Re: [linux-pm] [PATCH 2/4] PM / Loss: power loss management
From: Rafael J. Wysocki
Date: Thu May 19 2011 - 16:52:24 EST
On Thursday, May 19, 2011, Alan Stern wrote:
> On Thu, 19 May 2011, Davide Ciminaghi wrote:
>
> > I'm not completely sure about this. What we wanted to do was to avoid powering
> > down the mmc while it is physically writing data into its internal memory.
> > If we force a sync when the power loss warning event warning happens,
> > it is very difficult to be able to guarantee that all buffered data will be
> > written before power actually dies. So we preferred to follow another strategy:
> > let the mmc finish any running write operation, and then stop its request
> > queue. If power really goes down, then we hope that the file system journal
> > will fix things on next boot (yes, some data could get lost, but the fs should
> > still be mountable). On the other hand, if power resumes, nothing bad should
> > happen for user space processes.
>
> You could consider a totally different approach.
>
> Each platform will have a different set of high-power devices it wants
> to turn off when a power-loss warning occurs. So instead of changing
> the core PM interface, you could add a new "power_loss" notifier list.
> Only the most critical drivers would need to listen for notifications,
> and this could be different drivers on different platforms.
Moreover, it would allow not only drivers, but also filesystems (for
one example) to get notifications.
Thanks,
Rafael
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/