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Date: Sat, 15 Jun 2013 09:14:17 -0400
From: Peter Hurley <peter@...leysoftware.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
Jiri Slaby <jslaby@...e.cz>,
Peter Hurley <peter@...leysoftware.com>
Subject: [PATCH v4 05/24] n_tty: Line copy to user buffer in canonical mode
Instead of pushing one char per loop, pre-compute the data length
to copy and copy all at once.
Signed-off-by: Peter Hurley <peter@...leysoftware.com>
---
drivers/tty/n_tty.c | 110 ++++++++++++++++++++++++++++++++++++----------------
1 file changed, 77 insertions(+), 33 deletions(-)
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 7fd7774..74dcedd 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -74,6 +74,13 @@
#define ECHO_OP_SET_CANON_COL 0x81
#define ECHO_OP_ERASE_TAB 0x82
+#undef N_TTY_TRACE
+#ifdef N_TTY_TRACE
+# define n_tty_trace(f, args...) trace_printk(f, ##args)
+#else
+# define n_tty_trace(f, args...)
+#endif
+
struct n_tty_data {
unsigned int column;
unsigned long overrun_time;
@@ -1748,58 +1755,95 @@ static int copy_from_read_buf(struct tty_struct *tty,
}
/**
- * canon_copy_to_user - copy read data in canonical mode
+ * canon_copy_from_read_buf - copy read data in canonical mode
* @tty: terminal device
* @b: user data
* @nr: size of data
*
* Helper function for n_tty_read. It is only called when ICANON is on;
- * it copies characters one at a time from the read buffer to the user
- * space buffer.
+ * it copies one line of input up to and including the line-delimiting
+ * character into the user-space buffer.
*
* Called under the atomic_read_lock mutex
*/
-static int canon_copy_to_user(struct tty_struct *tty,
- unsigned char __user **b,
- size_t *nr)
+static int canon_copy_from_read_buf(struct tty_struct *tty,
+ unsigned char __user **b,
+ size_t *nr)
{
struct n_tty_data *ldata = tty->disc_data;
unsigned long flags;
- int eol, c;
+ size_t n, size, more, c;
+ unsigned long eol;
+ int ret, tail, found = 0;
/* N.B. avoid overrun if nr == 0 */
+
raw_spin_lock_irqsave(&ldata->read_lock, flags);
- while (*nr && ldata->read_cnt) {
-
- eol = test_and_clear_bit(ldata->read_tail, ldata->read_flags);
- c = ldata->read_buf[ldata->read_tail];
- ldata->read_tail = (ldata->read_tail+1) & (N_TTY_BUF_SIZE-1);
- ldata->read_cnt--;
- if (eol) {
- /* this test should be redundant:
- * we shouldn't be reading data if
- * canon_data is 0
- */
- if (--ldata->canon_data < 0)
- ldata->canon_data = 0;
- }
+
+ n = min_t(size_t, *nr, ldata->read_cnt);
+ if (!n) {
raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
+ return 0;
+ }
- if (!eol || (c != __DISABLED_CHAR)) {
- if (tty_put_user(tty, c, *b))
- return -EFAULT;
- *b += 1;
- *nr -= 1;
- }
- if (eol) {
- tty_audit_push(tty);
- return 0;
- }
- raw_spin_lock_irqsave(&ldata->read_lock, flags);
+ tail = ldata->read_tail;
+ size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
+
+ n_tty_trace("%s: nr:%zu tail:%d n:%zu size:%zu\n",
+ __func__, *nr, tail, n, size);
+
+ eol = find_next_bit(ldata->read_flags, size, tail);
+ more = n - (size - tail);
+ if (eol == N_TTY_BUF_SIZE && more) {
+ /* scan wrapped without finding set bit */
+ eol = find_next_bit(ldata->read_flags, more, 0);
+ if (eol != more)
+ found = 1;
+ } else if (eol != size)
+ found = 1;
+
+ size = N_TTY_BUF_SIZE - tail;
+ n = (found + eol + size) & (N_TTY_BUF_SIZE - 1);
+ c = n;
+
+ if (found && ldata->read_buf[eol] == __DISABLED_CHAR)
+ n--;
+
+ n_tty_trace("%s: eol:%lu found:%d n:%zu c:%zu size:%zu more:%zu\n",
+ __func__, eol, found, n, c, size, more);
+
+ raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
+
+ if (n > size) {
+ ret = copy_to_user(*b, &ldata->read_buf[tail], size);
+ if (ret)
+ return -EFAULT;
+ ret = copy_to_user(*b + size, ldata->read_buf, n - size);
+ } else
+ ret = copy_to_user(*b, &ldata->read_buf[tail], n);
+
+ if (ret)
+ return -EFAULT;
+ *b += n;
+ *nr -= n;
+
+ raw_spin_lock_irqsave(&ldata->read_lock, flags);
+ ldata->read_tail = (ldata->read_tail + c) & (N_TTY_BUF_SIZE - 1);
+ ldata->read_cnt -= c;
+ if (found) {
+ __clear_bit(eol, ldata->read_flags);
+ /* this test should be redundant:
+ * we shouldn't be reading data if
+ * canon_data is 0
+ */
+ if (--ldata->canon_data < 0)
+ ldata->canon_data = 0;
}
raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
+ if (found)
+ tty_audit_push(tty);
return 0;
}
@@ -1972,7 +2016,7 @@ do_it_again:
}
if (ldata->icanon && !L_EXTPROC(tty)) {
- retval = canon_copy_to_user(tty, &b, &nr);
+ retval = canon_copy_from_read_buf(tty, &b, &nr);
if (retval)
break;
} else {
--
1.8.1.2
--
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