Messages in this thread | | | Date | Mon, 2 Feb 2015 20:21:39 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH 4/6] x86,fpu: use disable_task_lazy_fpu_restore helper |
| |
I'll try to read this patch tomorrow. Too late for me.
I think it is fine, but
On 02/02, riel@redhat.com wrote: > > This also fixes the lazy FPU restore disabling in drop_fpu, which > only really works when !use_eager_fpu(). > ... > > --- a/arch/x86/include/asm/fpu-internal.h > +++ b/arch/x86/include/asm/fpu-internal.h > @@ -396,7 +396,7 @@ static inline void drop_fpu(struct task_struct *tsk) > * Forget coprocessor state.. > */ > preempt_disable(); > - tsk->thread.fpu_counter = 0; > + task_disable_lazy_fpu_restore(tsk); > __drop_fpu(tsk); > clear_used_math();
perhaps this makes sense anyway, but I am not sure if the changelog is right.
Note that we clear PF_USED_MATH, last_fpu/has_fpu have no effect after this.
> preempt_enable(); > @@ -440,7 +440,7 @@ static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct ta > new->thread.fpu_counter > 5); > if (__thread_has_fpu(old)) { > if (!__save_init_fpu(old)) > - old->thread.fpu.last_cpu = ~0; > + task_disable_lazy_fpu_restore(old); > else > old->thread.fpu.last_cpu = cpu; > old->thread.fpu.has_fpu = 0; /* But leave fpu_owner_task! */ > @@ -454,7 +454,7 @@ static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct ta > stts(); > } else { > old->thread.fpu_counter = 0; > - old->thread.fpu.last_cpu = ~0; > + task_disable_lazy_fpu_restore(old);
I am also wondering if we can remove this task_disable_lazy_fpu_restore... I mean, perhaps we should shift this into __thread_fpu_end() path. But this is almost off-topic and in any case this patch should not do this.
Oleg.
| |