linux-kernel - Re: [PATCH] PM/Hibernate: Thaw kernel threads in hibernation

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Date:	Thu, 2 Feb 2012 20:11:55 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Cc:	pavel@....cz, len.brown@...el.com, tj@...nel.org,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PM/Hibernate: Thaw kernel threads in hibernation_snapshot() in error/test path

On Thursday, February 02, 2012, Srivatsa S. Bhat wrote:
> In the hibernation call path, the kernel threads are frozen inside
> hibernation_snapshot(). If we happen to encounter an error further down
> the road or if we are exiting early due to a successful freezer test,
> then thaw kernel threads before returning to the caller.
> 
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
> ---
> 
>  kernel/power/hibernate.c |    6 ++++--
>  kernel/power/user.c      |    8 ++------
>  2 files changed, 6 insertions(+), 8 deletions(-)
> 
> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> index a5d4cf0..c6dee73 100644
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -343,13 +343,13 @@ int hibernation_snapshot(int platform_mode)
>  		 * successful freezer test.
>  		 */
>  		freezer_test_done = true;
> -		goto Cleanup;
> +		goto Thaw;
>  	}
>  
>  	error = dpm_prepare(PMSG_FREEZE);
>  	if (error) {
>  		dpm_complete(PMSG_RECOVER);
> -		goto Cleanup;
> +		goto Thaw;
>  	}
>  
>  	suspend_console();
> @@ -385,6 +385,8 @@ int hibernation_snapshot(int platform_mode)
>  	platform_end(platform_mode);
>  	return error;
>  
> + Thaw:
> +	thaw_kernel_threads();

Actaully, no.  You have to do swsusp_free() before thawing, otherwise
some allocations made by the just thawed kernel threads may fail.

>   Cleanup:
>  	swsusp_free();
>  	goto Close;
> diff --git a/kernel/power/user.c b/kernel/power/user.c
> index 3e10007..7bee91f 100644
> --- a/kernel/power/user.c
> +++ b/kernel/power/user.c
> @@ -249,16 +249,12 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
>  		}
>  		pm_restore_gfp_mask();
>  		error = hibernation_snapshot(data->platform_support);
> -		if (error) {
> -			thaw_kernel_threads();
> -		} else {
> +		if (!error) {
>  			error = put_user(in_suspend, (int __user *)arg);
>  			if (!error && !freezer_test_done)
>  				data->ready = 1;
> -			if (freezer_test_done) {
> +			if (freezer_test_done)
>  				freezer_test_done = false;
> -				thaw_kernel_threads();
> -			}
>  		}
>  		break;

Overall, this seems to be a cleanup, or is it a bug fix?

Thanks,
Rafael
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