LOR: /sys/ufs/ffs/ffs_snapshot.c:1893 /sys/vm/vm_map.c:2206
Brian Fundakowski Feldman
green at FreeBSD.org
Fri Apr 30 21:12:34 PDT 2004
Robert Watson <rwatson at FreeBSD.org> wrote:
>
> On Fri, 30 Apr 2004, Brian Fundakowski Feldman wrote:
>
> > I haven't seen it myself, but it seems like it's only going to happen
> > sometimes (when a full page is freed). There's really no technical
> > reason you'd ever want to do a free(9) with locks held, so I suggest
> > fixing it in the straightforward way.
>
> While I sympathize with this point, I don't think it's realistic to assert
> that free() will never be called while helding a lock. Once the mbuf
> allocator backs into regular malloc() and free(); the network stack relies
> on being able to perform wait-free allocation and free while locks are
> held, since it uses locks as a light-weight form of reference-counting.
Well, there's locks, and then there's mutexes; the vnode interlock is a
mutex that is really, really not supposed to be slept while holding.
--
Brian Fundakowski Feldman \'[ FreeBSD ]''''''''''\
<> green at FreeBSD.org \ The Power to Serve! \
Opinions expressed are my own. \,,,,,,,,,,,,,,,,,,,,,,\
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