Re: [PATCH] uswsusp: automatically free the in-memory image once s2disk has finished with it

Rafael J. Wysocki
2009-12-02T21:46:39Z

On Wednesday 02 December 2009, Alan Jenkins wrote:
> The original in-kernel suspend (swsusp) frees the in-memory hibernation
> image before powering off the machine. s2disk doesn't, so there is
> _much_ less free memory when it tries to power off.
>
> This is a gratuitous difference. The userspace suspend interface
> /dev/snapshot only allows the hibernation image to be read once.
> Once the s2disk program has read the last page, we can free the entire
> image.
>
> This avoids a hang after writing the hibernation image which was
> triggered by commit 5f8dcc21211a3d4e3a7a5ca366b469fb88117f61
> "page-allocator: split per-cpu list into one-list-per-migrate-type":
>
> [top of trace lost due to screen height]
> ? shrink_zone
> ? try_to_free_pages
> ? isolate_pages_global
> ? __alloc_pages_nodemask
> ? kthread
> ? __get_free_pages
> ? copy_process
> ? kthread
> ? do_fork
> ...
>
> INFO: task s2disk:2036 blocked for more than 120 seconds
> ...
> Call Trace:
> ...
> ? wait_for_common
> ? default_wake_function
> ? kthread_create
> ? worker_thread
> ? create_workqueue_thread
> ? worker_thread
> ? __create_workqueue_key
> ? stop_machine_create
> ? disable_nonboot_cpus
> ? hibernation_platform_enter
> ? snapshot_ioctl
> ...
> ? sys_ioctl
> ...
>
> Signed-off-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>

Thanks for tracking this, great job!

I'm going to push this patch to Linus in the next batch (before 2.6.32 if I
manage to).

Best,
Rafael

> ---
> kernel/power/user.c | 4 ++++
> 1 files changed, 4 insertions(+), 0 deletions(-)
>
> diff --git a/kernel/power/user.c b/kernel/power/user.c
> index bf0014d..94d0210 100644
> --- a/kernel/power/user.c
> +++ b/kernel/power/user.c
> @@ -165,6 +165,10 @@ static ssize_t snapshot_read(struct file *filp, char __user *buf,
> res = -EFAULT;
> else
> *offp = data->handle.offset;
> + } else {
> + swsusp_free();
> + memset(&data->handle, 0, sizeof(struct snapshot_handle));
> + data->ready = 0;
> }
>
> Unlock:
>