. + */ + if (*cookie) { + if (copy_from_read_buf(tty, &kb, &nr)) + return kb - kbuf; + + /* No more data - release locks and stop retries */ + n_tty_kick_worker(tty); + n_tty_check_unthrottle(tty); + up_read(&tty->termios_rwsem); + mutex_unlock(&ldata->atomic_read_lock); + *cookie = NULL; + return kb - kbuf; + } + c = job_control(tty, file); if (c < 0) return c; @@ -2226,9 +2247,20 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, nr--; } - /* See comment above copy_from_read_buf() why twice */ - copy_from_read_buf(tty, &kb, &nr); - copy_from_read_buf(tty, &kb, &nr); + /* + * Copy data, and if there is more to be had + * and we have nothing more to wait for, then + * let's mark us for retries. + * + * NOTE! We return here with both the termios_sem + * and atomic_read_lock still held, the retries + * will release them when done. + */ + if (copy_from_read_buf(tty, &kb, &nr) && kb - kbuf >= minimum) { + remove_wait_queue(&tty->read_wait, &wait); + *cookie = cookie; + return kb - kbuf; + } } n_tty_check_unthrottle(tty); |