lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Sun, 9 Aug 2020 20:42:51 +0200
From:   "Ahmed S. Darwish" <>
To:     Guenter Roeck <>
Cc:     Peter Zijlstra <>,
        Ingo Molnar <>, Will Deacon <>,
        Thomas Gleixner <>,
        "Paul E. McKenney" <>,
        "Sebastian A. Siewior" <>,
        Steven Rostedt <>,
        LKML <>
Subject: Re: [PATCH v4 08/24] seqlock: lockdep assert non-preemptibility on
 seqcount_t write

On Sat, Aug 08, 2020 at 04:21:22PM -0700, Guenter Roeck wrote:
> On Mon, Jul 20, 2020 at 05:55:14PM +0200, Ahmed S. Darwish wrote:
> > Preemption must be disabled before entering a sequence count write side
> > critical section.  Failing to do so, the seqcount read side can preempt
> > the write side section and spin for the entire scheduler tick.  If that
> > reader belongs to a real-time scheduling class, it can spin forever and
> > the kernel will livelock.
> >
> > Assert through lockdep that preemption is disabled for seqcount writers.
> >
> This patch is causing compile failures for various images (eg arm:allmodconfig,
> arm:imx_v6_v7_defconfig, mips:allmodconfig).
> In file included from arch/arm/include/asm/bug.h:60,
>                  from include/linux/bug.h:5,
>                  from include/linux/thread_info.h:12,
>                  from include/asm-generic/current.h:5,
>                  from ./arch/arm/include/generated/asm/current.h:1,
>                  from include/linux/sched.h:12,
>                  from arch/arm/kernel/asm-offsets.c:11:
> include/linux/seqlock.h: In function 'write_seqcount_begin_nested':
> include/asm-generic/percpu.h:31:40: error: implicit declaration of function 'raw_smp_processor_id'
> Reverting it fixes the problem. Is this being addressed ?

@Peter, I think let's revert this one for now?

Shall I also send you a version of:

    [PATCH v4 09/24] seqlock: Extend seqcount API with associated locks

with the problematic "lockdep_assert_preemption_disabled()" removed?

> Guenter


Ahmed S. Darwish
Linutronix GmbH

Powered by blists - more mailing lists