diff options
| author | Alexander Holler <holler@ahsoftware.de> | 2012-07-03 14:35:47 +0800 |
|---|---|---|
| committer | Bryan Wu <bryan.wu@canonical.com> | 2012-07-04 15:55:19 +0800 |
| commit | fb31fbeb647ed1910290712c13f11f1db09e5506 (patch) | |
| tree | 7fec769975f1c38c5c1d10856404a7713550dbea /drivers | |
| parent | 9e85a6f9dc231f3ed3c1dc1b12217505d970142a (diff) | |
| download | lwn-fb31fbeb647ed1910290712c13f11f1db09e5506.tar.gz lwn-fb31fbeb647ed1910290712c13f11f1db09e5506.zip | |
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: [<ffffffff82f85962>] do_page_fault+0x193/0x390
[ 1526.520230] #1: (panic_lock){+.+...}, at: [<ffffffff82ed2830>] panic+0x37/0x1d3
[ 1526.520230] #2: (rcu_read_lock){.+.+..}, at: [<ffffffff810b9b28>] 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] [<ffffffff810e1570>] lockdep_rcu_suspicious+0x109/0x112
[ 1526.520230] [<ffffffff810bfe3a>] rcu_preempt_sleep_check+0x45/0x47
[ 1526.520230] [<ffffffff810bfe5a>] __might_sleep+0x1e/0x19a
[ 1526.520230] [<ffffffff82f8010e>] down_write+0x26/0x81
[ 1526.520230] [<ffffffff8276a966>] led_trigger_unregister+0x1f/0x9c
[ 1526.520230] [<ffffffff8276def5>] heartbeat_reboot_notifier+0x15/0x19
[ 1526.520230] [<ffffffff82f85bf5>] notifier_call_chain+0x96/0xcd
[ 1526.520230] [<ffffffff82f85cba>] __atomic_notifier_call_chain+0x8e/0xff
[ 1526.520230] [<ffffffff81094b7c>] ? kmsg_dump+0x37/0x1eb
[ 1526.520230] [<ffffffff82f85d3f>] atomic_notifier_call_chain+0x14/0x16
[ 1526.520230] [<ffffffff82ed28e1>] panic+0xe8/0x1d3
[ 1526.520230] [<ffffffff811473e2>] 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 <holler@ahsoftware.de>
Signed-off-by: Bryan Wu <bryan.wu@canonical.com>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/leds/ledtrig-heartbeat.c | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/drivers/leds/ledtrig-heartbeat.c b/drivers/leds/ledtrig-heartbeat.c index 41dc76db4311..a019fbb70880 100644 --- a/drivers/leds/ledtrig-heartbeat.c +++ b/drivers/leds/ledtrig-heartbeat.c @@ -21,6 +21,8 @@ #include <linux/reboot.h> #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) |