Re: RFA: Fix lin-lwp SIGINT handling for 2.6

[Michael Snyder <msnyder@redhat.com>]

Daniel Jacobowitz wrote:
> This patch fixes a number of inconsistent regressions in schedlock.exp and
> pthreads.exp on 2.6-series kernels, using LinuxThreads.  Red Hat 2.4 kernels
> have the same problems; the fix will work there too iff there is an update
> which exports ShdPnd in /proc.
> 
> The problem is that the SIGINT is delivered to every thread, and not
> properly flushed.  So we go later to step or continue and get an "echo" of
> the original SIGINT.  This is a timing problem caused by the introduction of
> two signal queues in the kernel; the SIGSTOP is now guaranteed to be
> delivered before the SIGINT, since it's on the thread-specific queue.  It
> used to be that SIGINT would be delivered first; they were on the same
> queue, and SIGINT was lower numbered.
> 
> So we have to check whether a SIGINT is pending (and not blocked/ignored)
> for the current thread after we stop it, and resume the thread to catch the
> SIGINT if so.
> 
> It's not a perfect fix, but it's enough more reliable than the current
> scheme that I haven't been able to reproduce the problems.  OK?  HEAD only;
> this is a bit of an annoyance, but too risky for the branch, IMO.
> 

I've been worried about that.

May I suggest that the function that opens a proc file belongs
in linux-proc.c?