Date: Wed, 29 Jul 2009 15:39:05 -0400 From: "Chris Harrer" <cjharrer@comcast.net> To: "'Chris Harrer'" <cjharrer@comcast.net>, "'John Baldwin'" <jhb@freebsd.org> Cc: freebsd-drivers@freebsd.org Subject: RE: Driver development question Message-ID: <000f01ca1084$3c20caf0$b46260d0$@net> References: <002801ca06f0$b1d42af0$157c80d0$@net> <20090725035643.GT49724@elvis.mu.org> <000c01ca1071$54991d70$fdcb5850$@net> <200907291356.51702.jhb@freebsd.org>
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Hi John,
Sorry for top posting...
I put a delay in my thread waiting for rootvnode to be set and I'm able to
create a file now.
Thanks!
Chris
-----Original Message-----
From: Chris Harrer [mailto:cjharrer@comcast.net]
Sent: Wednesday, July 29, 2009 2:51 PM
To: 'Chris Harrer'; 'John Baldwin'
Cc: 'Alfred Perlstein'; 'freebsd-drivers@freebsd.org'
Subject: RE: Driver development question
>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
Hi John,
I tried this and rootvnode = 0x0, so I am still getting a SIGSEGV. I create
a thread in my "attach" routine via:
status = kproc_create(sxg_dump_thread, adapter, &adapter->dumpproc,
RFNOWAIT , 0, "sxgdump");
if (status) {
SXG_DBG_MSG(adapter->dev, "%s[%p], Cannot create dump
thread, status: %d\n",
__func__, adapter, status);
return (status);
}
Then my thread does:
static void
sxg_dump_thread(void * arg)
{
adapter_t *adapter = (adapter_t *)arg;
struct filedesc *fdp;
ulong32 index = 0;
// Set up some file descriptor stuff so we can
// actually open/create a dump file. Kernel
// threads, by design, do not have a valid
// file descriptor table. So, we're gonna
// make this thread point to one!
fdp = curthread->td_proc->p_fd;
FILEDESC_XLOCK(fdp);
fdp->fd_rdir = rootvnode;
vref(rootvnode); <----- SIGSEGV on this line, rootvnode = 0x0
fdp->fd_jdir = rootvnode;
vref(rootvnode);
fdp->fd_cdir = rootvnode;
vref(rootvnode);
FILEDESC_XUNLOCK(fdp);
for (;;){
...
Sorry if I'm doing something obviously wrong, I'm trying to come up to speed
as quickly as I can.
Cheers,
Chris
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