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Date: Tue, 26 Jan 2016 17:16:37 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org,
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        Jiri Olsa <jolsa@kernel.org>, Daniel Borkmann <daniel@iogearbox.net>,
        Wang Nan <wangnan0@huawei.com>
Subject: Re: [PATCH v2] perf: Synchronously cleanup child events
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On Mon, Jan 25, 2016 at 08:59:49PM -0800, Alexei Starovoitov wrote:
> I think I understand what you're trying to do and
> the patch looks good to me.

Great, thanks!

> As far as BPF side I did the following...
> does it match the model you outlined above?

Yes, a few comments/questions below.

> 
> Subject: [PATCH ] perf,bpf: convert perf_event_array to use struct file
> 
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Can I take this through the tip/perf tree so that all these changes land
together?

> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 06ae52e99ac2..2a95e0d2370f 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -8896,21 +8896,17 @@ void perf_event_delayed_put(struct task_struct *task)
>  		WARN_ON_ONCE(task->perf_event_ctxp[ctxn]);
>  }
>  
> +struct file *perf_event_get(unsigned int fd)
>  {
> +	struct file *file;
>  
> +	file = fget_raw(fd);

fget_raw() to guarantee the return value isn't NULL? afaict the O_PATH
stuff does not apply to perf events, so you'd put any fd for which the
distinction matters anyway.

> +	if (file->f_op != &perf_fops) {
> +		fput(file);
> +		return ERR_PTR(-EBADF);
> +	}
>  
> +	return file;
>  }