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path: root/drivers/tty/n_tty.c
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Diffstat (limited to 'drivers/tty/n_tty.c')
-rw-r--r--drivers/tty/n_tty.c52
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);