libpthread patch
Daniel Eischen
eischen at pcnet1.pcnet.com
Wed Apr 16 16:46:05 PDT 2003
On Thu, 17 Apr 2003, David Xu wrote:
>
> ----- Original Message -----
> From: "Daniel Eischen" <eischen at pcnet1.pcnet.com>
> To: "David Xu" <davidxu at freebsd.org>
> Cc: <freebsd-threads at freebsd.org>
> Sent: Thursday, April 17, 2003 5:05 AM
> Subject: Re: libpthread patch
>
>
> > There's a new patch available at:
> >
> > http://people.freebsd.org/~deischen/kse/libpthread.diffs
> >
> > This passes all the ACE tests that libc_r passes, with the
> > exception of Cached_Conn_Test.
> >
> > It also seems to work with KDE, konqueror, kwrite, kmail, etc.
> > I don't have mozilla built (and am dreading trying to), but
> > it would be interesting to see if it works with that.
> >
>
> Cool!
>
> > If no-one has any objections, I'd like to commit this
> > soon. I'll let David review and comment to it first.
> >
> > David, I didn't add critical regions to _thr_alloc() and
> > _thr_free(). I think that whenever they are used, we
> > are already in a critical region or operating on an upcall.
> >
>
> Hmm, I don't like to put malloc calling under critical section,
> it is better to put it under a lock, otherwise this would cause dead
> lock. suppose that an user thread is calling malloc(), and heap manager
> got malloc spinlock, then it does somethings and the thread is preempted
> by upcall from kernel, now UTS switches to another thread, that thread
> starts to call pthread_create, so UTS kernel enters a critical region first,
> and calls malloc, this would cause dead lock, because UTS is under critical
> region and no context switch could happen.
Hmm, I see what you mean. We could put spinlock in critical region
and that may solve the problem, but I eventually want to see spinlocks
go away and replace the very few that we have in libc with mutexes.
> Also I don't like thr_free under critical region, I think a GC thread is still
> needed to recycle zombie thread and free extra memory, UTS kernel
> should't be blocked by user thread. Despite this, I think the patch should
> be committed.
I'll work on adding the GC thread back in. I really wanted to
get rid of it so that the KSE can exit when threadcount == 0,
but now we've got to make allowances for the extra thread
in the main KSEG.
Keep looking at the patch for anything else you might see.
We still need a way to deliver signals and look for async
cancel points in CPU-bound threads. The attempt to add a
signal frame with signalcontext() doesn't seem to work
which is why it is commented out.
--
Dan Eischen
More information about the freebsd-threads
mailing list