Re: [patch V2 24/24] cpu/hotplug: Convert hotplug locking to percpu rwsem

From	Michael Ellerman <mpe@ellerman.id.au>
Newsgroups	linux.kernel
Subject	Re: [patch V2 24/24] cpu/hotplug: Convert hotplug locking to percpu rwsem
Date	2017-05-11 07:50 +0200
Message-ID	<tFP97-2ex-1@gated-at.bofh.it> (permalink)
References	<txHip-1Gh-3@gated-at.bofh.it> <txHs6-1Kl-11@gated-at.bofh.it> <tFs2R-4Nw-3@gated-at.bofh.it> <tFvtL-6TH-1@gated-at.bofh.it>
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Thomas Gleixner <tglx@linutronix.de> writes:

> On Wed, 10 May 2017, Michael Ellerman wrote:
>
>> Thomas Gleixner <tglx@linutronix.de> writes:
>> 
>> > @@ -130,6 +130,7 @@ void __static_key_slow_inc(struct static
>> >  	 * the all CPUs, for that to be serialized against CPU hot-plug
>> >  	 * we need to avoid CPUs coming online.
>> >  	 */
>> > +	lockdep_assert_hotplug_held();
>> >  	jump_label_lock();
>> >  	if (atomic_read(&key->enabled) == 0) {
>> >  		atomic_set(&key->enabled, -1);
>> 
>> I seem to be hitting this assert from the ftrace event selftests,
>> enabled at boot with CONFIG_FTRACE_STARTUP_TEST=y, using next-20170509
>> (on powerpc).
>> 
>> The stupidly obvious (or perhaps obviously stupid) patch below fixes it:
>
> Kinda. There is more horror in that area lurking and I'm still trying to
> figure out all the convoluted call pathes.

OK thanks.

cheers

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Re: [patch V2 24/24] cpu/hotplug: Convert hotplug locking to percpu rwsem Michael Ellerman <mpe@ellerman.id.au> - 2017-05-10 07:10 +0200
  Re: [patch V2 24/24] cpu/hotplug: Convert hotplug locking to percpu  rwsem Thomas Gleixner <tglx@linutronix.de> - 2017-05-10 10:50 +0200
    Re: [patch V2 24/24] cpu/hotplug: Convert hotplug locking to percpu  rwsem Steven Rostedt <rostedt@goodmis.org> - 2017-05-10 18:40 +0200
      Re: [patch V2 24/24] cpu/hotplug: Convert hotplug locking to percpu  rwsem Steven Rostedt <rostedt@goodmis.org> - 2017-05-10 19:20 +0200
    Re: [patch V2 24/24] cpu/hotplug: Convert hotplug locking to percpu rwsem Michael Ellerman <mpe@ellerman.id.au> - 2017-05-11 07:50 +0200

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