linux-kernel - Re: [RFC PATCH 3/8] perf: Init/fini PMU specific data

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Message-ID: <20191202191519.GN84886@tassilo.jf.intel.com>
Date:   Mon, 2 Dec 2019 11:15:19 -0800
From:   Andi Kleen <ak@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     kan.liang@...ux.intel.com, mingo@...hat.com, acme@...nel.org,
        tglx@...utronix.de, bp@...en8.de, linux-kernel@...r.kernel.org,
        eranian@...gle.com, alexey.budankov@...ux.intel.com,
        vitaly.slobodskoy@...el.com
Subject: Re: [RFC PATCH 3/8] perf: Init/fini PMU specific data

On Mon, Dec 02, 2019 at 05:21:52PM +0100, Peter Zijlstra wrote:
> On Mon, Dec 02, 2019 at 06:59:57AM -0800, Andi Kleen wrote:
> > > 
> > > This is atricous crap. Also it is completely broken for -RT.
> > 
> > Well can you please suggest how you would implement it instead?
> 
> I don't think that is on me; at best I get to explain why it is

Normally code review is expected to be constructive.

> completely unacceptible to have O(nr_tasks) and allocations under a
> raw_spinlock_t, but I was thinking you'd already know that.

Ok if that's the only problem then a lock breaker + retry 
if rescheduling is needed + some limit against live lock 
should be sufficient.

-Andi