linux-kernel - Re: [PATCH v3] PM / sleep: add configurable delay for pm

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Message-ID: <06bcea82-11d5-4dcf-8331-c073e6d9078f@infradead.org>
Date: Wed, 7 May 2025 08:49:20 -0700
From: Randy Dunlap <rdunlap@...radead.org>
To: Zihuan Zhang <zhangzihuan@...inos.cn>, corbet@....net, rafael@...nel.org,
 len.brown@...el.com, pavel@...nel.org, akpm@...ux-foundation.org,
 paulmck@...nel.org, rostedt@...dmis.org, thuth@...hat.com, bp@...en8.de,
 ardb@...nel.org, gregkh@...uxfoundation.org
Cc: linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-pm@...r.kernel.org
Subject: Re: [PATCH v3] PM / sleep: add configurable delay for pm_test



On 5/6/25 11:35 PM, Zihuan Zhang wrote:
> This patch turns this 5 second delay into a configurable module
> parameter, so users can determine how long to wait in this
> pseudo-hibernate state before resuming the system.
> 
> The configurable delay parameter has been added to suspend and
> synchronized to hibernation.
> 
> Example (wait 30 seconds);
> 
>   # echo 30 > /sys/module/hibernate/parameters/pm_test_delay
>   # echo core > /sys/power/pm_test
> 
> Signed-off-by: Zihuan Zhang <zhangzihuan@...inos.cn>

Looks good. Thanks.

Reviewed-by: Randy Dunlap <rdunlap@...radead.org>

> ---
> v3:
>  - Fix the location of the hibernate.pm_test_delay parameter in
>    kernel-parameters.txt.
>  - Update ‘[hibernate]’ to ‘[HIBERNATION]’
> v2:
>  - Fix typos.
> ---
>  Documentation/admin-guide/kernel-parameters.txt | 7 +++++++
>  kernel/power/hibernate.c                        | 9 +++++++--
>  2 files changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index d9fd26b95b34..a110cbb37f20 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1828,6 +1828,13 @@
>  				lz4: Select LZ4 compression algorithm to
>  				compress/decompress hibernation image.
>  
> +	hibernate.pm_test_delay=
> +			[HIBERNATION]
> +			Sets the number of seconds to remain in a hibernation test
> +			mode before resuming the system (see
> +			/sys/power/pm_test). Only available when CONFIG_PM_DEBUG
> +			is set. Default value is 5.
> +
>  	highmem=nn[KMG]	[KNL,BOOT,EARLY] forces the highmem zone to have an exact
>  			size of <nn>. This works even on boxes that have no
>  			highmem otherwise. This also works to reduce highmem
> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> index 23c0f4e6cb2f..485133af884d 100644
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -133,10 +133,15 @@ bool system_entering_hibernation(void)
>  EXPORT_SYMBOL(system_entering_hibernation);
>  
>  #ifdef CONFIG_PM_DEBUG
> +static unsigned int pm_test_delay = 5;
> +module_param(pm_test_delay, uint, 0644);
> +MODULE_PARM_DESC(pm_test_delay,
> +		 "Number of seconds to wait before resuming from hibernation test");
>  static void hibernation_debug_sleep(void)
>  {
> -	pr_info("debug: Waiting for 5 seconds.\n");
> -	mdelay(5000);
> +	pr_info("hibernation debug: Waiting for %d second(s).\n",
> +		pm_test_delay);
> +	mdelay(pm_test_delay * 1000);
>  }
>  
>  static int hibernation_test(int level)

-- 
~Randy