Commit 016a2e6f authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Ingo Molnar
Browse files

x86/fpu: Check TIF_NEED_FPU_LOAD instead of PF_KTHREAD|PF_USER_WORKER in fpu__drop() 



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: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Cc: Chang S . Bae <chang.seok.bae@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250503143856.GA9009@redhat.com
parent 2d299e3d

arch/x86/kernel/fpu/core.c

+1 −2
Original line number Diff line number Diff line
@@ -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);