Shells hang during script execution

[Christopher Faylor]

On Thu, Feb 23, 2006 at 04:33:45PM -0500, Ernie Coskrey wrote:
>There are two hang conditions that we've identified and have developed fixes for.  This is a description of the first of the two along with a patch; I'll follow up with a description and patch for the second.
>
>
>If a signal can't be handled because it is blocked, it gets queued (on 
>the process's "sigq") to be handled later. Now, whenever the process's 
>signal mask changes (e.g., the signal in question gets unblocked), an 
>attempt is made to handle all the queued signals (i.e., a signal flush 
>occurs). However, if the queueing of the blocked signal happens right 
>after the signal mask change, then we miss the signal. This causes the 
>process to hang. The signal is on the queue, but the process doesn't 
>know to check for it. The process just hangs until another signal gets 
>sent to it.
>
>The workaround is basically to force the signal queue to be rescanned 
>(flushed) whenever we add something to it, so a queued signal is never 
>missed.

Thanks for the analysis and the patch.

But, a backwards goto into a case?  Yuck.  I'll see if I can come up
with something better.

cgf

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