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Date: Mon, 25 Apr 2016 21:47:47 -0300
From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>,
        David Ahern <dsahern@gmail.com>, Peter Zijlstra <peterz@infradead.org>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Ingo Molnar <mingo@kernel.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Brendan Gregg <brendan.d.gregg@gmail.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Alexei Starovoitov <ast@kernel.org>, He Kuang <hekuang@huawei.com>,
        Jiri Olsa <jolsa@redhat.com>, Masami Hiramatsu <mhiramat@kernel.org>,
        Milian Wolff <milian.wolff@kdab.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Stephane Eranian <eranian@google.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vince Weaver <vincent.weaver@maine.edu>,
        Wang Nan <wangnan0@huawei.com>, Zefan Li <lizefan@huawei.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH/RFC v3] perf core: Allow setting up max frame stack depth
 via sysctl
Message-ID: <20160426004747.GC16708@kernel.org>
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Em Mon, Apr 25, 2016 at 05:44:00PM -0700, Alexei Starovoitov escreveu:
> On Mon, Apr 25, 2016 at 09:29:28PM -0300, Arnaldo Carvalho de Melo wrote:
> > Em Mon, Apr 25, 2016 at 05:07:26PM -0700, Alexei Starovoitov escreveu:
> > > > +	{
> > > > +		.procname	= "perf_event_max_stack",
> > > > +		.data		= NULL, /* filled in by handler */
> > > > +		.maxlen		= sizeof(sysctl_perf_event_max_stack),
> > > > +		.mode		= 0644,
> > > > +		.proc_handler	= perf_event_max_stack_handler,
> > > > +		.extra1		= &zero,
> > > > +	},
> >  
> > > you need to define a max value otherwise perf_callchain_entry__sizeof
> > > will overflow. Sure it's root only facility, but still not nice.
> > > 1M? Anything above 1M stack frames would be insane anyway.
> > > The rest looks good. Thanks!
> > 
> > Something else? ;-)
> 
> all looks good to me. Thanks a bunch!

Thanks for checking!
 
> >     Because we only allocate the callchain percpu data structures when there
> >     is a user, which allows for changing the max easily, its just a matter
> >     of having no callchain users at that point.
> >     
> >     Reported-and-Tested-by: Brendan Gregg <brendan.d.gregg@gmail.com>
> >     Acked-by: Alexei Starovoitov <ast@kernel.org>
> 
> yep :)
> hopefully Brendan can give it another spin.

Agreed, and I'm calling it a day anyway, Brendan, please consider
retesting, thanks,

- Arnaldo