Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751705AbbGMAvD (ORCPT ); Sun, 12 Jul 2015 20:51:03 -0400 Received: from mail-qk0-f172.google.com ([209.85.220.172]:33023 "EHLO mail-qk0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751281AbbGMAvB (ORCPT ); Sun, 12 Jul 2015 20:51:01 -0400 From: Peter Hurley To: Greg Kroah-Hartman Cc: Jiri Slaby , linux-kernel@vger.kernel.org, Peter Hurley Subject: [PATCH 1/2] tty: Replace smp_rmb/smp_wmb with smp_load_acquire/smp_store_release Date: Sun, 12 Jul 2015 20:50:49 -0400 Message-Id: <1436748650-4389-1-git-send-email-peter@hurleysoftware.com> X-Mailer: git-send-email 2.4.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1715 Lines: 51 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 --- drivers/tty/tty_buffer.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c index 4cf263d..25ba5af 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) { -- 2.4.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/