broken device locking, sg vs. sg_io on block devices

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From: Eduard Bloch
Date: Friday, March 30, 2007 - 4:17 am

Hello,

I am talking this issue to LKML now.

Short story: using O_EXCL on /dev/srX alone does not help to prevent
other process from killing your burn process by just reading the
/dev/sgX device associated with yours, and vice versa. We have done the
best we could to make safe operation (in contrary to Schilling's
kill-this-evil-hald-thing bitching) but that is not enough, the locking
has to be established on kernel layer.

Long story:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=413960
https://bugzilla.novell.com/show_bug.cgi?id=226019
http://lists.alioth.debian.org/pipermail/debburn-devel/2007-February/000297.html
and other error messages.

There is AFAICS no simple way to establish locking across the driver
borders. If kernel developers have a good idea, any help is appreciated.

Below are the typical symptoms: wodim operates via /dev/sgX because the
user chosen it this way, some other process (most likely hald) comes
along and reads from /dev/sr0 and the drive gets confused. Boom.

Regards,
Eduard.

* Gerald Lutter [Mon, Mar 26 2007, 06:10:44PM]:
                                       ^^^^^^^^^
...
Track 01:    0 of  692 MB written.
...


-- 
* Amaya knuddelt Ganneff because of his email to private :*
<Ganneff> ich wusst doch dass die irgendwo was schlechtes nach sich zieht.
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Messages in current thread:
broken device locking, sg vs. sg_io on block devices, Eduard Bloch, (Fri Mar 30, 4:17 am)
Re: broken device locking, sg vs. sg_io on block devices, Christoph Hellwig, (Fri Mar 30, 6:43 am)
Re: broken device locking, sg vs. sg_io on block devices, Jan Engelhardt, (Fri Mar 30, 12:09 pm)
Re: broken device locking, sg vs. sg_io on block devices, Eduard Bloch, (Sat Mar 31, 10:07 am)