From: Ulrich Weigand <uweigand@de.ibm.com>
Message-Id: <200505042133.j44LX8Xk010820@53v30g15.boeblingen.de.ibm.com>
Subject: Re: Again: UML on s390 (31Bit)
To: bstroesser@fujitsu-siemens.com
Date: Wed, 4 May 2005 23:33:08 +0200 (CEST)
Cc: schwidefsky@de.ibm.com, linux-kernel@vger.kernel.org
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Bodo Stroesser wrote:

>Unfortunately, I guess this will not help. But maybe I'm missing
>something, as I don't even understand, what the effect of the
>attached patch should be.
Have you tried it?

>AFAICS, after each call to do_signal(),
>entry.S will return to user without regs->trap being checked again.
>do_signal() is the only place, where regs->trap is checked, and
>it will be called on return to user exactly once.
It will be called multiple times if *multiple* signals are pending,
and this is exactly the situation in your problem case (some other
signal is pending after the ptrace intercept SIGTRAP was delievered).

>So a practical solution should allow to reset regs->trap while the
>child is on the first or second syscall interception.
This is exactly what this patch is supposed to do: whenever during
a ptrace intercept the PSW is changed (as it presumably is by your
sigreturn implementation), regs->trap is automatically reset.

Bye,
Ulrich

-- 
  Dr. Ulrich Weigand
  Linux on zSeries Development
  Ulrich.Weigand@de.ibm.com
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