linux-kernel - Re: [PATCH v3 2/2]: perf record: enable asynchronous trace writing

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Date:   Tue, 28 Aug 2018 10:53:43 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/2]: perf record: enable asynchronous trace writing

On Mon, Aug 27, 2018 at 09:16:55PM +0300, Alexey Budankov wrote:

SNIP

>  	if ((md->start & md->mask) + size != (md->end & md->mask)) {
>  		buf = &data[md->start & md->mask];
> -		size = md->mask + 1 - (md->start & md->mask);
> -		md->start += size;
> -
> -		if (push(to, buf, size) < 0) {
> -			rc = -1;
> -			goto out;
> -		}
> +		size0 = md->mask + 1 - (md->start & md->mask);
> +		md->start += size0;
> +		memcpy(md->data, buf, size0);
>  	}
>  
>  	buf = &data[md->start & md->mask];
>  	size = md->end - md->start;
>  	md->start += size;
> +	memcpy(md->data + size0, buf, size);
>  
> -	if (push(to, buf, size) < 0) {
> -		rc = -1;
> +	rc = push(to, md, size0 + size, *off) < 0 ? -1 : 1;
> +	if (rc == -1)
>  		goto out;
> -	}
> +
> +	perf_mmap__get(md);
> +	*off += size0 + size;

this get is for the perf_mmap pointer storage in the mmap_aio array right?

I see it's released in record__mmap_read_sync, which might also return
without releasing it.. this needs to be fixed and explained in here,
why we take the reference in the first place

thanks,
jirka