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Date: Fri, 24 Feb 2006 15:22:05 -0500
From: Paul Clements <paul DOT clements AT steeleye DOT com>
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CC: ernie DOT coskrey AT steeleye DOT com
Subject: Re: Shells hang during script execution
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On Thu, Feb 23, 2006 at 04:40:33PM -0500, Christopher Faylor wrote:

 > Actually, I spoke too soon.  I don't understand your analysis.
 > You make this statement:

 >>However, if the queueing of the blocked signal happens right after the
 >>signal mask change, then we miss the signal.

 > but I don't understand how you came to this conclusion.  If the 
signal > mask
 > changes, then the queue should be flushed -- that's what the 
__SIGFLUSH is
 > for.  So, even if something is added to the queue while the mask is 
changing,
 > the function which changes the mask should eventually call send_sig 
to > cause
 > the wait_sig thread to run the queue.

 > So, this patch would seem to be a band-aid over some other problem.


OK, I think I see what is happening now:

set_signal_mask() does indeed call sig_dispatch_pending() to do a flush 
when the signal mask changes. However, when the sigq is empty, 
sig_dispatch_pending() just returns! See:


  sig_dispatch_pending (bool fast)
  {
-if (exit_state || &_my_tls == _sig_tls || !sigq.start.next)
+if (exit_state || &_my_tls == _sig_tls)


Unfortunately, when I make this change, everything hangs. Not sure what 
the issue is there. Any ideas?

Thanks,
Paul

(please CC, I'm not on the list)


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