linux-kernel - Re: WARN_ON_ONCE(!new_owner) within wake_futex

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Date:   Wed, 23 Jan 2019 13:40:47 +0100
From:   Heiko Carstens <heiko.carstens@...ibm.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        Stefan Liebler <stli@...ux.ibm.com>
Subject: Re: WARN_ON_ONCE(!new_owner) within wake_futex_pi() triggered

On Wed, Jan 23, 2019 at 01:33:15PM +0100, Thomas Gleixner wrote:
> Heiko,
> 
> On Wed, 23 Jan 2019, Heiko Carstens wrote:
> > It doesn't look like it does. One occurrence was the one below when
> > using commit 7939f8beecf1 (which is post 5.0-rc2) for building the
> > kernel:
> >
> >  WARNING: CPU: 14 PID: 23505 at kernel/futex.c:1483 do_futex+0xa9a/0xc50
> >  Kernel panic - not syncing: panic_on_warn set ...
> >  CPU: 14 PID: 23505 Comm: ld.so.1 Not tainted 5.0.0-20190116.rc2.git0.7939f8beecf1.300.fc29.s390x+git #1
> >  Hardware name: IBM 3906 M04 704 (LPAR)
> >  Call Trace:
> >  ([<0000000000112e60>] show_stack+0x58/0x70)
> >   [<0000000000a671fa>] dump_stack+0x7a/0xa8
> >   [<0000000000143f52>] panic+0x11a/0x2d0
> >   [<0000000000143db0>] __warn+0xf8/0x118
> >   [<0000000000a662f8>] report_bug+0xd8/0x150
> >   [<00000000001014ac>] do_report_trap+0xc4/0xe0
> >   [<0000000000101680>] illegal_op+0x138/0x150
> >   [<0000000000a87270>] pgm_check_handler+0x1c8/0x220
> >   [<00000000001e9aea>] do_futex+0xa9a/0xc50
> >  ([<00000000001e9c4e>] do_futex+0xbfe/0xc50)
> >   [<00000000001ea13c>] compat_sys_futex+0xe4/0x170
> >   [<0000000000a86e84>] system_call+0xd8/0x2c8 
> 
> Ok. That's another one which I can't spot yet.
> 
>     Is that only on S390?
>     What's the test which explodes? Kernel build?

No, it's the tst-robustpi8 glibc 2.28 selftest. Let me quote myself
from earlier in this thread:

"
... tst-robustpi8

And indeed, if I run only this test case in an endless loop and do
some parallel work (like kernel compile) it currently seems to be
possible to reproduce the warning:

while true; do time ./testrun.sh nptl/tst-robustpi8 --direct ; done

within the build directory of glibc (2.28).

See
https://sourceware.org/git/?p=glibc.git;a=blob;f=nptl/tst-robustpi8.c;h=cbea3d6d77abb00be05ec7b466d8339c26dd2efb;hb=3c03baca37fdcb52c3881e653ca392bba7a99c2b

which includes this one:

https://sourceware.org/git/?p=glibc.git;a=blob;f=nptl/tst-robust8.c;h=9c636250d4cb0bcd6d802910e8f9ea31568bb73f;hb=3c03baca37fdcb52c3881e653ca392bba7a99c2b
"