Messages in this thread Patch in this message | | | Date | Fri, 13 Apr 2012 08:56:18 -0600 | From | Tim Gardner <> | Subject | Re: [PATCH 01/18] led-triggers: create a trigger for CPU activity |
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On 04/13/2012 05:26 AM, Bryan Wu wrote: > Attempting to consolidate the ARM LED code, this removes the > custom RealView LED trigger code to turn LEDs on and off in > response to CPU activity and replace it with a standard trigger. > > (bryan.wu@canonical.com: > It moves arch/arm/kernel/leds.c syscore stubs into this trigger. > It also provides ledtrig_cpu trigger event stub in <linux/leds.h>. > Although it was inspired by ARM work, it can be used in other arch.) > > Cc: Richard Purdie <rpurdie@rpsys.net> > Signed-off-by: Linus Walleij <linus.walleij@linaro.org> > Signed-off-by: Bryan Wu <bryan.wu@canonical.com> > > Reviewed-by: Jamie Iles <jamie@jamieiles.com> > Tested-by: Jochen Friedrich <jochen@scram.de> > --- > drivers/leds/Kconfig | 10 ++++ > drivers/leds/Makefile | 1 + > drivers/leds/ledtrig-cpu.c | 133 ++++++++++++++++++++++++++++++++++++++++++++ > include/linux/leds.h | 23 ++++++++ > 4 files changed, 167 insertions(+) > create mode 100644 drivers/leds/ledtrig-cpu.c > > diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig > index 9f2b8dd..6e445a0 100644 > --- a/drivers/leds/Kconfig > +++ b/drivers/leds/Kconfig > @@ -457,6 +457,16 @@ config LEDS_TRIGGER_BACKLIGHT > > If unsure, say N. > > +config LEDS_TRIGGER_CPU > + tristate "LED CPU Trigger" > + depends on LEDS_TRIGGERS > + help > + This allows LEDs to be controlled by active CPUs. This shows > + the active CPUs across an array of LEDs so you can see what > + CPUs are active on the system at any given moment. > + > + If unsure, say N. > + > config LEDS_TRIGGER_GPIO > tristate "LED GPIO Trigger" > depends on LEDS_TRIGGERS > diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile > index 14481cf..8bb20e6 100644 > --- a/drivers/leds/Makefile > +++ b/drivers/leds/Makefile > @@ -55,4 +55,5 @@ obj-$(CONFIG_LEDS_TRIGGER_IDE_DISK) += ledtrig-ide-disk.o > obj-$(CONFIG_LEDS_TRIGGER_HEARTBEAT) += ledtrig-heartbeat.o > obj-$(CONFIG_LEDS_TRIGGER_BACKLIGHT) += ledtrig-backlight.o > obj-$(CONFIG_LEDS_TRIGGER_GPIO) += ledtrig-gpio.o > +obj-$(CONFIG_LEDS_TRIGGER_CPU) += ledtrig-cpu.o > obj-$(CONFIG_LEDS_TRIGGER_DEFAULT_ON) += ledtrig-default-on.o > diff --git a/drivers/leds/ledtrig-cpu.c b/drivers/leds/ledtrig-cpu.c > new file mode 100644 > index 0000000..52ef19c > --- /dev/null > +++ b/drivers/leds/ledtrig-cpu.c > @@ -0,0 +1,133 @@ > +/* > + * ledtrig-cpu.c - LED trigger based on CPU activity > + * > + * This LED trigger will be registered for each possible CPU and named as > + * cpu0, cpu1, cpu2, cpu3, etc. > + * > + * It can be binded with any LEDs as other triggers does, either in board > + * file or via sysfs interface. > + *
"It can be bound to any LED just like other triggers using either a board file or via sysfs interface."
> + * An API named ledtrig_cpu is exported for any user, who want to add CPU > + * activity indication in their code > + * > + * Copyright 2011 Linus Walleij <linus.walleij@linaro.org> > + * Copyright 2011 - 2012 Bryan Wu <bryan.wu@canonical.com> > + * > + * This program is free software; you can redistribute it and/or modify > + * it under the terms of the GNU General Public License version 2 as > + * published by the Free Software Foundation. > + * > + */ > + > +#include <linux/module.h> > +#include <linux/kernel.h> > +#include <linux/init.h> > +#include <linux/slab.h> > +#include <linux/percpu.h> > +#include <linux/syscore_ops.h> > +#include "leds.h" > + > +#define MAX_NAME_LEN 8 > +
This length accommodates up to 10000 CPUs. How long will that suffice ?
> +static DEFINE_PER_CPU(struct led_trigger *, cpu_trig); > +static DEFINE_PER_CPU(char [MAX_NAME_LEN], trig_name); > + > +void ledtrig_cpu(enum cpu_led_event ledevt) > +{ > + struct led_trigger *trig = __get_cpu_var(cpu_trig); > + > + if (!trig) > + return;
I don't think __get_cpu_var(cpu_trig) _should_ ever return NULL. See discussion about exclusion below in ledtrig_cpu_init().
> + > + /* 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, LED_FULL); > + break; > + > + case CPU_LED_IDLE_START: > + case CPU_LED_STOP: > + case CPU_LED_HALTED: > + /* Will turn the LED off */ > + led_trigger_event(trig, LED_OFF); > + break; > + > + default: > + /* Will leave the LED as it is */ > + break; > + } > +} > +EXPORT_SYMBOL(ledtrig_cpu); > + > +static int ledtrig_cpu_syscore_suspend(void) > +{ > + ledtrig_cpu(CPU_LED_STOP); > + return 0; > +} > + > +static void ledtrig_cpu_syscore_resume(void) > +{ > + ledtrig_cpu(CPU_LED_START); > +} > + > +static void ledtrig_cpu_syscore_shutdown(void) > +{ > + ledtrig_cpu(CPU_LED_HALTED); > +} > + > +static struct syscore_ops ledtrig_cpu_syscore_ops = { > + .shutdown = ledtrig_cpu_syscore_shutdown, > + .suspend = ledtrig_cpu_syscore_suspend, > + .resume = ledtrig_cpu_syscore_resume, > +}; > + > +static int __init ledtrig_cpu_init(void) > +{ > + int cpu; > + > + /* > + * Registering CPU led trigger for each CPU cores here > + * ignores CPU hotplug, but after this CPU hotplug works > + * fine with this trigger. > + */ > + for_each_possible_cpu(cpu) { > + struct led_trigger *trig; > + char *name = per_cpu(trig_name, cpu); > + > + snprintf(name, MAX_NAME_LEN, "cpu%d", cpu); > + led_trigger_register_simple(name, &trig);
Check for trig == NULL. led_trigger_register_simple() does a kzalloc(GFP_KERNEL). You'll also have to unwind any successful registrations. Perhaps carve the guts out of ledtrig_cpu_exit() into a function that can be called from either place.
Furthermore, I think there is a race here. As soon as led_trigger_register_simple() has completed, then the trigger is available for use. Won't you need some kind of exclusion to block consumers before trig is assigned ? There is a similar problem in ledtrig_cpu().
> + per_cpu(cpu_trig, cpu) = trig; > + > + pr_info("LED trigger %s indicate activity on CPU %d\n", > + trig->name, cpu);
This seems like an unnecessary log filler, especially as the number of CPUs becomes large. How about just a single line after the loop completes ?
> + } > + > + register_syscore_ops(&ledtrig_cpu_syscore_ops); > + > + return 0; > +} > +module_init(ledtrig_cpu_init); > + > +static void __exit ledtrig_cpu_exit(void) > +{ > + int cpu; > + > + for_each_possible_cpu(cpu) { > + struct led_trigger *trig = per_cpu(cpu_trig, cpu); > + char *name = per_cpu(trig_name, cpu); > + > + led_trigger_unregister_simple(trig); > + per_cpu(cpu_trig, cpu) = NULL; > + memset(name, 0, MAX_NAME_LEN); > + } > + > + unregister_syscore_ops(&ledtrig_cpu_syscore_ops); > +} > +module_exit(ledtrig_cpu_exit); > + > +MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>"); > +MODULE_AUTHOR("Bryan Wu <bryan.wu@canonical.com>"); > +MODULE_DESCRIPTION("CPU LED trigger"); > +MODULE_LICENSE("GPL"); > diff --git a/include/linux/leds.h b/include/linux/leds.h > index 5884def..1215b94 100644 > --- a/include/linux/leds.h > +++ b/include/linux/leds.h > @@ -210,4 +210,27 @@ struct gpio_led_platform_data { > struct platform_device *gpio_led_register_device( > int id, const struct gpio_led_platform_data *pdata); > > +enum cpu_led_event { > + CPU_LED_IDLE_START, /* CPU enters idle */ > + CPU_LED_IDLE_END, /* CPU idle ends */ > + CPU_LED_START, /* Machine starts, especially resume */ > + CPU_LED_STOP, /* Machine stops, especially suspend */ > + CPU_LED_HALTED, /* Machine shutdown */ > +}; > +#if defined(CONFIG_LEDS_TRIGGER_CPU) || defined(CONFIG_LEDS_TRIGGER_CPU_MODULE) > +/** > + * ledtrig_cpu - emit a CPU event as a trigger > + * @evt: CPU event to be emitted > + * > + * Emit a CPU event on a CPU core, which will trigger a > + * binded LED to turn on or turn off. > + */ > +extern void ledtrig_cpu(enum cpu_led_event evt); > +#else > +static inline void ledtrig_cpu(enum cpu_led_event evt) > +{ > + return; > +} > +#endif > + > #endif /* __LINUX_LEDS_H_INCLUDED */
-- Tim Gardner tim.gardner@canonical.com
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