linux-kernel - Re: [PATCH v3 01/11] perf tools: Add API to pause/resume a evlist

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Date:	Mon, 23 May 2016 18:24:55 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Wang Nan <wangnan0@...wei.com>
Cc:	pi3orama@....com, linux-kernel@...r.kernel.org,
	He Kuang <hekuang@...wei.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Zefan Li <lizefan@...wei.com>
Subject: Re: [PATCH v3 01/11] perf tools: Add API to pause/resume a evlist

Em Mon, May 23, 2016 at 07:13:38AM +0000, Wang Nan escreveu:
> +++ b/tools/perf/util/evlist.c
> @@ -679,6 +679,38 @@ static struct perf_evsel *perf_evlist__event2evsel(struct perf_evlist *evlist,
>  	return NULL;
>  }
>  
> +static int perf_evlist__set_paused(struct perf_evlist *evlist, bool pause)
> +{
> +	int i;
> +
> +	for (i = 0; i < evlist->nr_mmaps; i++) {
> +		int fd = evlist->mmap[i].fd;
> +		int err;
> +
> +		if (fd < 0)
> +			continue;
> +		err = ioctl(fd, PERF_EVENT_IOC_PAUSE_OUTPUT,
> +			    pause ? 1 : 0);
> +		if (err) {
> +			err = (errno == 0 ? -EINVAL : -errno);
> +			pr_err("Unable to pause output on %d: %s\n",
> +			       fd, strerror(-err));

I changed this to:
		if (err)
			return err;

Like all other ioctl wrappers in evlist.c, i.e. usage model is the same
as with 'ioctl()': -1 indicates that it failed, if code using this
function wants to know more about the reason for the error, check errno.

Ah, we can't use 'pause' as a parameter name, that breaks the build on
Ubuntu 12.04 and other old glibc headers, I fixed that as well.

- Arnaldo

> +			return err;
> +		}
> +	}
> +	return 0;