[PATCH 003/208] x86/fpu: Add debugging check to fpu__save()

[Ingo Molnar]

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@xxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 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()) {
-- 
2.1.0

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