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Date: Sat, 13 May 2017 06:40:03 -0700 From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> To: Steven Rostedt <rostedt@...dmis.org> Cc: Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Masami Hiramatsu <mhiramat@...nel.org> Subject: Re: [RFC][PATCH 0/5] perf/tracing/cpuhotplug: Fix locking order 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
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