linux-kernel - Re: [RFC][PATCH 0/5] perf/tracing/cpuhotplug: Fix locking order

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

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