linux-kernel - Re: [PATCH] perf auxtrace: Fix auxtrace queue conflict

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Message-ID: <YEdrngHYJh3L6zXH@kernel.org>
Date:   Tue, 9 Mar 2021 09:35:42 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     Adrian Hunter <adrian.hunter@...el.com>,
        Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf auxtrace: Fix auxtrace queue conflict

Em Mon, Mar 08, 2021 at 08:54:37AM -0800, Andi Kleen escreveu:
> On Mon, Mar 08, 2021 at 05:11:43PM +0200, Adrian Hunter wrote:
> > The only requirement of an auxtrace queue is that the buffers are in
> > time order.  That is achieved by making separate queues for separate
> > perf buffer or AUX area buffer mmaps.
> > 
> > That generally means a separate queue per cpu for per-cpu contexts,
> > and a separate queue per thread for per-task contexts.
> > 
> > When buffers are added to a queue, perf checks that the buffer cpu
> > and thread id (tid) match the queue cpu and thread id.
> > 
> > However, generally, that need not be true, and perf will queue
> > buffers correctly anyway, so the check is not needed.
> > 
> > In addition, the check gets erroneously hit when using sample mode
> > to trace multiple threads.
> > 
> > Consequently, fix that case by removing the check.
> 
> Thanks!
> 
> Reviewed-by: Andi Kleen <ak@...ux.intel.com>

Thanks, applied.

- Arnaldo