From 069f38b4983efaea92cbe7cc0cacc057af55739a Mon Sep 17 00:00:00 2001
From: Peter Hurley <peter@hurleysoftware.com>
Date: Sun, 12 Jul 2015 20:50:49 -0400
Subject: tty: Replace smp_rmb/smp_wmb with smp_load_acquire/smp_store_release
Clarify flip buffer producer/consumer operation; the use of
smp_load_acquire() and smp_store_release() more clearly indicates
which memory access requires a barrier.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/tty/tty_buffer.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
(limited to 'drivers/tty/tty_buffer.c')
diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
index 4cf263d7dffc..25ba5afbca13 100644
--- a/drivers/tty/tty_buffer.c
+++ b/drivers/tty/tty_buffer.c
@@ -291,12 +291,11 @@ static int __tty_buffer_request_room(struct tty_port *port, size_t size,
n->flags = flags;
buf->tail = n;
b->commit = b->used;
- /* paired w/ barrier in flush_to_ldisc(); ensures the
+ /* paired w/ acquire in flush_to_ldisc(); ensures the
* latest commit value can be read before the head is
* advanced to the next buffer
*/
- smp_wmb();
- b->next = n;
+ smp_store_release(&b->next, n);
} else if (change)
size = 0;
else
@@ -488,12 +487,11 @@ static void flush_to_ldisc(struct work_struct *work)
if (atomic_read(&buf->priority))
break;
- next = head->next;
- /* paired w/ barrier in __tty_buffer_request_room();
+ /* paired w/ release in __tty_buffer_request_room();
* ensures commit value read is not stale if the head
* is advancing to the next buffer
*/
- smp_rmb();
+ next = smp_load_acquire(&head->next);
count = head->commit - head->read;
if (!count) {
if (next == NULL) {
--
cgit v1.2.3-70-g09d2
From af5554f957f8a7e28b9826a9c4ad2a7dedd15a78 Mon Sep 17 00:00:00 2001
From: Peter Hurley <peter@hurleysoftware.com>
Date: Sun, 12 Jul 2015 20:50:50 -0400
Subject: tty: buffers: Move hidden buffer index advance into outer loop
The advance of the 'read' buffer index belongs in the outer
flip buffer consume loop, with the other buffer index arithmetic.
No functional change.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/tty/tty_buffer.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
(limited to 'drivers/tty/tty_buffer.c')
diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
index 25ba5afbca13..5a3fa8913880 100644
--- a/drivers/tty/tty_buffer.c
+++ b/drivers/tty/tty_buffer.c
@@ -444,7 +444,6 @@ receive_buf(struct tty_struct *tty, struct tty_buffer *head, int count)
if (count)
disc->ops->receive_buf(tty, p, f, count);
}
- head->read += count;
return count;
}
@@ -506,6 +505,7 @@ static void flush_to_ldisc(struct work_struct *work)
count = receive_buf(tty, head, count);
if (!count)
break;
+ head->read += count;
}
mutex_unlock(&buf->lock);
--
cgit v1.2.3-70-g09d2