Panic on -CURRENT after LDT changes

Joe Marcus Clarke marcus at
Mon May 28 23:46:46 UTC 2007

On Tue, 2007-05-29 at 00:53 +0200, Attilio Rao wrote:
> 2007/5/28, Attilio Rao <attilio at>:
> > Tor Egge wrote:
> > >
> > > Finally, I found that i386_ldt_grow() called smp_rendezvous() without
> > > temporarily unlocking dt_lock.  That caused a deadlock.  Adding a temporary
> > > unlock of dt_lock seems to solve the problem for me.
> >
> > Effectively, there is the need to release the dt_lock before to call
> > smp_rendezvous() beacause other threads running on other CPUs will
> > contest on this lock and it will cause a deadlock (since their
> > curthreads don't hold the lock).
> > I think that mantaining the current locking requirements for
> > i386_ldt_grow() is still good, since, for how it is used, this is the
> > lighter approach. I will add release/unrelease around smp_rendezvous() too.
> Tor,
> I've updated the patch. Can you please redownload it and test/review:

I can confirm that with this patch, an SMP i386 Tinderbox machine of
mine that was seeing Tor's "lock held too long" panic survives much
longer.  No crashes after a few port builds.


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