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x86/fpu: Introduce task_disable_lazy_fpu_restore() helper

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Currently there are a few magic assignments sprinkled through the
code that disable lazy FPU state restoring, some more effective than
others, and all equally mystifying.

It would be easier to have a helper to explicitly disable lazy
FPU state restoring for a task.

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/1423252925-14451-6-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 15:02:02 -05:00 committed by Borislav Petkov
parent 1c927eea4c
commit 33e03dedd7
1 changed files with 10 additions and 0 deletions
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10
arch/x86/include/asm/fpu-internal.h
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@ -79,6 +79,16 @@ static inline void __cpu_disable_lazy_restore(unsigned int cpu)
per_cpu(fpu_owner_task, cpu) = NULL; per_cpu(fpu_owner_task, cpu) = NULL;
} }
/*
* Used to indicate that the FPU state in memory is newer than the FPU
* state in registers, and the FPU state should be reloaded next time the
* task is run. Only safe on the current task, or non-running tasks.
*/
static inline void task_disable_lazy_fpu_restore(struct task_struct *tsk)
{
tsk->thread.fpu.last_cpu = ~0;
}
static inline int fpu_lazy_restore(struct task_struct *new, unsigned int cpu) static inline int fpu_lazy_restore(struct task_struct *new, unsigned int cpu)
{ {
return new == this_cpu_read_stable(fpu_owner_task) && return new == this_cpu_read_stable(fpu_owner_task) &&