Re: [PATCH 2/3] PM: add sysfs attributes for additional suspend/resume metrics

[Joshua Crofts <crofts@kernel.org>]

On Tue, 10 Nov 2026 12:29:11 -0500
Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:

...

> > +static ssize_t runtime_resume_count_show(struct device *dev,
> > +					 struct device_attribute *attr,
> > +					 char *buf)
> > +{
> > +	u64 count;
> > +
> > +	spin_lock_irq(&dev->power.lock);
> > +	count = dev->power.resume_count;
> > +	spin_unlock_irq(&dev->power.lock);  
> 
> Why is a lock needed at all?  The value isn't going to "smear", it will
> change right after the lock anyway.

On 64-bit systems an aligned u64 read is atomic, but on 32-bit systems it
gets split into two 32-bit loads. Without locking, the read can tear
between the upper and lower halves.

> And if you need one, why not a guard()?

Yeah, I realized this after sending the series out, nevertheless
Sashiko flagged some other stuff so I thought I'd fixup in v2.

Thanks!

-- 
Kind regards,
Joshua Crofts