linux-kernel - [PATCH 0/2 v2] minor cleanups to EFLAGS initialisation in ret_from

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Message-ID: <1312993743.26263.268.camel@zakaz.uk.xensource.com>
Date:	Wed, 10 Aug 2011 17:29:03 +0100
From:	Ian Campbell <Ian.Campbell@...rix.com>
To:	<linux-kernel@...r.kernel.org>
CC:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"H. Peter Anvin" <hpa@...or.com>,
	Pekka Enberg <penberg@...nel.org>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Andi Kleen <ak@...ux.intel.com>, Ingo Molnar <mingo@...e.hu>,
	Brian Gerst <brgerst@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"x86@...nel.org" <x86@...nel.org>,
	LinusTorvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 0/2 v2] minor cleanups to EFLAGS initialisation in
 ret_from_fork

The following series removes the use of a global kernel_eflags variable
from the x86_64 ret_from_fork path and (very slightly) merges the 32 and
64 bit version of that code path.

kernel_eflags could be made a __read_mostly but actually there is no
reason to prefer the value at cpu_init() time to a compile time constant
value for the initial eflags after a fork.

Test booted on 32 and 64 bit.

changes since v1:
      * rebased onto tip/master
      * make 32 bit look like 64 bit instead of vice versa since the
        behaviour of resetting eflags with interrupts disabled before
        calling schedule_tail seems more obviously safe than resetting
        eflags with interrupts enabled afterwards (although I think both
        are actually correct).
      * As a consequence of the above patch 3/3 (use symbolic names for
        bits in eflags) goes away since we only use the MBO bit 1 now,
        which doesn't have a name.

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