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Commit 069f38b4 authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
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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: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e5eb517d

drivers/tty/tty_buffer.c

+4 −6
Original line number Diff line number Diff line
@@ -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) {