i387: don't ever touch TS_USEDFPU directly, use helper functions

commit 6d59d7a9f5b723a7ac1925c136e93ec83c0c3043 upstream.

This creates three helper functions that do the TS_USEDFPU accesses, and
makes everybody that used to do it by hand use those helpers instead.

In addition, there's a couple of helper functions for the "change both
CR0.TS and TS_USEDFPU at the same time" case, and the places that do
that together have been changed to use those.  That means that we have
fewer random places that open-code this situation.

The intent is partly to clarify the code without actually changing any
semantics yet (since we clearly still have some hard to reproduce bug in
this area), but also to make it much easier to use another approach
entirely to caching the CR0.TS bit for software accesses.

Right now we use a bit in the thread-info 'status' variable (this patch
does not change that), but we might want to make it a full field of its
own or even make it a per-cpu variable.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 727e6c16f294..bb5445c5450d 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -579,7 +579,7 @@ void __math_state_restore(void)
 		return;
 	}
 
-	thread->status |= TS_USEDFPU;	/* So we fnsave on switch_to() */
+	__thread_set_has_fpu(thread);	/* clts in caller! */
 	tsk->fpu_counter++;
 }