From fb31fbeb647ed1910290712c13f11f1db09e5506 Mon Sep 17 00:00:00 2001 From: Alexander Holler Date: Tue, 3 Jul 2012 14:35:47 +0800 Subject: leds: heartbeat: fix bug on panic With commit 49dca5aebfdeadd4bf27b6cb4c60392147dc35a4 I introduced a bug (visible if CONFIG_PROVE_RCU is enabled) which occures when a panic has happened: [ 1526.520230] =============================== [ 1526.520230] [ INFO: suspicious RCU usage. ] [ 1526.520230] 3.5.0-rc1+ #12 Not tainted [ 1526.520230] ------------------------------- [ 1526.520230] /c/kernel-tests/mm/include/linux/rcupdate.h:436 Illegal context switch in RCU read-side critical section! [ 1526.520230] [ 1526.520230] other info that might help us debug this: [ 1526.520230] [ 1526.520230] [ 1526.520230] rcu_scheduler_active = 1, debug_locks = 0 [ 1526.520230] 3 locks held by net.agent/3279: [ 1526.520230] #0: (&mm->mmap_sem){++++++}, at: [] do_page_fault+0x193/0x390 [ 1526.520230] #1: (panic_lock){+.+...}, at: [] panic+0x37/0x1d3 [ 1526.520230] #2: (rcu_read_lock){.+.+..}, at: [] rcu_lock_acquire+0x0/0x29 [ 1526.520230] [ 1526.520230] stack backtrace: [ 1526.520230] Pid: 3279, comm: net.agent Not tainted 3.5.0-rc1+ #12 [ 1526.520230] Call Trace: [ 1526.520230] [] lockdep_rcu_suspicious+0x109/0x112 [ 1526.520230] [] rcu_preempt_sleep_check+0x45/0x47 [ 1526.520230] [] __might_sleep+0x1e/0x19a [ 1526.520230] [] down_write+0x26/0x81 [ 1526.520230] [] led_trigger_unregister+0x1f/0x9c [ 1526.520230] [] heartbeat_reboot_notifier+0x15/0x19 [ 1526.520230] [] notifier_call_chain+0x96/0xcd [ 1526.520230] [] __atomic_notifier_call_chain+0x8e/0xff [ 1526.520230] [] ? kmsg_dump+0x37/0x1eb [ 1526.520230] [] atomic_notifier_call_chain+0x14/0x16 [ 1526.520230] [] panic+0xe8/0x1d3 [ 1526.520230] [] out_of_memory+0x15d/0x1d3 So in case of a panic, now just turn of the LED. Other approaches like scheduling a work to unregister the trigger aren't working because there isn't much which still runs after a panic occured (except timers). Signed-off-by: Alexander Holler Signed-off-by: Bryan Wu --- drivers/leds/ledtrig-heartbeat.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/drivers/leds/ledtrig-heartbeat.c b/drivers/leds/ledtrig-heartbeat.c index 41dc76db431..a019fbb7088 100644 --- a/drivers/leds/ledtrig-heartbeat.c +++ b/drivers/leds/ledtrig-heartbeat.c @@ -21,6 +21,8 @@ #include #include "leds.h" +static int panic_heartbeats; + struct heartbeat_trig_data { unsigned int phase; unsigned int period; @@ -34,6 +36,11 @@ static void led_heartbeat_function(unsigned long data) unsigned long brightness = LED_OFF; unsigned long delay = 0; + if (unlikely(panic_heartbeats)) { + led_set_brightness(led_cdev, LED_OFF); + return; + } + /* acts like an actual heart beat -- ie thump-thump-pause... */ switch (heartbeat_data->phase) { case 0: @@ -111,12 +118,19 @@ static int heartbeat_reboot_notifier(struct notifier_block *nb, return NOTIFY_DONE; } +static int heartbeat_panic_notifier(struct notifier_block *nb, + unsigned long code, void *unused) +{ + panic_heartbeats = 1; + return NOTIFY_DONE; +} + static struct notifier_block heartbeat_reboot_nb = { .notifier_call = heartbeat_reboot_notifier, }; static struct notifier_block heartbeat_panic_nb = { - .notifier_call = heartbeat_reboot_notifier, + .notifier_call = heartbeat_panic_notifier, }; static int __init heartbeat_trig_init(void) -- cgit v1.2.3