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From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	linux-kernel@vger.kernel.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Masami Hiramatsu <mhiramat@kernel.org>
Subject: Re: [RFC][PATCH 0/5] perf/tracing/cpuhotplug: Fix locking order
Date: Sat, 13 May 2017 06:40:03 -0700	[thread overview]
Message-ID: <20170513134003.GA30927@linux.vnet.ibm.com> (raw)
In-Reply-To: <20170512173448.5e2106b6@gandalf.local.home>

On Fri, May 12, 2017 at 05:34:48PM -0400, Steven Rostedt wrote:
> On Fri, 12 May 2017 21:49:56 +0200

[ . . . ]

> This means that text_mutex, which was taken by the alternative code, no
> longer is taken in cpu hotplug code. That means there's no longer a
> deadlock scenario, as we don't have anyplace(*) that grabs
> get_online_cpus() and takes the text_mutex. Removing that will
> simplify things tremendously!
> 
> (*) with one exception: perf.
> 
> Currently perf does a get_online_cpu() at a high level. Will it be
> possible to move that down, such that we don't have it taken when we do
> any software events?

Can perf get rid of get_online_cpus(), perhaps using the mutexes acquired
by perf_event_init_cpu() or by perf_event_exit_cpu()?

							Thanx, Paul

  reply	other threads:[~2017-05-13 13:40 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
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 [this message]
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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