[PATCH] PM: hibernate: add sanity check on power_kobj

[PATCH] PM: hibernate: add sanity check on power_kobj

[Abel Wu]

The @power_kobj is initialized in pm_init() which is the same
initcall level as pm_disk_init(). Although this dependency is
guaranteed based on the current initcall serial execution model,
it would still be better do a cost-less sanity check to avoid
oops once the dependency is broken.

Signed-off-by: Abel Wu <abel.w@icloud.com>
---
 kernel/power/hibernate.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index da0b41914177..060089cc261d 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -1262,6 +1262,9 @@ static const struct attribute_group attr_group = {
 
 static int __init pm_disk_init(void)
 {
+	if (!power_kobj)
+		return -EINVAL;
+
 	return sysfs_create_group(power_kobj, &attr_group);
 }
 
-- 
2.27.0

Re: [PATCH] PM: hibernate: add sanity check on power_kobj

[Pavel Machek]

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On Mon 2021-02-01 02:50:41, Abel Wu wrote:
> The @power_kobj is initialized in pm_init() which is the same
> initcall level as pm_disk_init(). Although this dependency is
> guaranteed based on the current initcall serial execution model,
> it would still be better do a cost-less sanity check to avoid
> oops once the dependency is broken.

I don't believe this is good idea. If the dependency is ever broken,
this will make failure more subtle and harder to debug.

> Signed-off-by: Abel Wu <abel.w@icloud.com>
> ---
>  kernel/power/hibernate.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> index da0b41914177..060089cc261d 100644
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -1262,6 +1262,9 @@ static const struct attribute_group attr_group = {
>  
>  static int __init pm_disk_init(void)
>  {
> +	if (!power_kobj)
> +		return -EINVAL;
> +
>  	return sysfs_create_group(power_kobj, &attr_group);
>  }
>  
> -- 
> 2.27.0

-- 
http://www.livejournal.com/~pavelmachek

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Re: [PATCH] PM: hibernate: add sanity check on power_kobj

[Abel Wu]

> On Feb 1, 2021, at 6:52 PM, Pavel Machek <pavel@ucw.cz> wrote:
> 
> On Mon 2021-02-01 02:50:41, Abel Wu wrote:
>> The @power_kobj is initialized in pm_init() which is the same
>> initcall level as pm_disk_init(). Although this dependency is
>> guaranteed based on the current initcall serial execution model,
>> it would still be better do a cost-less sanity check to avoid
>> oops once the dependency is broken.
> 
> I don't believe this is good idea. If the dependency is ever broken,
> this will make failure more subtle and harder to debug.

Thanks for reviewing. I think the cmdline parameter initcall_debug will
help in this case.
Actually we are trying to make initcalls being called asynchronously to
reduce boot time which is crucial to our cloud-native business. And we
resolve this kind of dependencies by retrying failed initcalls.

Best regards,
	Abel
> 
>> Signed-off-by: Abel Wu <abel.w@icloud.com>
>> ---
>> kernel/power/hibernate.c | 3 +++
>> 1 file changed, 3 insertions(+)
>> 
>> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
>> index da0b41914177..060089cc261d 100644
>> --- a/kernel/power/hibernate.c
>> +++ b/kernel/power/hibernate.c
>> @@ -1262,6 +1262,9 @@ static const struct attribute_group attr_group = {
>> 
>> static int __init pm_disk_init(void)
>> {
>> +	if (!power_kobj)
>> +		return -EINVAL;
>> +
>> 	return sysfs_create_group(power_kobj, &attr_group);
>> }
>> 
>> -- 
>> 2.27.0
> 
> -- 
> http://www.livejournal.com/~pavelmachek

Re: [PATCH] PM: hibernate: add sanity check on power_kobj

[Pavel Machek]

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On Tue 2021-02-02 09:59:11, Abel Wu wrote:
> 
> 
> > On Feb 1, 2021, at 6:52 PM, Pavel Machek <pavel@ucw.cz> wrote:
> > 
> > On Mon 2021-02-01 02:50:41, Abel Wu wrote:
> >> The @power_kobj is initialized in pm_init() which is the same
> >> initcall level as pm_disk_init(). Although this dependency is
> >> guaranteed based on the current initcall serial execution model,
> >> it would still be better do a cost-less sanity check to avoid
> >> oops once the dependency is broken.
> > 
> > I don't believe this is good idea. If the dependency is ever broken,
> > this will make failure more subtle and harder to debug.
> 
> Thanks for reviewing. I think the cmdline parameter initcall_debug will
> help in this case.
> Actually we are trying to make initcalls being called asynchronously to
> reduce boot time which is crucial to our cloud-native business. And we
> resolve this kind of dependencies by retrying failed initcalls.

And this patch is okay if that gets mainlined, but not before.

Best regards,
							Pavel
							
-- 
http://www.livejournal.com/~pavelmachek

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