linux-kernel - [PATCH] n_tty: Remove reader wakeups for TTY_BREAK/TTY

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Message-Id: <1444823547-8064-1-git-send-email-peter@hurleysoftware.com>
Date:	Wed, 14 Oct 2015 07:52:27 -0400
From:	Peter Hurley <peter@...leysoftware.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Jiri Slaby <jslaby@...e.cz>, linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org,
	Peter Hurley <peter@...leysoftware.com>
Subject: [PATCH] n_tty: Remove reader wakeups for TTY_BREAK/TTY_PARITY chars

Waking the reader immediately upon receipt of TTY_BREAK or TTY_PARITY
chars has no effect on the outcome of read():
1. Only non-canonical/EXTPROC mode applies since canonical mode
   will not return data until a line termination is received anyway
2. EXTPROC mode - the reader will always be woken by the input worker
3. Non-canonical modes
   a. MIN == 0, TIME == 0
   b. MIN == 0, TIME > 0
   c. MIN > 0, TIME > 0
      minimum_to_wake is always 1 in these modes so the reader will always
      be woken by the input worker
   d. MIN > 0, TIME == 0
      although the reader will not be woken by the input worker unless the
      minimum data is received, the reader would not otherwise have
      returned the received data

Signed-off-by: Peter Hurley <peter@...leysoftware.com>
---
 drivers/tty/n_tty.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index bd383c4..53ba0d6 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -1180,8 +1180,6 @@ static void n_tty_receive_break(struct tty_struct *tty)
 		put_tty_queue('\0', ldata);
 	}
 	put_tty_queue('\0', ldata);
-	if (waitqueue_active(&tty->read_wait))
-		wake_up_interruptible_poll(&tty->read_wait, POLLIN);
 }
 
 /**
@@ -1238,8 +1236,6 @@ static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c)
 			put_tty_queue('\0', ldata);
 	} else
 		put_tty_queue(c, ldata);
-	if (waitqueue_active(&tty->read_wait))
-		wake_up_interruptible_poll(&tty->read_wait, POLLIN);
 }
 
 static void
-- 
2.6.1

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