linux-kernel - Re: [PATCH] Make math_state_restore() save and restore the interrupt flag

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Date:	Sat, 01 Feb 2014 17:43:57 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Suresh Siddha <sbsiddha@...il.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Nate Eldredge <nate@...tsmathematics.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	stable <stable@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Maarten Baert <maarten-baert@...mail.com>,
	Jan Kara <jack@...e.cz>, George Spelvin <linux@...izon.com>,
	Pekka Riikonen <priikone@....fi>
Subject: Re: [PATCH] Make math_state_restore() save and restore the interrupt flag

What does the inner if clause do? It looks like it returns either way...

On February 1, 2014 5:35:13 PM PST, Suresh Siddha <sbsiddha@...il.com> wrote:
>On Sat, Feb 1, 2014 at 5:26 PM, H. Peter Anvin <hpa@...or.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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