evie/android_kernel_oneplus_msm8998
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

x86/fpu: Also check fpu_lazy_restore() when use_eager_fpu()

Browse source 
With Oleg's patch:

  33a3ebdc07 ("x86, fpu: Don't abuse has_fpu in __kernel_fpu_begin/end()")

kernel threads no longer have an FPU state even on systems with
use_eager_fpu().

That in turn means that a task may still have its FPU state
loaded in the FPU registers, if the task only got interrupted by
kernel threads from when it went to sleep, to when it woke up
again.

In that case, there is no need to restore the FPU state for
this task, since it is still in the registers.

The kernel can simply use the same logic to determine this as
is used for !use_eager_fpu() systems.

Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Link: http://lkml.kernel.org/r/1423252925-14451-9-git-send-email-riel@redhat.com
Signed-off-by: Borislav Petkov <bp@suse.de>
This commit is contained in:
Rik van Riel 2015-02-06 15:02:05 -05:00 • committed by Borislav Petkov
parent 6a5fe8952b
commit 728e53fef4
1 changed files with 1 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
arch/x86/include/asm/fpu-internal.h
View file

@ -458,7 +458,7 @@ static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct ta
task_disable_lazy_fpu_restore(old);
if (fpu.preload) {
new->thread.fpu_counter++;
if (!use_eager_fpu() && fpu_lazy_restore(new, cpu))
if (fpu_lazy_restore(new, cpu))
fpu.preload = 0;
else
prefetch(new->thread.fpu.state);