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

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Date:   Mon, 8 Mar 2021 08:54:37 -0800
From:   Andi Kleen <ak@...ux.intel.com>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf auxtrace: Fix auxtrace queue conflict

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>

-Andi