Martin, sorry for delay, On 01/07, Martin Schwidefsky wrote: > > On Wed, 6 Jan 2010 13:13:29 -0800 (PST) > Roland McGrath <rol...@redhat.com> wrote: > > > > However, with or without CONFIG_UTRACE, > > > 6580807da14c423f0d0a708108e6df6ebc8bc83d > > > is needed on s390 too, otherwise the child gets unnecessary traps. > > > > This confuses me. user_disable_single_step on non-current doesn't do > > anything not already done by the memset in copy_thread. Ooh, except > > perhaps it does not clear PSW_MASK_PER. Maybe that matters. That's > > the only thing I can think of. Maybe Martin can make sense of it.
I am confused as well. Yes, I thought about regs->psw.mask change too, but I don't understand why it helps.. > The additional traps should not happen anymore with this patch: > -- > Subject: [PATCH] clear TIF_SINGLE_STEP for new process. > > From: Martin Schwidefsky <schwidef...@de.ibm.com> > > Clear the TIF_SINGLE_STEP bit in copy_thread. If the new process is > not auto-attached by the tracer it is wrong to delivere SIGTRAP to > the new process. > > Signed-off-by: Martin Schwidefsky <schwidef...@de.ibm.com> > --- > > arch/s390/kernel/process.c | 1 + > 1 file changed, 1 insertion(+) > > diff -urpN linux-2.6/arch/s390/kernel/process.c > linux-2.6-patched/arch/s390/kernel/process.c > --- linux-2.6/arch/s390/kernel/process.c 2009-12-03 04:51:21.000000000 > +0100 > +++ linux-2.6-patched/arch/s390/kernel/process.c 2010-01-07 > 09:25:53.000000000 +0100 > @@ -217,6 +217,7 @@ int copy_thread(unsigned long clone_flag > p->thread.mm_segment = get_fs(); > /* Don't copy debug registers */ > memset(&p->thread.per_info, 0, sizeof(p->thread.per_info)); > + clear_tsk_thread_flag(p, TIF_SINGLE_STEP); Even if I don't understand s390, I think this patch makes sense anyway. Or, user_disable_single_step() can clear this bit. But. Acoording to the testing I did (unless I did something wrong again) this patch doesn't make any difference in this particular case. 6580807da14c423f0d0a708108e6df6ebc8bc83d does. And. Please note that the test-case triggers 799 "false step", but TIF_SINGLE_STEP is surely cleared (by the caller) after the first invocation of do_single_step(). Oleg.
