i387: move TS_USEDFPU clearing out of __save_init_fpu and into callers

This change “i387: move TS_USEDFPU clearing out of __save_init_fpu and into callers” (commit b6c6641) in Linux kernel is authored by Linus Torvalds <torvalds [at] linux-foundation.org> on Thu Feb 16 12:22:48 2012 -0800.

Description of "i387: move TS_USEDFPU clearing out of __save_init_fpu and into callers"

The change “i387: move TS_USEDFPU clearing out of __save_init_fpu and into callers” introduces changes as follows.

i387: move TS_USEDFPU clearing out of __save_init_fpu and into callers

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>

Linux kernel releases containing commit b6c6641

The Linux kernel releases containing this commit are as follows.

Linux kernel code changes from "i387: move TS_USEDFPU clearing out of __save_init_fpu and into callers"

There are 9 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 arch/x86/include/asm/i387.h | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)
 
diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h
index f704be239883..1e12c2d087e4 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();
 }

The commit for this change in Linux stable tree is b6c6641 (patch).

Last modified: 2020/02/10