Re: updating COMPAT_LINUX for linux 2.6.x support.

[Andrew Doran <ad%NetBSD.org@localhost>]

On Sun, May 02, 2010 at 07:32:09PM -0700, Chuck Silvers wrote:

>     I tried following the suggestion in PR 37437 (moving the ps_sigignore
>     and ps_sigcatch fields from struct sigctx to struct sigacts, which is
>     shared between linux threads), and I moved p_sigpend from struct proc
>     to struct sigacts as well.  this, together with other fixes allows
>     all of the netbsd libpthread regression tests to pass (except the one
>     that also fails natively on linux), and gives much improved results
>     on the LTP/posixtest tests.  I put my current diff (still larded with
>     debug stuff and with linux stuff hardcoded instead of called through
>     new emul callbacks) in:
>       ftp://ftp.netbsd.org/pub/NetBSD/misc/chs/linux/diff.linux-nptl.4

I think there should be no reason for sigacts to have its own lock.
I changed things so that cloned processes share the same p->p_lock.
If you check fork1() to ensure that p->p_lock is always shared
if any kind of signal state is shared by the child, then the sigacts
lock can be removed.

>     before continuing down this path, I was wondering if it would be
>     possible to move from the current way of supporting linux threads
>     (each linux thread is a separate netbsd process, with extra sharing
>     happening behind the scenes) to the native netbsd way (1 process with
>     multiple LWPs)?  the only problem I can think of is that something
>     might assume that linux thread IDs are globally unique, or that the
>     thread ID of the original thread is the same as the process ID.
>     but that seems a bit unlikely, since I don't see any place that the
>     linux thread ID is used (thought I could easily have missed that).
>     does anyone know of any reason why this wouuldn't work?

I wish we could go back in time and undo clone(), it makes a hash of the
the process data structures.