[PATCH tip/x86/fpu 5/6] x86/fpu: fpu__drop: check TIF_NEED_FPU_LOAD instead of PF_KTHREAD|PF_USER_WORKER

[Oleg Nesterov]

PF_KTHREAD|PF_USER_WORKER tasks should never clear TIF_NEED_FPU_LOAD,
so the TIF_NEED_FPU_LOAD check should equally filter them out.

And this way an exiting userspace task can avoid the unnecessary "fwait"
if it does context_switch() at least once on its way to exit_thread().

Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
---
 arch/x86/kernel/fpu/core.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 8d674435f173..fa131299c7da 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -693,8 +693,7 @@ void fpu__drop(struct task_struct *tsk)
 {
 	struct fpu *fpu;
 
-	/* PF_KTHREAD tasks do not use the FPU context area: */
-	if (tsk->flags & (PF_KTHREAD | PF_USER_WORKER))
+	if (test_tsk_thread_flag(tsk, TIF_NEED_FPU_LOAD))
 		return;
 
 	fpu = x86_task_fpu(tsk);
-- 
2.25.1.362.g51ebf55