linux-kernel - Re: [PATCH] perf: Fix inheritance of aux

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Message-ID: <20191007144954.GA88143@gmail.com>
Date:   Mon, 7 Oct 2019 16:49:54 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:     Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf: Fix inheritance of aux_output groups


* Alexander Shishkin <alexander.shishkin@...ux.intel.com> wrote:

> Commit
> 
>   b43762ef010 ("perf: Allow normal events to output AUX data")

Missing 'a', the proper SHA1 is:

    ab43762ef010 ("perf: Allow normal events to output AUX data")

:-)

> forgets to configure aux_output relation in the inherited groups, which
> results in child PEBS events forever failing to schedule.
> 
> Fix this by setting up the AUX output link in the inheritance path.
> 
> Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> ---
>  kernel/events/core.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index f5bb2557d5f6..761995f21b30 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -12024,6 +12024,10 @@ static int inherit_group(struct perf_event *parent_event,
>  					    child, leader, child_ctx);
>  		if (IS_ERR(child_ctr))
>  			return PTR_ERR(child_ctr);
> +
> +		if (sub->aux_event == parent_event &&
> +		    !perf_get_aux_event(child_ctr, leader))
> +			return -EINVAL;

Could this explain weird 'perf top' failures I'm seeing on my desktop, 
which I was just about to debug and report?

Thanks,

	Ingo