linux-kernel - [PATCH 3/3] x86,fpu: use disable_task_lazy_fpu

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Date:	Fri, 30 Jan 2015 12:49:30 -0500
From:	riel@...hat.com
To:	oleg@...hat.com
Cc:	dave.hansen@...ux.intel.com, sbsiddha@...il.com,
	luto@...capital.net, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, fenghua.yu@...el.com, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] x86,fpu: use disable_task_lazy_fpu_restore helper

From: Rik van Riel <riel@...hat.com>

Replace magic assignments of fpu.last_cpu = ~0 with more explicit
disable_task_lazy_fpu_restore calls.

This also fixes the lazy FPU restore disabling in drop_fpu, which
only really works when !use_eager_fpu().  This is fine for now,
because fpu_lazy_restore() is only used when !use_eager_fpu()
currently, but we may want to expand that.

Signed-off-by: Rik van Riel <riel@...hat.com>
---
 arch/x86/include/asm/fpu-internal.h | 9 +++++----
 arch/x86/kernel/i387.c              | 2 +-
 arch/x86/kernel/process.c           | 2 +-
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h
index c1f66261ad12..e2832f9dfed5 100644
--- a/arch/x86/include/asm/fpu-internal.h
+++ b/arch/x86/include/asm/fpu-internal.h
@@ -396,7 +396,7 @@ static inline void drop_fpu(struct task_struct *tsk)
 	 * Forget coprocessor state..
 	 */
 	preempt_disable();
-	tsk->thread.fpu_counter = 0;
+	task_disable_lazy_fpu_restore(tsk);
 	__drop_fpu(tsk);
 	clear_used_math();
 	preempt_enable();
@@ -440,8 +440,9 @@ static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct ta
 					     new->thread.fpu_counter > 5);
 	if (__thread_has_fpu(old)) {
 		if (!__save_init_fpu(old))
-			cpu = ~0;
-		old->thread.fpu.last_cpu = cpu;
+			task_disable_lazy_fpu_restore(old);
+		else
+			old->thread.fpu.last_cpu = cpu;
 		old->thread.fpu.has_fpu = 0;	/* But leave fpu_owner_task! */
 
 		/* Don't change CR0.TS if we just switch! */
@@ -453,7 +454,7 @@ static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct ta
 			stts();
 	} else {
 		old->thread.fpu_counter = 0;
-		old->thread.fpu.last_cpu = ~0;
+		task_disable_lazy_fpu_restore(old);
 		if (fpu.preload) {
 			new->thread.fpu_counter++;
 			if (!use_eager_fpu() && fpu_lazy_restore(new, cpu))
diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index 8e070a6c30e5..8416b5f85806 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -250,7 +250,7 @@ int init_fpu(struct task_struct *tsk)
 	if (tsk_used_math(tsk)) {
 		if (cpu_has_fpu && tsk == current)
 			unlazy_fpu(tsk);
-		tsk->thread.fpu.last_cpu = ~0;
+		task_disable_lazy_fpu_restore(tsk);
 		return 0;
 	}
 
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index dd9a069a5ec5..83480373a642 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -68,8 +68,8 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 
 	dst->thread.fpu_counter = 0;
 	dst->thread.fpu.has_fpu = 0;
-	dst->thread.fpu.last_cpu = ~0;
 	dst->thread.fpu.state = NULL;
+	task_disable_lazy_fpu_restore(dst);
 	if (tsk_used_math(src)) {
 		int err = fpu_alloc(&dst->thread.fpu);
 		if (err)
-- 
1.9.3

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