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Date: Sat, 1 Feb 2014 17:35:13 -0800
Message-ID: <CALmL7E_ijZStgyxj4Gnn69sEF-kv+eBE64+J7OBfn-K4cbBmJg@mail.gmail.com>
Subject: Re: [PATCH] Make math_state_restore() save and restore the interrupt flag
From: Suresh Siddha <sbsiddha@gmail.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Nate Eldredge <nate@thatsmathematics.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>,
        "the arch/x86 maintainers" <x86@kernel.org>,
        stable <stable@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Maarten Baert <maarten-baert@hotmail.com>, Jan Kara <jack@suse.cz>,
        George Spelvin <linux@horizon.com>, Pekka Riikonen <priikone@iki.fi>
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Sender: linux-kernel-owner@vger.kernel.org

On Sat, Feb 1, 2014 at 5:26 PM, H. Peter Anvin <hpa@zytor.com> wrote:
> Even "b" does that, no?

oh right. It needs an else. only for non-eager fpu case we should do stts()

  void __kernel_fpu_end(void)
  {
          if (use_eager_fpu()) {
                  struct task_struct *me = current;

                  if (tsk_used_math(me) && likely(!restore_fpu_checking(
me)))
                          return;
          } else
                  stts();
  }

thanks,
suresh

> "a" should be fine as long as we don't ever use
> those features in the kernel, even under kernel_fpu_begin/end().
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