Re: clone_cleanup() doesn't

On Fri, Aug 14, 2009 at 03:23:57PM -0400, Andrew Gallatin wrote:
> Robert Watson wrote:
> >On Fri, 14 Aug 2009, Andrew Gallatin wrote:
> >
> >>I've been porting a closed-source driver to FreeBSD 8 from FreeBSD 
> >>5/6/7. It use the dev_clone() eventhandler to mimic linux-like open 
> >>semantics (for linux binary compat).
> >
> >No particular experience with unloading cloning stuff, but have you 
> >noticed that in 8.x we now have per-file descriptor device state?  This 
> >is often the semantics people actually want, rather than cloning.  See 
> >devfs_set_cdevpriv(9) for details -- there are several synthetic devices 
> >in the tree that use it now (although some of them do too much 
> >error-checking, and should assert rather than return errors, I think).
> 
> Unfortunately, I think I still need device cloning.  The linux semantics
> are to open /dev/mx0, then call an ioctl to set the device private
> state.  This gets set (in linux) in the "struct file *" ->private_data
> field.  So multiple processes can open /dev/mx0, and they all have
> different private data.
This is exactly what you get with cdevpriv. You open a single device
node, and driver attaches a private data to the file descriptor.

> 
> FWIW:
> 
> >>I'm assuming these files are lingering because clone_cleanup()
> >>(called at device detach) is not cleaning up these lingering
> >>device nodes.  I've tried writing a dtrace script to trace
> >>clone_cleanup.  But since that happens from device detach,
> >>dtrace doesn't work (blocks driver unload).  I've also tried
> >>setting a breakpoint in ddb(), but the breakpoint seems to
> >>be ignored (other breakpoints work fine, which is odd).
> 
> I think ddb wasn't working because my kernel sources didn't quite
> match my running kernel.  After a kernel & module rebuild, I can watch
> clone_cleanup(), and I see destroy_devl() get called.
> It calls devfs_destroy(), as well.
> 
> The interesting thing is that if I run devd -D -d, and watch the
> events scroll by, I see the destruction of a device with a
> null name.  Eg:
> 
> Processing event '!system=DEVFS subsystem=CDEV type=DESTROY cdev='
> Pushing table
> setting system=DEVFS
> setting subsystem=CDEV
> setting type=DESTROY
> setting cdev=
> Processing notify event
> <...>
> 
> If I do the same thing on 7.2, I see:
> 
> Processing event '!system=DEVFS subsystem=CDEV type=DESTROY cdev=mx_fake.0'
> Pushing table
> setting system=DEVFS
> setting subsystem=CDEV
> setting type=DESTROY
> setting cdev=mx_fake.0
> Processing notify event
> 
> So I wonder if the node is not getting removed because its
> name has gotten mangled somehow...
> 
> Drew
> _______________________________________________
> freebsd-current_at_freebsd.org mailing list
> http://lists.freebsd.org/mailman/listinfo/freebsd-current
> To unsubscribe, send any mail to "freebsd-current-unsubscribe_at_freebsd.org"