[Devel] Re: [PATCH] RFC: s390: Move get_signal_to_deliver() up in do_signal

[Martin Schwidefsky]

On Wed, 10 Feb 2010 14:40:19 -0600
"Serge E. Hallyn" <serue at us.ibm.com> wrote:

> The current placement of get_signal_to_deliver() means that
> try_to_freeze() in get_signal_to_deliver() will happen after
> regs->psw.addr, regs->svcnr, and regs->gprs[2] may have been
> mangled.  Since the app may get checkpointed while frozen and
> then restarted, this means we have to attempt a complicated
> and subtle re-calculation of the initial conditions.
> 
> If we just move the get_signal_to_deliver() above the
> immediately preceding block, we enourmously simplify the
> arch-specific checkpoint/restart code.
> 
> A full ltp run seems to show no regressions do to this move,
> though I'm not familiar enough with the entry_64.S code in
> particular to be absolutely confident.
> 
> Is this a bad idea?

I think it is a bad idea. The comment of get_signal_to_deliver tells
you that the debugger is invoked and may want to change the registers.
If the get_signal_to_deliver calls is moved then the debugger sees
the unmodified registers which is imho wrong. A comparison of the
gdb testsuite with and without the patch will tell us more.

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.

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