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x86/fpu: Remove task_disable_lazy_fpu_restore()

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Replace task_disable_lazy_fpu_restore() with easier to read
open-coded uses: we already update the fpu->last_cpu field
explicitly in other cases.

(This also removes yet another task_struct using FPU method.)

Better explain the fpu::last_cpu field in the structure definition.

Reviewed-by: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ingo Molnar 2015-04-23 17:08:41 +02:00
parent ca6787ba0f
commit eb6a3251bf
3 changed files with 15 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
arch/x86/include/asm/fpu-internal.h
View File

@ -74,16 +74,6 @@ static inline void __cpu_disable_lazy_restore(unsigned int cpu)
per_cpu(fpu_fpregs_owner_ctx, 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)
{
return &new->thread.fpu == this_cpu_read_stable(fpu_fpregs_owner_ctx) &&
@ -430,7 +420,7 @@ static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct ta
if (old_fpu->has_fpu) {
if (!fpu_save_init(&old->thread.fpu))
task_disable_lazy_fpu_restore(old);
old->thread.fpu.last_cpu = -1;
else
old->thread.fpu.last_cpu = cpu;
@ -446,7 +436,7 @@ static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct ta
stts();
} else {
old->thread.fpu.counter = 0;
task_disable_lazy_fpu_restore(old);
old->thread.fpu.last_cpu = -1;
if (fpu.preload) {
new->thread.fpu.counter++;
if (fpu_lazy_restore(new, cpu))

11
arch/x86/include/asm/fpu/types.h
View File

@ -125,7 +125,18 @@ union thread_xstate {
};
struct fpu {
/*
* Records the last CPU on which this context was loaded into
* FPU registers. (In the lazy-switching case we might be
* able to reuse FPU registers across multiple context switches
* this way, if no intermediate task used the FPU.)
*
* A value of -1 is used to indicate that the FPU state in context
* memory is newer than the FPU state in registers, and that the
* FPU state should be reloaded next time the task is run.
*/
unsigned int last_cpu;
unsigned int has_fpu;
union thread_xstate *state;
/*

5
arch/x86/kernel/fpu/core.c
View File

@ -242,8 +242,7 @@ int fpu__copy(struct task_struct *dst, struct task_struct *src)
dst->thread.fpu.counter = 0;
dst->thread.fpu.has_fpu = 0;
dst->thread.fpu.state = NULL;
task_disable_lazy_fpu_restore(dst);
dst->thread.fpu.last_cpu = -1;
if (src_fpu->fpstate_active) {
int err = fpstate_alloc(dst_fpu);
@ -319,7 +318,7 @@ static int fpu__unlazy_stopped(struct task_struct *child)
return -EINVAL;
if (child_fpu->fpstate_active) {
task_disable_lazy_fpu_restore(child);
child->thread.fpu.last_cpu = -1;
return 0;
}