linux-kernel - [PATCH 4/5] i387: move TS_USEDFPU clearing out of __save_init

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Date:	Wed, 22 Feb 2012 12:58:11 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org
cc:	Raphael Prevost <raphael@...o.asia>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Peter Anvin <hpa@...or.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH 4/5] i387: move TS_USEDFPU clearing out of __save_init_fpu
 and into callers


From: Linus Torvalds <torvalds@...ux-foundation.org>
Date: Thu, 16 Feb 2012 12:22:48 -0800

[ Upstream commit b6c66418dcad0fcf83cd1d0a39482db37bf4fc41 ]

Touching TS_USEDFPU without touching CR0.TS is confusing, so don't do
it.  By moving it into the callers, we always do the TS_USEDFPU next to
the CR0.TS accesses in the source code, and it's much easier to see how
the two go hand in hand.

Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: stable@...nel.org	# Helps backporting
---
 arch/x86/include/asm/i387.h |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h
index 6e87fa43c357..55fb3aa84b0d 100644
--- a/arch/x86/include/asm/i387.h
+++ b/arch/x86/include/asm/i387.h
@@ -259,7 +259,6 @@ static inline void fpu_save_init(struct fpu *fpu)
 static inline void __save_init_fpu(struct task_struct *tsk)
 {
 	fpu_save_init(&tsk->thread.fpu);
-	task_thread_info(tsk)->status &= ~TS_USEDFPU;
 }
 
 static inline int fpu_fxrstor_checking(struct fpu *fpu)
@@ -290,6 +289,7 @@ static inline void __unlazy_fpu(struct task_struct *tsk)
 {
 	if (task_thread_info(tsk)->status & TS_USEDFPU) {
 		__save_init_fpu(tsk);
+		task_thread_info(tsk)->status &= ~TS_USEDFPU;
 		stts();
 	} else
 		tsk->fpu_counter = 0;
@@ -356,9 +356,11 @@ static inline void kernel_fpu_begin(void)
 
 	WARN_ON_ONCE(!irq_fpu_usable());
 	preempt_disable();
-	if (me->status & TS_USEDFPU)
+	if (me->status & TS_USEDFPU) {
 		__save_init_fpu(me->task);
-	else
+		me->status &= ~TS_USEDFPU;
+		/* We do 'stts()' in kernel_fpu_end() */
+	} else
 		clts();
 }
 
@@ -449,6 +451,7 @@ static inline void save_init_fpu(struct task_struct *tsk)
 	WARN_ON_ONCE(!(task_thread_info(tsk)->status & TS_USEDFPU));
 	preempt_disable();
 	__save_init_fpu(tsk);
+	task_thread_info(tsk)->status &= ~TS_USEDFPU;
 	stts();
 	preempt_enable();
 }
-- 
1.7.9.188.g12766.dirty

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