Hi!
> Currently there is one CPU led trigger per cpu ('cpu0', 'cpu1', ...)
>
> This patch adds a new trigger, 'cpu', with brightness proportional to
> the number of active CPUs.
>
> If multiple brightness levels aren't supported on the LED,
> it effectively indicates if there is any CPU active.
>
> This is particularly useful on tiny linux boards with more CPU cores than LED pins.
> +static struct led_trigger_cpu_all all_trig;
> +
> +static bool ledtrig_cpu_initialized;
Umm. This variable looks quite like a lock, but without barriers etc. Are you sure that is ok?
> @@ -47,26 +57,44 @@ static DEFINE_PER_CPU(struct led_trigger_cpu, cpu_trig);
> void ledtrig_cpu(enum cpu_led_event ledevt)
> {
> struct led_trigger_cpu *trig = this_cpu_ptr(&cpu_trig);
> + bool is_active = trig->cpu_is_active;
> +
> + /* Ignore if this is being called before initialization. */
> + if (!ledtrig_cpu_initialized)
> + return;
>
> /* Locate the correct CPU LED */
> switch (ledevt) {
> case CPU_LED_IDLE_END:
> case CPU_LED_START:
> /* Will turn the LED on, max brightness */
> - led_trigger_event(trig->_trig, LED_FULL);
> + is_active = true;
> break;
>
> case CPU_LED_IDLE_START:
> case CPU_LED_STOP:
> case CPU_LED_HALTED:
> /* Will turn the LED off */
> - led_trigger_event(trig->_trig, LED_OFF);
> + is_active = false;
> break;
>
> default:
> /* Will leave the LED as it is */
> break;
> }
> +
> + if (is_active != trig->cpu_is_active) {
> + // Update trigger state
C style comments, please.
> + trig->cpu_is_active = is_active;
> + atomic_add(is_active ? 1 : -1, &all_trig.num_active);
In particular, are you sure that with all the activity during startup, it can't get
desynchronized?
Hmm. is_initialized should be atomic_t, or set_bit should be used. But it will
probably not cause problems in practice.
I guess the trigger actually will self-synchronize with the actual CPU state,
eventually. So I guess it is ok, but...
> + led_trigger_event(all_trig._trig,
> + LED_FULL * atomic_read(&all_trig.num_active) /
> + num_present_cpus());
DIV_ROUND_UP? :-)
THanks,
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
