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Bug#758115: Disabled wait state X'32EE' on IPL of zIPL



On Sun, 24 Aug 2014 20:43:30 +0200
Bastian Blank <waldi@debian.org> wrote:

> On Sun, Aug 24, 2014 at 08:34:45PM +0200, Bastian Blank wrote:
> > On Sun, Aug 24, 2014 at 08:05:45PM +0200, Bastian Blank wrote:
> > > On Fri, Aug 22, 2014 at 07:21:31PM -0400, Stephen Powell wrote:
> > > >     32ea:       a7 f4 00 01             j       32ec <sclp_wait_for_int+0x84>
> > > >     32ee:       07 07                   nopr    %r7
> > > gcc 4.9 decides that this must never happen and adds a trap in this
> > > location, so this a is deliberate way to stop the process.
> > I found the culprit: The tree-isolate-paths pass in gcc 4.9.  If I
> > disable this pass I get:
> 
> And -fno-delete-null-pointer-checks seems to be the correct option.

From the gcc man page:

-fdelete-null-pointer-checks
 Use global dataflow analysis to identify and eliminate useless checks for null pointers.  The
 compiler assumes that dereferencing a null pointer would have halted the program.  If a pointer is
 checked after it has already been dereferenced, it cannot be null.

 In some environments, this assumption is not true, and programs can safely dereference null
 pointers.  Use -fno-delete-null-pointer-checks to disable this optimization for programs which
 depend on that behavior.

So we should add this Option to CFLAGS in zipl/boot/Makefile?
Why we have not seen this problem under RHEL and SLES up to now?

Best Regards,
Michael


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