lkml.org 
[lkml]   [2015]   [Feb]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 3/8] x86, fpu: kill save_init_fpu(), change math_error() to use unlazy_fpu()
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 02/16/2015 04:09 PM, Borislav Petkov wrote:
> On Fri, Feb 06, 2015 at 03:02:00PM -0500, riel@redhat.com wrote:
>> From: Oleg Nesterov <oleg@redhat.com>

>> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
>> index fb4cb6adf225..51c465846f06 100644 ---
>> a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -663,7
>> +663,7 @@ static void math_error(struct pt_regs *regs, int
>> error_code, int trapnr) /* * Save the info for the exception
>> handler and clear the error. */ - save_init_fpu(task); +
>> unlazy_fpu(task);
>
> Do I see it correctly that even with this there's a not-so-small
> hole *after* conditional_sti() and *before* unlazy_fpu() where
> caller can still get preempted?

That's ok, the context switch will save the register contents
to memory in that case. At that point unlazy_fpu will potentially
do nothing, and the task will process the FPU context that was
saved to memory previously.

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

iQEcBAEBAgAGBQJU4mGKAAoJEM553pKExN6DHoAH/1R3Pak5bZrvnCEBd3lp9/uD
bqtms5VjiWNNhlG0Hpob0eS71p8fO9La8+hPwFQJdK9yZ2lwvrDEXMCMGOG1P8by
HHbtxS74tUIm49qlIIUNxoiI+HMDnOQNhYv9dA4VdTMcY//2Asr6g4LM3wFH+f1q
tZJ5CU5/f0g2SCtTEzXxZDQdlqgpGXpvcGVymENe45uzn5ZYgcbCAiix+Dy5SiCw
+GjURoRW07iRSvK48w8vTVstTwl2WKgHpWEGVGhL1RyJY6aMIft3b4FH1jUrhVVJ
w3ncQAptA2ry/anU/6A2aTrZ646ebJuYejhF99gwTucolJ3netdX7xohOaFEpSc=
=/rU9
-----END PGP SIGNATURE-----


\
 
 \ /
  Last update: 2015-02-16 22:41    [W:0.079 / U:0.016 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site