I'm using same SDcard image on RPi2 and RPi3.
Since upgradeing kernel 4.9.11 to 4.9.13 setting /sys/class/leds/led1/trigger to heartbeat
triggers crashes during boot process:
$this->bbcode_second_pass_code('', '[ OK ] Mounted /boot.
[ OK ] Reached target Local File Systems.
Starting Create Volatile Files and Directories...
[ OK ] Started Create Volatile Files and Directories.
Starting Network Time Synchronization...
[ 11.475306] BUG: scheduling while atomic: swapper/0/0/0x00000100
[ 11.558799] Modules linked in:[ 11.558882] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.9.13-3-ARCH #1
[ 11.558885] Hardware name: BCM2835
[ 11.558923] [<8010ead0>] (unwind_backtrace) from [<8010b65c>] (show_stack+0x10/0x14)
[ 11.558941] [<8010b65c>] (show_stack) from [<80679b28>] (dump_stack+0x9c/0xc4)
[ 11.558957] [<80679b28>] (dump_stack) from [<80151404>] (__schedule_bug+0x58/0x84)
[ 11.558976] [<80151404>] (__schedule_bug) from [<809bf84c>] (__schedule+0x67c/0x88c)
[ 11.558990] [<809bf84c>] (__schedule) from [<809bfaa4>] (schedule+0x48/0xa0)
[ 11.559006] [<809bfaa4>] (schedule) from [<809c2c7c>] (schedule_timeout+0x230/0x388)
[ 11.559020] [<809c2c7c>] (schedule_timeout) from [<809c0600>] (wait_for_common+0xb8/0x1a0)
[ 11.559036] [<809c0600>] (wait_for_common) from [<8088655c>] (rpi_firmware_transaction+0x5c/0xbc)
[ 11.559051] [<8088655c>] (rpi_firmware_transaction) from [<808866a0>] (rpi_firmware_property_list+0xe4/0x228)
[ 11.559064] [<808866a0>] (rpi_firmware_property_list) from [<8088684c>] (rpi_firmware_property+0x68/0xa0)
[ 11.559084] [<8088684c>] (rpi_firmware_property) from [<806b7228>] (brcmexp_gpio_set+0x40/0x80)
[ 11.559099] [<806b7228>] (brcmexp_gpio_set) from [<808856f4>] (led_heartbeat_function+0x58/0x118)
[ 11.559116] [<808856f4>] (led_heartbeat_function) from [<80190adc>] (call_timer_fn+0x30/0x188)
[ 11.559129] [<80190adc>] (call_timer_fn) from [<80190d10>] (expire_timers+0xdc/0x164)
[ 11.559141] [<80190d10>] (expire_timers) from [<80190e28>] (run_timer_softirq+0x90/0x1c8)
[ 11.559159] [<80190e28>] (run_timer_softirq) from [<8012f810>] (__do_softirq+0xc0/0x2e8)
[ 11.559174] [<8012f810>] (__do_softirq) from [<8012fd2c>] (irq_exit+0xc4/0x140)
[ 11.559192] [<8012fd2c>] (irq_exit) from [<8017f834>] (__handle_domain_irq+0x58/0xb8)
[ 11.559208] [<8017f834>] (__handle_domain_irq) from [<809c42b8>] (__irq_svc+0x58/0x74)
[ 11.559225] [<809c42b8>] (__irq_svc) from [<80108330>] (arch_cpu_idle+0x30/0x3c)
[ 11.559246] [<80108330>] (arch_cpu_idle) from [<8016fe98>] (cpu_startup_entry+0xd0/0x150)
[ 11.559269] [<8016fe98>] (cpu_startup_entry) from [<80e00c80>] (start_kernel+0x378/0x408)
[ 11.559303] ------------[ cut here ]------------
[ 11.559313] WARNING: CPU: 0 PID: 0 at kernel/time/timer.c:1315 call_timer_fn+0x160/0x188
[ 11.559322] timer: led_heartbeat_function+0x0/0x118 preempt leak: 00000100 -> 00000000
...
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Untervoltage Sign appears when BUG is triggered.
System crashes or kernel spitting endless error messages and boot does never finish.
Power LED function settings are no really supported on RPi 3 but setting the function to heartbeat did
no harm in kernel 4.4 series. No issues when leaving default since 4.9.13.
kr roland