linux-kernel - Re: [PATCH 6/8] x86,fpu: use an explicit if/else in switch_fpu

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Date:	Tue, 17 Feb 2015 09:44:06 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	riel@...hat.com
Cc:	oleg@...hat.com, dave.hansen@...ux.intel.com, sbsiddha@...il.com,
	luto@...capital.net, tglx@...utronix.de, mingo@...nel.org,
	hpa@...or.com, fenghua.yu@...el.com, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/8] x86,fpu: use an explicit if/else in
 switch_fpu_prepare

On Fri, Feb 06, 2015 at 03:02:03PM -0500, riel@...hat.com wrote:
> From: Rik van Riel <riel@...hat.com>
> 
> Use an explicit if/else branch after __save_init_fpu(old) in
> switch_fpu_prepare.  This makes substituting the assignment
> with a call to task_disable_lazy_fpu() in the next patch easier
> to review.
> 
> Signed-off-by: Rik van Riel <riel@...hat.com>

I did space-out stuff a bit ontop, it looks much more readable to me
this way and that fpu.preload assignment is actually parseable at a
quick glance now :-)

---
From: Rik van Riel <riel@...hat.com>
Subject: [PATCH] x86, fpu: Use an explicit if/else in switch_fpu_prepare

Use an explicit if/else branch after __save_init_fpu(old) in
switch_fpu_prepare. This makes substituting the assignment with a call
in task_disable_lazy_fpu_restore() in the next patch easier to review.

Signed-off-by: Rik van Riel <riel@...hat.com>
Link: http://lkml.kernel.org/r/1423252925-14451-7-git-send-email-riel@redhat.com
[ Boris: space out stuff for more readability. ]
Signed-off-by: Borislav Petkov <bp@...e.de>
---
 arch/x86/include/asm/fpu-internal.h | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h
index 9c27f44e1c5c..04c2807aab66 100644
--- a/arch/x86/include/asm/fpu-internal.h
+++ b/arch/x86/include/asm/fpu-internal.h
@@ -434,13 +434,17 @@ static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct ta
 	 * If the task has used the math, pre-load the FPU on xsave processors
 	 * or if the past 5 consecutive context-switches used math.
 	 */
-	fpu.preload = tsk_used_math(new) && (use_eager_fpu() ||
-					     new->thread.fpu_counter > 5);
+	fpu.preload = tsk_used_math(new) &&
+		      (use_eager_fpu() || new->thread.fpu_counter > 5);
+
 	if (__thread_has_fpu(old)) {
 		if (!__save_init_fpu(old))
-			cpu = ~0;
-		old->thread.fpu.last_cpu = cpu;
-		old->thread.fpu.has_fpu = 0;	/* But leave fpu_owner_task! */
+			old->thread.fpu.last_cpu = ~0;
+		else
+			old->thread.fpu.last_cpu = cpu;
+
+		/* But leave fpu_owner_task! */
+		old->thread.fpu.has_fpu = 0;
 
 		/* Don't change CR0.TS if we just switch! */
 		if (fpu.preload) {
-- 
2.2.0.33.gc18b867

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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