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Date: Wed, 28 Apr 2010 11:56:44 -0700
From: Richard Henderson <rth@twiddle.net>
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Subject: Re: [Qemu-devel] NPTL user mode fixes
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To: David Munday <cromom@soe.ucsc.edu>
Cc: qemu-devel@nongnu.org

On 04/26/2010 04:00 PM, David Munday wrote:
> I starting to work with qemu to enable NPTL dependent binaries to run in
> user mode. I see that currently NPTL is not supported for SPARC or x86.
> 
> What is still left to do for NPTL support?

The thing that's missing to enable the compile with NPTL is cpu_set_tls.
For Sparc I believe this is merely an assignment to %g7.  For x86, you
need to arrange for a call to do_set_thread_area, which is currently
private to linux-user/syscall.c.

However, the other thing that will need to be fixed is that neither port
implements its atomic operations atomically -- the implementations merely
assume that only one thread is active.  See do_store_exclusive in
linux-user/main.c for how several ports handle their atomic operations.
It'll be a bit different for Sparc singe it has LDSTUB and SWAP as well
as CAS.  It'll be lots different for x86, since quite a few read-modify-write
operations can be made atomic by use of the LOCK prefix (this could be 
quite an undertaking, actually).


r~