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From: Steven Rostedt <rostedt@goodmis.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Masami Hiramatsu <mhiramat@kernel.org>
Subject: Re: [RFC][PATCH 2/5] cpu-hotplug: Allow get_online_cpus() to nest
Date: Fri, 12 May 2017 20:23:16 -0400	[thread overview]
Message-ID: <20170512202316.49df3548@gandalf.local.home> (raw)
In-Reply-To: <alpine.DEB.2.20.1705130013210.2340@nanos>

On Sat, 13 May 2017 00:15:03 +0200 (CEST)
Thomas Gleixner <tglx@linutronix.de> wrote:

> 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 ....
> 

After I sent the updated changes to Paul, I realized this. But didn't
update it as I turned my attention to seeing if we can still get it
done without it.

But I'm not convinced that we can yet. I'll reply to Peter's email
again later.

-- Steve

  reply	other threads:[~2017-05-13  0:23 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-12 17:15 [RFC][PATCH 0/5] perf/tracing/cpuhotplug: Fix locking order Steven Rostedt
2017-05-12 17:15 ` [RFC][PATCH 1/5] tracing: Make sure RCU is watching before calling a stack trace Steven Rostedt
2017-05-12 18:25   ` Paul E. McKenney
2017-05-12 18:36     ` Steven Rostedt
2017-05-12 18:50       ` Paul E. McKenney
2017-05-12 20:05         ` Steven Rostedt
2017-05-12 20:31           ` Paul E. McKenney
2017-05-17 16:46             ` Steven Rostedt
2017-05-12 17:15 ` [RFC][PATCH 2/5] cpu-hotplug: Allow get_online_cpus() to nest Steven Rostedt
2017-05-12 18:35   ` Paul E. McKenney
2017-05-12 18:40     ` Steven Rostedt
2017-05-12 18:52       ` Paul E. McKenney
2017-05-12 22:15   ` Thomas Gleixner
2017-05-13  0:23     ` Steven Rostedt [this message]
2017-05-12 17:15 ` [RFC][PATCH 3/5] kprobes: Take get_online_cpus() before taking jump_label_lock() Steven Rostedt
2017-05-12 18:39   ` Paul E. McKenney
2017-05-12 18:44     ` Steven Rostedt
2017-05-17 17:50   ` Masami Hiramatsu
2017-05-12 17:15 ` [RFC][PATCH 4/5] tracepoints: Grab get_online_cpus() before taking tracepoints_mutex Steven Rostedt
2017-05-12 17:15 ` [RFC][PATCH 5/5] perf: Grab event_mutex before taking get_online_cpus() Steven Rostedt
2017-05-12 18:13 ` [RFC][PATCH 0/5] perf/tracing/cpuhotplug: Fix locking order Paul E. McKenney
2017-05-12 19:49 ` Peter Zijlstra
2017-05-12 20:14   ` Steven Rostedt
2017-05-12 21:34   ` Steven Rostedt
2017-05-13 13:40     ` Paul E. McKenney
2017-05-15  9:03       ` Peter Zijlstra
2017-05-15 18:40         ` Paul E. McKenney
2017-05-16  8:19           ` Peter Zijlstra
2017-05-16 12:46             ` Paul E. McKenney
2017-05-16 14:27               ` Paul E. McKenney
2017-05-17 10:40                 ` Peter Zijlstra
2017-05-17 14:55                   ` Paul E. McKenney
2017-05-18  3:58                     ` Paul E. McKenney
2017-05-15 19:06   ` Steven Rostedt

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