Re: handle_threadlist_exception: handle_threadlist_exception called with threadlist_ix -1

[Pavel Tsekov <ptsekov at gmx dot net>]

On Thu, 6 Oct 2005, Pavel Tsekov wrote:

> On Thu, 6 Oct 2005, Christopher Faylor wrote:
>
> > >It might be a different problem but the message is the same.
> >
> > It *is* a different problem.
>
> Ok.
>
> > Some thread is sending a signal 31 (SIGUSR1).  Which thread is doing this?
>
> An application thread signaling another thread to stop its execution. I am
> on it - I'll report back if I manage to find something.

While tracking this problem I found what I suspect is a small bug in
the way sigsuspend() works when it is used to retrieve the list of pending
signals for a thread other than the main one. I think this is related to
the crash I am seeing in some way though this has to be determined yet.

As I read the code, when retrieving the list of pending signals
sigpending() inspects only the list of blocked signals for the main
thread - it doesn't look in the thread specific list of blocked signals
of the calling thread.

The code which I refer to is the following block from wait_sig():

        case __SIGPENDING:
          *pack.mask = 0;
          unsigned bit;
          sigq.reset ();
          while ((q = sigq.next ()))
            if (myself->getsigmask () & (bit = SIGTOMASK (q->si.si_signo)))
              *pack.mask |= bit;
          break;

On the other hand the code in sigpacket::process() does the right thing
when it delivers a signal i.e. it looks the list of blocked signals in
both the main thread and the target thread.

Attached is a simple test case which demonstrates the problem.

On Linux:

pending_set = 00000000
pending_set = 00000000
pending_set = 00000000
pending_set = 00000000
pending_set = 00000000
pending_set = 00000800
exiting thread_loop()

On Cygwin:

pending_set = 00000000
pending_set = 00000000
pending_set = 00000000
pending_set = 00000000
pending_set = 00000000
pending_set = 00000000
pending_set = 00000000
pending_set = 00000000
pending_set = 00000000
pending_set = 00000000
pending_set = 00000000
pending_set = 00000000
pending_set = 00000000

[ keeps looping forever ]

Attachment: sigpending_thr.c
Description: Text document

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