On Wednesday 27 September 2006 12:04, Aubrey wrote:
> inline static void default_idle(void)
> {
> int flag;
>
> while (!need_resched()) {
> leds_switch(LED_OFF);
> local_irq_save(flag);
> if ( likely(!need_resched()) {
> #if defined (ANOMALY_05000244) && defined (CONFIG_BLKFIN_CACHE)
> __asm__("nop; nop;\n");
> #endif
> __asm__(".align 64;\n STI %0; IDLE;\n"
> : %0 (flag): :"cc");
> }
> local_irq_restore(flag);
> leds_switch(LED_ON);
> }
> }======================================
>
> Here, according to design, it's not possible that interrupt occurs
> between "STI %0"(enable interrupt) and "IDLE".
>
> __asm__(".align 64; STI %0; IDLE;" : %0 (x): :"cc");
>
> Robin can explain more details.
Ok, looks good now. Just a few details that don't impact the
functionality:
- Always use 'static inline', not 'inline static', because of C99
- In the kernel, it's more common to use 'asm' than '__asm__'.
- It should probably be 'asm volatile', since gcc might notice
that the output (flag) is not used anywhere and it can therefore
eliminate the asm.
- Usually, I recommend using local_irq_disable() instead of
local_irq_save(flags) when you know that interrupts are enabled
before. It uses one less local variable, which makes it more
efficient on some architectures.
- I'd insert the two NOPs unconditionally here for better
readability.
Arnd <><
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