On Thu, Feb 04, 2010 at 03:40:28PM -0500, Andrew Gallatin wrote: > I've got a commercial driver that uses device cloning. > At unload time, the driver calls clone_cleanup(). When I unload > the driver when the kernel is built with INVARIANTS, I'll see a > panic in devfs_populate_loop(). This happens in 6-stable, > as well as 8-stable. > > From what I can see the clone has been freed, but it > remains on the devfs cdevp_list. Then the next time > devfs_populate_loop() is called, it trips over the bad > entry (cdp->cdp_dirents points to 0xdeadc0dedeadc0de) > See appended kgdb session. > > If I trace the code path, it looks like clone_cleanup() > calls destroy_devl(). And destroy_devl() will eventually > call devfs_free() if the si_refcnt is zero. But I don't > see anything which will get the cdev removed from > the cdevp_list prior to it being freed. > > The only code I see which will get the cdev removed from > the cdevp_list() seems to be the "GC any lingering devices" > block in devfs_populate_loop > > What am I missing?
You did not mentioned it, but my guess is that you create clones from the dev_clone event handler. Please note that devfs_lookup() that fires dev_clone event, consumes a device reference. Thus clone handlers shall do dev_ref(). Due to races with cleanup, you should use MAKEDEV_REF flag for make_dev_credv(9) KPI instead of doing make_dev()/dev_ref() pair. That said, do you really need clones at all ?
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