Re: [LTP] [PATCH] pthread_detach/4-3: workaround for segment fault

[Jan Stancek <jstancek@redhat.com>]

----- Original Message -----
> From: "Kang Kai" <Kai.Kang@windriver.com>
> To: "Jan Stancek" <jstancek@redhat.com>
> Cc: ltp-list@lists.sourceforge.net, "Zhenfeng Zhao" <Zhenfeng.Zhao@windriver.com>
> Sent: Friday, 24 August, 2012 4:46:58 AM
> Subject: Re: [LTP] [PATCH] pthread_detach/4-3: workaround for segment fault
> >> I was thinking usleep(sleep_time) that progressively increases. So
> >> it
> >> starts firing signals as quickly as it can and slows down over
> >> time.
> >> Each pthread_detach() would reset the sleep_time.
> >>
> >> As for our original issue, idea I'm playing with is:
> >>
> >> main (procA) - do_child (procB) - send_sig (thread)
> >>                                  \
> >>                                    test (thread) - threaded
> >>                                    (detached thread)
> >>
> >> - turn 'while' in test() to single 'for' loop
> >> - loop in main, fork and call do_child, wait for child to finish
> > Hi,
> >
> > attached is v1 of the idea above. I ran it 100x times on various
> > setups as root and unprivileged user.
> 
> Hi Jan,
> 
> Great!
> > Kai, would you like to give a try?
> I have test it on routerstation, x86_64(ubuntu11.10 & redhat 5.3) and
> x86(redhat 5.3) each 100+ times, and all PASS.
> 

Hi,

I'm still looking at this testcase. I have been testing v1 more on different
releases and arches and I'm hitting an issue on ppc64 RHEL6.3.

I'm getting abort from gcc_assert. The most interesting thing is that
thread, which aborts shouldn't exist, because for this scenario pthread_create
returns 1 (EPERM).

(gdb) bt
#0  0x0000008066374e50 in raise (sig=<value optimized out>) at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
#1  0x0000008066376de4 in abort () at abort.c:92
#2  0x000000806687e504 in _Unwind_SetSpColumn (context=0xfff97a0df58, outer_cfa=0xfff97a0e610, outer_ra=0x8066548904) at ../../../gcc/unwind-dw2.c:1265
#3  uw_init_context_1 (context=0xfff97a0df58, outer_cfa=0xfff97a0e610, outer_ra=0x8066548904) at ../../../gcc/unwind-dw2.c:1472
#4  0x000000806687ebe0 in _Unwind_ForcedUnwind (exc=0xfff97a0f670, stop=@0x8066560ad8: 0x8066545660 <unwind_stop>, stop_argument=0xfff97a0e880) at ../../../gcc/unwind.inc:201
#5  0x0000008066548904 in _Unwind_ForcedUnwind (exc=<value optimized out>, stop=<value optimized out>, stop_argument=<value optimized out>) at ../nptl/sysdeps/pthread/unwind-forcedunwind.c:132
#6  0x0000008066545600 in __pthread_unwind (buf=<value optimized out>) at unwind.c:130
#7  0x0000008066545bac in __do_cancel () at pthreadP.h:265
#8  __pthread_enable_asynccancel () at cancellation.c:49
#9  0x000000806653c568 in start_thread (arg=0xfff97a0f200) at pthread_create.c:289
#10 0x000000806643a32c in .__clone () from /lib64/libc-2.12.so

(gdb) frame 2
#2  0x000000806687e504 in _Unwind_SetSpColumn (context=0xfff97a0df58, outer_cfa=0xfff97a0e610, outer_ra=0x8066548904) at ../../../gcc/unwind-dw2.c:1265
1265          gcc_assert (size == sizeof(_Unwind_Word));

The arg in threaded() is not used for anything, so I passed scenario number as parameter.
(gdb) p/x ((struct pthread *) 0xfff97a0f200)->arg
$1 = 0x12

So it's thread for scenario 0x12. This scenario tries to set explicit scheduling with max
priority. When you run this as unprivileged user, pthread_create gives you EPERM.

This comment is interesting, same gcc_assert(), also power7:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52839#c10

Regards,
Jan

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