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powerpc: Make flush_fp_to_thread() nop when CONFIG_PPC_FPU is disabled 

In the current kernel, the function flush_fp_to_thread() is not
dependent on CONFIG_PPC_FPU. So most invocations of this function
is not wrapped by CONFIG_PPC_FPU. Even through we don't really
save the FPRs to the thread struct if CONFIG_PPC_FPU is not enabled,
but there does have some runtime overhead such as the check for
tsk->thread.regs and preempt disable and enable. It really make
no sense to do that. So make it a nop when CONFIG_PPC_FPU is
disabled. Also remove the wrapped #ifdef CONFIG_PPC_FPU
when invoking this function.

Signed-off-by: Kevin Hao <haokexin@gmail.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Kevin Hao 2013-07-14 17:02:05 +08:00 committed by Benjamin Herrenschmidt
parent 662499d04b
commit 037f0eed57
3 changed files with 9 additions and 3 deletions
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7
arch/powerpc/include/asm/switch_to.h
View File

@ -19,7 +19,6 @@ extern struct task_struct *_switch(struct thread_struct *prev,
extern void giveup_fpu(struct task_struct *);
extern void load_up_fpu(void);
extern void enable_kernel_fp(void);
extern void flush_fp_to_thread(struct task_struct *);
extern void enable_kernel_altivec(void);
extern void load_up_altivec(struct task_struct *);
extern int emulate_altivec(struct pt_regs *);
@ -37,6 +36,12 @@ static inline void discard_lazy_cpu_state(void)
}
#endif
#ifdef CONFIG_PPC_FPU
extern void flush_fp_to_thread(struct task_struct *);
#else
static inline void flush_fp_to_thread(struct task_struct *t) { }
#endif
#ifdef CONFIG_ALTIVEC
extern void flush_altivec_to_thread(struct task_struct *);
extern void giveup_altivec(struct task_struct *);

2
arch/powerpc/kernel/process.c
View File

@ -74,6 +74,7 @@ struct task_struct *last_task_used_vsx = NULL;
struct task_struct *last_task_used_spe = NULL;
#endif
#ifdef CONFIG_PPC_FPU
/*
* Make sure the floating-point register state in the
* the thread_struct is up to date for task tsk.
@ -107,6 +108,7 @@ void flush_fp_to_thread(struct task_struct *tsk)
}
}
EXPORT_SYMBOL_GPL(flush_fp_to_thread);
#endif
void enable_kernel_fp(void)
{

3
arch/powerpc/math-emu/math.c
View File

@ -7,6 +7,7 @@
#include <asm/uaccess.h>
#include <asm/reg.h>
#include <asm/switch_to.h>
#include <asm/sfp-machine.h>
#include <math-emu/double.h>
@ -433,9 +434,7 @@ do_mathemu(struct pt_regs *regs)
* is flushed into the thread_struct before attempting
* emulation
*/
#ifdef CONFIG_PPC_FPU
flush_fp_to_thread(current);
#endif
eflag = func(op0, op1, op2, op3);