Re: [PATCH v1] PM: hibernate: Avoid redundant resume_device assignment in resume_store()

[Zihuan Zhang]

Hi Rafael,

在 2025/7/3 02:51, Rafael J. Wysocki 写道:
> On Fri, May 30, 2025 at 12:00 PM Zihuan Zhang <zhangzihuan@xxxxxxxxxx> wrote:
> > In resume_store(), if the device number written to /sys/power/resume
> > is the same as the current swsusp_resume_device, we can skip reassignment.
> > This avoids unnecessary locking and improves efficiency slightly.
> >
> > Signed-off-by: Zihuan Zhang <zhangzihuan@xxxxxxxxxx>
> > ---
> >   kernel/power/hibernate.c | 3 +++
> >   1 file changed, 3 insertions(+)
> >
> > diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> > index 519fb09de5e0..504a1c2465ce 100644
> > --- a/kernel/power/hibernate.c
> > +++ b/kernel/power/hibernate.c
> > @@ -1291,6 +1291,9 @@ static ssize_t resume_store(struct kobject *kobj, struct kobj_attribute *attr,
> >          if (error)
> >                  return error;
> >
> > +       if (dev == swsusp_resume_device)
> > +               return n;
> > +
> The main purpose of this function is to run software_resume(), not to
> set swsusp_resume_device.  You're breaking it with this change.
Thank you for the feedback.

You’re absolutely right — I misunderstood the primary role of 
resume_store() as being only to update swsusp_resume_device, and I 
overlooked that its main purpose is to trigger software_resume().

I’ll drop this patch accordingly. Thanks again for pointing this out.

> >          sleep_flags = lock_system_sleep();
> >          swsusp_resume_device = dev;
> >          unlock_system_sleep(sleep_flags);
> > --
> > 2.25.1
Best regards,
Zihuan Zhang