Re: [PATCH RFA] Clean up spurious SIGSTOPS in lin-lwp

[Michael Snyder <msnyder at cygnus dot com>]

Mark Kettenis wrote:
> 
>    Date: Fri, 25 May 2001 15:57:39 -0700
>    From: Michael Snyder <msnyder@cygnus.com>
> 
>    Mark,
> 
>    This patch will get rid of most of those "Delayed SIGSTOP" messages,
>    so that lin_lwp_wait will rarely if ever get a SIGSTOP that was generated
>    by gdb.  It entails three basic changes:
> 
>     * In lin_lwp_attach_lwp, consume the SIGSTOP that is generated by
>       PTHREAD_ATTACH.
>     * In stop_wait_callback, try again to consume the SIGSTOP after
>       "pushing back" a SIGTRAP for a thread other than the event thread.
>     * Similarly try again to consume a SIGSTOP after tossing away a
>       redundant SIGINT.
> 
> In principle the current approach saves us a few system calls, at the
> risk of a GDB-generated SIGSTOP colliding with a SIGSTOP that wasn't
> generated by GDB.
> 
> I assume you're trying to make GDB behave a little better when some
> outside agency is generating SIGSTOPs. 

No, I'm working on a bug, and trying to simplify parts of the
event handling in order to clear the way.  The bug that I'm really
aiming for is a scheduling issue -- gdb can cause some threads
to starve.  Don't worry, it isn't your fault, it's been in all of
the linux thread debugging implementations so far.  It causes a
couple of failures in the testcase "pthreads.exp".  I know in
principal what to do, but in practice it's proving to be tricky.

I've checked in this part of the change.

Michael