From: Ralf Baechle <ralf@linux-mips.org>
Date: Wed, 13 Dec 2006 08:34:57 +0000 (-0800)
Subject: [PATCH] tty: remove useless memory barrier
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=34f8f0a5e953d3e40c4419e5e5c4b6fd14f7ebf2;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git

[PATCH] tty: remove useless memory barrier

I don't see why there is a memory barrier in copy_from_read_buf() at all.
Even if it was useful spin_unlock_irqrestore implies a barrier.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c
index e96a00fe1389..2bdb0144a22e 100644
--- a/drivers/char/n_tty.c
+++ b/drivers/char/n_tty.c
@@ -1151,7 +1151,6 @@ static int copy_from_read_buf(struct tty_struct *tty,
 	n = min(*nr, n);
 	spin_unlock_irqrestore(&tty->read_lock, flags);
 	if (n) {
-		mb();
 		retval = copy_to_user(*b, &tty->read_buf[tty->read_tail], n);
 		n -= retval;
 		spin_lock_irqsave(&tty->read_lock, flags);