lkml.org 
[lkml]   [2015]   [Jan]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [RFC PATCH 05/11] x86,fpu: ensure FPU state is reloaded from memory if task is traced
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 01/13/2015 11:50 AM, Oleg Nesterov wrote:
> On 01/13, Rik van Riel wrote:
>>
>>>> @@ -412,8 +412,14 @@ static inline void
>>>> switch_fpu_prepare(struct task_struct *old, struct task_struc
>>>> bool preload = tsk_used_math(new) && (use_eager_fpu() ||
>>>> new->thread.fpu_counter
>>>>> 5); if (__thread_has_fpu(old)) { - if
>>>>> (!__save_init_fpu(old))
>>>> + /* + * Make sure the FPU state is restored from memory
>>>> next time, + * if the task has an FPU exception pending, or
>>>> the task's in + * memory FPU state could be changed by a
>>>> debugger. + */ + if (!__save_init_fpu(old) ||
>>>> task_is_stopped_or_traced(old)) cpu = ~0;
>>>
>>> Well, if debugger wants to change FPU state, it should call
>>> init_fpu() which resets .last_cpu ?
>>
>> Does the ptrace (and utrace, and ... ) code actually do that?
>
> Yes, see xfpregs_get/set. So I think this change is not needed (but
> I didn't look at the next patches).

Excellent, I will drop this then.

- --
All rights reversed
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1

iQEcBAEBAgAGBQJUtU6FAAoJEM553pKExN6Dn1YH/0zWFvPtmbSWPez8EfsnHJe9
dF0h0kUHMKb1bUFNyqrQpmX1MuBHba9ab4a1P8ySoC9nIo8F7spSX+OG/CigDZzZ
vguz9J/MFrjhW83+eeyVc5PLwtVWwiYzbGB+Xc8ValMqHPT8m6kG2H+hw6ItRtnR
UwoPeQn27WjdaVT9/L13uYA8i6vwqD6pO68PzBs3xSFXbt0FHl9T0jaZ5O0WIzav
b7bNQ/HFpCZSqjqmc4KxlavBFlC8Ku9rMTYRzWXYtdjwfcn8rDTKpDZz7uBSd+Gl
bwb0u1rYcQnYQrJVmrarMEoySSfYAp6WsTIl7G/zWfJDSmPOYHLdurimoC14vgA=
=fxF+
-----END PGP SIGNATURE-----

\
 
 \ /
  Last update: 2015-01-13 18:01    [W:0.075 / U:0.156 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site