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From: "Chris Harrer" <cjharrer@comcast.net>
To: "'John Baldwin'" <jhb@freebsd.org>
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Date: Wed, 29 Jul 2009 14:02:30 -0400
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Cc: freebsd-drivers@freebsd.org
Subject: RE: Driver development question
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>The problem is that kernel threads do not have a valid file descriptor
table, 
>hence fd_cdir is NULL.  You could work around this if you create a
dedicated 
>kproc and set fd_cdir to rootvnode (but vref() rootvnode when you do this).

>You should also set fd_rdir and fd_jdir to rootvnode as well (also doing 
>appropriate vref() of rootvnode for each reference).  Something like this:
>
>	struct filedesc *fdp;
>
>	fdp = curthread->td_proc->p_fd;
>	FILEDESC_XLOCK(fdp);
>	fd->fd_rdir = rootvnode;
>	vref(rootvnode);
>	fd->fd_jdir = rootvnode;
>	vref(rootvnode);
>	fd->fd_cdir = rootvnode;
>	vref(rootvnode);
>	FILEDESC_XUNLOCK(fdp);
>
>You should not do this from a callout routine or interrupt handler however.

>You could do this via a TASK to a private taskqueue with a dedicated kernel

>process however.  (i.e. queue a task that does the above during after 
>creating the taskqueue and then queue a task to create the file later).
>
>-- 
>John Baldwin

John,

Thanks so much for the help and quick response, I will try this now.

Cheers,

Chris