From f4c3686386393c120710dd34df2a74183ab805fd Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Fri, 13 Mar 2015 09:53:10 +0100 Subject: [PATCH] x86/fpu: Drop_fpu() should not assume that tsk equals current drop_fpu() does clear_used_math() and usually this is correct because tsk == current. However switch_fpu_finish()->restore_fpu_checking() is called before __switch_to() updates the "current_task" variable. If it fails, we will wrongly clear the PF_USED_MATH flag of the previous task. So use clear_stopped_child_used_math() instead. Signed-off-by: Oleg Nesterov Signed-off-by: Borislav Petkov Reviewed-by: Rik van Riel Cc: Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Dave Hansen Cc: Fenghua Yu Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Pekka Riikonen Cc: Quentin Casasnovas Cc: Suresh Siddha Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20150309171041.GB11388@redhat.com Signed-off-by: Ingo Molnar --- arch/x86/include/asm/fpu-internal.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h index 0dbc08282291..72ba21a8b5fc 100644 --- a/arch/x86/include/asm/fpu-internal.h +++ b/arch/x86/include/asm/fpu-internal.h @@ -370,7 +370,7 @@ static inline void drop_fpu(struct task_struct *tsk) preempt_disable(); tsk->thread.fpu_counter = 0; __drop_fpu(tsk); - clear_used_math(); + clear_stopped_child_used_math(tsk); preempt_enable(); } -- 2.20.1