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Re: [RFC][PATCH 2/5] cpu-hotplug: Allow get_online_cpus() to nest

From Thomas Gleixner <tglx@linutronix.de>
Newsgroups linux.kernel
Subject Re: [RFC][PATCH 2/5] cpu-hotplug: Allow get_online_cpus() to nest
Date 2017-05-13 00:20 +0200
Message-ID <tGr4K-2RP-11@gated-at.bofh.it> (permalink)
References <tGmy5-7Uc-3@gated-at.bofh.it> <tGmy5-7Uc-1@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Fri, 12 May 2017, Steven Rostedt wrote:
>  void get_online_cpus(void)
>  {
> +#ifdef CONFIG_LOCKDEP
> +	if (current->goc_depth++)
> +		return;

This must be unconditional and not depend on lockdep. The percpu rwsem is
going to deadlock silently otherwise when a writer is waiting ....

Thanks,

	tglx

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Thread

[RFC][PATCH 2/5] cpu-hotplug: Allow get_online_cpus() to nest Steven Rostedt <rostedt@goodmis.org> - 2017-05-12 19:30 +0200
  Re: [RFC][PATCH 2/5] cpu-hotplug: Allow get_online_cpus() to nest "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-12 20:40 +0200
    Re: [RFC][PATCH 2/5] cpu-hotplug: Allow get_online_cpus() to nest Steven Rostedt <rostedt@goodmis.org> - 2017-05-12 20:50 +0200
      Re: [RFC][PATCH 2/5] cpu-hotplug: Allow get_online_cpus() to nest "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-12 21:00 +0200
  Re: [RFC][PATCH 2/5] cpu-hotplug: Allow get_online_cpus() to nest Thomas Gleixner <tglx@linutronix.de> - 2017-05-13 00:20 +0200
    Re: [RFC][PATCH 2/5] cpu-hotplug: Allow get_online_cpus() to nest Steven Rostedt <rostedt@goodmis.org> - 2017-05-13 02:30 +0200

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