[Openmcl-devel] [openmcl-devel] Throw "Thread Safe?"

[David L. Rager]

This answers my question exactly.  Thanks!

> -----Original Message-----
> From: Gary Byers [mailto:gb at clozure.com]
> Sent: Wednesday, January 24, 2007 4:07 PM
> To: David L. Rager
> Cc: openmcl-devel at clozure.com
> Subject: Re: [Openmcl-devel] [openmcl-devel] Throw "Thread Safe?"
> 
> In the 1.1 prereleases: yes, interrupts are disabled in unwind-protect
> cleanup forms and in any stack-unwinding code between the point of
> the THROW and the corresponding CATCH target.  If interrupts were
> enabled at the time that the CATCH was established, then any interrupt
> that had been deferred during unwinding will be taken just before
> the transfer to CATCH target (after all of that unwinding is complete.)
> 
> If an UNWIND-PROTECT cleanup form actually does something that needs
> to be interruptible, it's necessary to use WITH-INTERRUPTS-ENABLED.
> (This actually happens somewhere in the code which waits for external
> processes to complete; some of that waiting occurred within an
> unwind-protect cleanup, and interrupts needed to be explicitly enabled
> in that case in order to make the wait interruptible.)
> 
> Note that (WITHOUT-INTERRUPTS (THROW ...)) wouldn't have the intended
> effect, since the THROW would cause execution to exit the extent of
> the WITHOUT-INTERRUPTS.
> 
> Prior to 1.1, interrupts could occur at arbitrary times during the
> process of unwinding the stack and executing intervening cleanup
> forms.
> 
> On Wed, 24 Jan 2007, David L. Rager wrote:
> 
> > Hello,
> >
> > Are interrupts enabled while executing a throw?
> >
> >
> > Supposed I have thread A, and it is in the middle of executing
> >
> > (throw :my-tag)
> >
> > Then suppose before A finishes the throw that thread B attempts to
> interrupt
> > thread A, where thread B executes
> >
> > (ccl:process-interrupt *A* (lambda () (throw :my-tag nil)))
> >
> >
> > Should I wrap a (without-interrupts ...) around (throw :my-tag) or is
> this issue
> > already addressed by OpenMCL?
> >
> >
> > Thank you,
> > David
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> >