[PATCH 4/5] i387: move TS_USEDFPU clearing out of __save_init_fpu and into callers

Linus Torvalds
2012-02-22T20:58:16Z

From: Linus Torvalds <torvalds@linux-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@linux-foundation.org>
Cc: stable@kernel.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