From 87cdb98affe54b6f390f4622b254569b90820817 Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@kernel.org>
Date: Fri, 3 Apr 2015 11:06:43 +0200
Subject: [PATCH] x86/fpu: Add debugging check to fpu__save()

Document the function a bit more and add debugging check that we are only
running this with the current task.

Reviewed-by: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/kernel/i387.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index ac47278cde71..66f1053ae2cd 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -119,9 +119,13 @@ EXPORT_SYMBOL(__kernel_fpu_end);
 
 /*
  * Save the FPU state (initialize it if necessary):
+ *
+ * This only ever gets called for the current task.
  */
 void fpu__save(struct task_struct *tsk)
 {
+	WARN_ON(tsk != current);
+
 	preempt_disable();
 	if (__thread_has_fpu(tsk)) {
 		if (use_eager_fpu()) {
-- 
2.20.1