linux-kernel - [PATCH 4/4] hvc_console: comment mb and make it an smp

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Date:	Thu, 08 Jan 2009 06:14:18 -0600
From:	Milton Miller <miltonm@....com>
To:	Christian Borntraeger <borntraeger@...ibm.com>,
	Benjiman Herrenschmidt <benh@...nel.crashing.org>
cc:	linuxppc-dev list <linuxppc-dev@...abs.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: [PATCH 4/4] hvc_console: comment mb and make it an smp_ one

I remember some history on this barrier.  There was a race between
open via /dev/console and the tty being fully setup.  Its also why
there is a temporary variable and the global is assigned at the end
of the function.

Signed-off-by: Milton Miller <miltonm@....com>


Index: work.git/drivers/char/hvc_console.c
===================================================================
--- work.git.orig/drivers/char/hvc_console.c	2009-01-08 04:33:39.000000000 -0600
+++ work.git/drivers/char/hvc_console.c	2009-01-08 04:35:09.000000000 -0600
@@ -875,8 +875,11 @@ static int hvc_init(void)
 		goto stop_thread;
 	}
 
-	/* FIXME: This mb() seems completely random.  Remove it. */
-	mb();
+	/*
+	 * Make sure tty is fully registered before allowing it to be
+	 * found by hvc_console_device.
+	 */
+	smp_mb();
 	hvc_driver = drv;
 	return 0;
 
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