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Message-ID: <CACT4Y+aiwqvjzhWgpYpSWSRmOCZUq9ui73q0tvPRHb5z8YqVGA@mail.gmail.com>
Date: Fri, 29 Jan 2016 14:16:12 +0100
From: Dmitry Vyukov <dvyukov@...gle.com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: Oleg Nesterov <oleg@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Richard Weinberger <richard@....at>,
"Amanieu d'Antras" <amanieu@...il.com>,
Chris Metcalf <cmetcalf@...hip.com>,
Andy Lutomirski <luto@...capital.net>,
Davidlohr Bueso <dave@...olabs.net>,
Vladimir Davydov <vdavydov@...allels.com>,
Palmer Dabbelt <palmer@...belt.com>,
LKML <linux-kernel@...r.kernel.org>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>
Subject: Re: WARNING in set_restore_sigmask
On Fri, Jan 29, 2016 at 12:53 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> Dmitry,
>
> On Fri, 29 Jan 2016, Dmitry Vyukov wrote:
>> WARNING: CPU: 2 PID: 10905 at ./arch/x86/include/asm/thread_info.h:236
>> sigsuspend+0x18e/0x1f0()
>> Modules linked in:
>> CPU: 2 PID: 10905 Comm: syz-executor Not tainted 4.5.0-rc1+ #300
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>> 00000000ffffffff ffff88006139fe38 ffffffff82be118d 0000000000000000
>> ffff88006d054740 ffffffff867387e0 ffff88006139fe78 ffffffff813536d9
>> ffffffff813839ce ffffffff867387e0 00000000000000ec 0000000020000000
>> Call Trace:
>> [< inline >] __dump_stack lib/dump_stack.c:15
>> [<ffffffff82be118d>] dump_stack+0x6f/0xa2 lib/dump_stack.c:50
>> [<ffffffff813536d9>] warn_slowpath_common+0xd9/0x140 kernel/panic.c:482
>> [<ffffffff81353909>] warn_slowpath_null+0x29/0x30 kernel/panic.c:515
>> [< inline >] set_restore_sigmask
>> ./arch/x86/include/asm/thread_info.h:236
>> [<ffffffff813839ce>] sigsuspend+0x18e/0x1f0 kernel/signal.c:3513
>> [< inline >] SYSC_rt_sigsuspend kernel/signal.c:3533
>> [<ffffffff81387d7c>] SyS_rt_sigsuspend+0xac/0xe0 kernel/signal.c:3523
>> [<ffffffff86653236>] entry_SYSCALL_64_fastpath+0x16/0x7a
>> arch/x86/entry/entry_64.S:185
>> ---[ end trace da5c27e3b7defd96 ]---
>
> That could be just a spurious wakeup of unknown provenience. The sigsuspend
> code has no protection against those. I can't see why that happens ...
You mean that you _see_ why this warning happens?
>
>> Unfortunately I cannot reproduce it. But the only two programs that
>
> I would be helpful if you could run your fuzzers with a minimal set of trace
> points enabled (raw_syscalls, sched events) and set
> /proc/sys/kernel/traceoff_on_warning to 1, so the trace freezes when a warning
> is triggered.
>
> That might give us at least some insight into these one off issues.
Can you please give more concrete instructions? I never used
tracepoints. What configs do I need to enable? What runtime setup? etc
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