Commit a9241ea5 authored Feb 06, 2015 by Oleg Nesterov Committed by Borislav Petkov Feb 19, 2015

x86/fpu: Don't reset thread.fpu_counter



The "else" branch clears ->fpu_counter as a remnant of the lazy FPU
usage counting:

  e07e23e1 ("[PATCH] non lazy "sleazy" fpu implementation")

However, switch_fpu_prepare() does this now so that else branch is
superfluous.

If we do use_eager_fpu(), then this has no effect. Otherwise, if we
actually wanted to prevent fpu preload after the context switch we would
need to reset it unconditionally, even if __thread_has_fpu().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1423252925-14451-2-git-send-email-riel@redhat.com


Signed-off-by: Borislav Petkov <bp@suse.de>

parent bfa76d49

arch/x86/kernel/i387.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -108,8 +108,7 @@ void unlazy_fpu(struct task_struct *tsk)
		if (__thread_has_fpu(tsk)) {
		__save_init_fpu(tsk);
		__thread_fpu_end(tsk);
		} else
		tsk->thread.fpu_counter = 0;
		}
		preempt_enable();
		}
		EXPORT_SYMBOL(unlazy_fpu);