On Wed, 8 Jun 2016, Paul Goyette wrote:
On Tue, 7 Jun 2016, Taylor R Campbell wrote:
Date: Tue, 7 Jun 2016 18:28:11 +0800 (PHT)
From: Paul Goyette <[email protected]>
Can anyone suggest a reliable way to ensure that a device-driver module
can be _really_ safely detached?
General approach:
1. Prevent new references (e.g., devsw_detach).
2. Wait for existing references to drain (or roll back with
devsw_attach if you don't want to wait, and fail with EBUSY).
3. Unload.
Yes, of course. Thanks, I think this will work.
Well, it almost works! Just one little problem... :)
For some reason, the device's open() routine is being called twice, but
the close() routine is only called once. So every iteration leaves the
refcount with a net increment of one.
I cannot figure out why/how the open routine is called twice.
If it matters, the device in question is /dev/ipl (for ipfilter) and the
open calls are a result of
# ipf -E -f -
^D
#
Other than the introduction of a mutex-plus-refcount, there are no mods
to the original driver code.
Any hints?
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| Paul Goyette | PGP Key fingerprint: | E-mail addresses: |
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| Kernel Developer | 0786 F758 55DE 53BA 7731 | pgoyette at netbsd.org |
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