Messages in this thread | | | Date | Sun, 9 Aug 2020 20:42:51 +0200 | From | "Ahmed S. Darwish" <> | Subject | Re: [PATCH v4 08/24] seqlock: lockdep assert non-preemptibility on seqcount_t write |
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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 https://lkml.kernel.org/r/20200720155530.1173732-10-a.darwish@linutronix.de/
with the problematic "lockdep_assert_preemption_disabled()" removed?
> Guenter >
Thanks,
-- Ahmed S. Darwish Linutronix GmbH
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