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

From: Abel Wu <abel.w@icloud.com>
To: Pavel Machek <pavel@ucw.cz>
Cc: rjw@rjwysocki.net, linux-pm@vger.kernel.org,
	linux-kernel@vger.kernel.org, hewenliang4@huawei.com,
	wuyun.wu@huawei.com
Subject: Re: [PATCH] PM: hibernate: add sanity check on power_kobj
Date: Tue, 2 Feb 2021 09:59:11 +0800	[thread overview]
Message-ID: <F87648CF-E5D6-41C7-9F4E-87A4BA2A4786@icloud.com> (raw)
In-Reply-To: <20210201105243.GA23135@duo.ucw.cz>

> 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