On 6 November 2011 08:12, Diego <elc...@kde.org> wrote:
> Hi list,
>
> I am trying to debug this problem in a system I am developing:
>
> at some point I need to write a number to a file, and then reboot via an
> external device the machine. That device will cut of the power for a
> moment,
> and the machine will power on again (this is to overcome a fault we could
> not
> overcome otherwise). Before the reboot, I "umount" the proper partition and
> then "sync".
>
> For some reason, on one machine we see that the data is not updated and the
> original data is kept in the file. I konw empirically that if I add a
> "sleep(5)" after the umount, and before the "reboot" the data is written to
> the disk.
>
Disk write cache without battery backup is the first thing that comes to
mind.
Check your disk's specifications and how to control the cache.
> Any tips how to debug this?
> * the system is a TI 2.6.32 kernel (OMAP)
> * the data is saved using fopen()
> * disk is umounted using system("umount /data"), and then I call from C to
> sync();
>
Why not a direct umount(2) call?
--Amos
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