* [BUG]INFO: suspicious RCU usage for 3.5-rc1+
@ 2012-06-12 8:26 Feng Tang
2012-07-02 21:41 ` Alexander Holler
2012-07-03 6:35 ` [PATCH] leds: heartbeat: fix bug on panic Alexander Holler
0 siblings, 2 replies; 8+ messages in thread
From: Feng Tang @ 2012-06-12 8:26 UTC (permalink / raw)
To: Linux Kernel Mail List; +Cc: Wu, Fengguang, Alexander Holler, Richard Purdie
During Fengguang's build test, we found a problem here:
(x86_64-allyesdebian config)
[ 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
Seems it is caused by doing sleepable option in led_trigger_unregister() inside the panic atomic environment.
The original commit is:
commit 49dca5aebfdeadd4bf27b6cb4c60392147dc35a4
Author: Alexander Holler <holler@ahsoftware.de>
Date: Tue May 29 15:07:29 2012 -0700
leds: heartbeat: stop on shutdown
A halted kernel should not show a heartbeat.
Thanks,
Feng
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [BUG]INFO: suspicious RCU usage for 3.5-rc1+
2012-06-12 8:26 [BUG]INFO: suspicious RCU usage for 3.5-rc1+ Feng Tang
@ 2012-07-02 21:41 ` Alexander Holler
2012-07-03 6:35 ` [PATCH] leds: heartbeat: fix bug on panic Alexander Holler
1 sibling, 0 replies; 8+ messages in thread
From: Alexander Holler @ 2012-07-02 21:41 UTC (permalink / raw)
To: Feng Tang; +Cc: Linux Kernel Mail List, Wu, Fengguang, Richard Purdie
Hello Feng,
sorry for the late answer.
Am 12.06.2012 10:26, schrieb Feng Tang:
> During Fengguang's build test, we found a problem here:
>
> (x86_64-allyesdebian config)
>
> [ 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
>
>
>
> Seems it is caused by doing sleepable option in led_trigger_unregister() inside the panic atomic environment.
>
> The original commit is:
> commit 49dca5aebfdeadd4bf27b6cb4c60392147dc35a4
> Author: Alexander Holler <holler@ahsoftware.de>
> Date: Tue May 29 15:07:29 2012 -0700
>
> leds: heartbeat: stop on shutdown
>
> A halted kernel should not show a heartbeat.
>
Hmm, I'm not very familiar with what happens when a panic occurs and my
tests with panics haven't revealed that (or I didn't have seen it).
I will try to get the same error and will have a deeper look at what
happens in led_trigger_unregister() (and if and how that might be
avoidable) in the next days. Thanks.
Regards,
Alexander
^ permalink raw reply [flat|nested] 8+ messages in thread
* [PATCH] leds: heartbeat: fix bug on panic
2012-06-12 8:26 [BUG]INFO: suspicious RCU usage for 3.5-rc1+ Feng Tang
2012-07-02 21:41 ` Alexander Holler
@ 2012-07-03 6:35 ` Alexander Holler
2012-07-04 7:05 ` Bryan Wu
1 sibling, 1 reply; 8+ messages in thread
From: Alexander Holler @ 2012-07-03 6:35 UTC (permalink / raw)
To: linux-kernel
Cc: Shuah Khan, Richard Purdie, Bryan Wu, Feng Tang, Alexander Holler
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>
---
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 41dc76d..a019fbb 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)
--
1.7.6.5
^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH] leds: heartbeat: fix bug on panic
2012-07-03 6:35 ` [PATCH] leds: heartbeat: fix bug on panic Alexander Holler
@ 2012-07-04 7:05 ` Bryan Wu
2012-07-04 7:11 ` Alexander Holler
0 siblings, 1 reply; 8+ messages in thread
From: Bryan Wu @ 2012-07-04 7:05 UTC (permalink / raw)
To: Alexander Holler; +Cc: linux-kernel, Shuah Khan, Richard Purdie, Feng Tang
On Tue, Jul 3, 2012 at 2:35 PM, Alexander Holler <holler@ahsoftware.de> wrote:
> 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>
> ---
> 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 41dc76d..a019fbb 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;
Can we just set LED as OFF and delete the timer here? because timer is
also useless after a kernel panic.
So we don't need this global static variable here.
-Bryan
> + 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)
> --
> 1.7.6.5
>
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] leds: heartbeat: fix bug on panic
2012-07-04 7:05 ` Bryan Wu
@ 2012-07-04 7:11 ` Alexander Holler
2012-07-04 7:29 ` Bryan Wu
0 siblings, 1 reply; 8+ messages in thread
From: Alexander Holler @ 2012-07-04 7:11 UTC (permalink / raw)
To: Bryan Wu; +Cc: linux-kernel, Shuah Khan, Richard Purdie, Feng Tang
Am 04.07.2012 09:05, schrieb Bryan Wu:
> On Tue, Jul 3, 2012 at 2:35 PM, Alexander Holler <holler@ahsoftware.de> wrote:
>> 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>
>> ---
>> 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 41dc76d..a019fbb 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;
>
> Can we just set LED as OFF and delete the timer here? because timer is
> also useless after a kernel panic.
> So we don't need this global static variable here.
No, the necessary information (heartbeat_trig_data) isn't available here.
Regards,
Alexander
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] leds: heartbeat: fix bug on panic
2012-07-04 7:11 ` Alexander Holler
@ 2012-07-04 7:29 ` Bryan Wu
2012-07-04 7:51 ` Alexander Holler
0 siblings, 1 reply; 8+ messages in thread
From: Bryan Wu @ 2012-07-04 7:29 UTC (permalink / raw)
To: Alexander Holler; +Cc: linux-kernel, Shuah Khan, Richard Purdie, Feng Tang
On Wed, Jul 4, 2012 at 3:11 PM, Alexander Holler <holler@ahsoftware.de> wrote:
> Am 04.07.2012 09:05, schrieb Bryan Wu:
>
>> On Tue, Jul 3, 2012 at 2:35 PM, Alexander Holler <holler@ahsoftware.de>
>> wrote:
>>>
>>> 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>
>>> ---
>>> 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 41dc76d..a019fbb 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;
>>
>>
>> Can we just set LED as OFF and delete the timer here? because timer is
>> also useless after a kernel panic.
>> So we don't need this global static variable here.
>
>
> No, the necessary information (heartbeat_trig_data) isn't available here.
>
Yeah, looks like there is no way to pass heartbeat_trig_data
information to the notifier call function.
Anyway, I will apply this patch to my for-next branch.
Thanks,
--
Bryan Wu <bryan.wu@canonical.com>
Kernel Developer +86.186-168-78255 Mobile
Canonical Ltd. www.canonical.com
Ubuntu - Linux for human beings | www.ubuntu.com
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] leds: heartbeat: fix bug on panic
2012-07-04 7:29 ` Bryan Wu
@ 2012-07-04 7:51 ` Alexander Holler
2012-07-04 7:54 ` Bryan Wu
0 siblings, 1 reply; 8+ messages in thread
From: Alexander Holler @ 2012-07-04 7:51 UTC (permalink / raw)
To: Bryan Wu; +Cc: linux-kernel, Shuah Khan, Richard Purdie, Feng Tang
Am 04.07.2012 09:29, schrieb Bryan Wu:
> Anyway, I will apply this patch to my for-next branch.
Is it already too late for 3.5 (where I introduced the bug)? I know I
should have reacted faster, but I the bug report got down under a ton of
other mails. ;)
Regards,
Alexander
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] leds: heartbeat: fix bug on panic
2012-07-04 7:51 ` Alexander Holler
@ 2012-07-04 7:54 ` Bryan Wu
0 siblings, 0 replies; 8+ messages in thread
From: Bryan Wu @ 2012-07-04 7:54 UTC (permalink / raw)
To: Alexander Holler; +Cc: linux-kernel, Shuah Khan, Richard Purdie, Feng Tang
On Wed, Jul 4, 2012 at 3:51 PM, Alexander Holler <holler@ahsoftware.de> wrote:
> Am 04.07.2012 09:29, schrieb Bryan Wu:
>
>
>> Anyway, I will apply this patch to my for-next branch.
>
>
> Is it already too late for 3.5 (where I introduced the bug)? I know I should
> have reacted faster, but I the bug report got down under a ton of other
> mails. ;)
>
OK, I will put it to my fixes-for-3.5 branch, since this is a real bug fixing.
Thanks,
--
Bryan Wu <bryan.wu@canonical.com>
Kernel Developer +86.186-168-78255 Mobile
Canonical Ltd. www.canonical.com
Ubuntu - Linux for human beings | www.ubuntu.com
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2012-07-04 7:54 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2012-06-12 8:26 [BUG]INFO: suspicious RCU usage for 3.5-rc1+ Feng Tang
2012-07-02 21:41 ` Alexander Holler
2012-07-03 6:35 ` [PATCH] leds: heartbeat: fix bug on panic Alexander Holler
2012-07-04 7:05 ` Bryan Wu
2012-07-04 7:11 ` Alexander Holler
2012-07-04 7:29 ` Bryan Wu
2012-07-04 7:51 ` Alexander Holler
2012-07-04 7:54 ` Bryan Wu
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