linux-kernel - Re: [PATCH 7/7] perf tools: Remove prot field in mmap param

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Date:   Mon, 13 Nov 2017 12:52:16 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Wang Nan <wangnan0@...wei.com>
Cc:     linux-kernel@...r.kernel.org, kan.liang@...el.com, acme@...nel.org,
        namhyung@...nel.org
Subject: Re: [PATCH 7/7] perf tools: Remove prot field in mmap param

On Mon, Nov 13, 2017 at 01:38:09AM +0000, Wang Nan wrote:
> After removing the concept of 'overwrite' in code level, now the
> prot is determinated by write_backward. There's no need to pass
> prot from perf_evlist__mmap_ex().
> 
> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> ---
>  tools/perf/util/evlist.c | 17 ++++++-----------
>  tools/perf/util/mmap.c   |  4 ++--
>  tools/perf/util/mmap.h   |  4 ++--
>  3 files changed, 10 insertions(+), 15 deletions(-)
> 
> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> index 4948d3d..0d713e0 100644
> --- a/tools/perf/util/evlist.c
> +++ b/tools/perf/util/evlist.c
> @@ -799,28 +799,23 @@ perf_evlist__should_poll(struct perf_evlist *evlist __maybe_unused,
>  }
>  
>  static int perf_evlist__mmap_per_evsel(struct perf_evlist *evlist, int idx,
> -				       struct mmap_params *_mp, int cpu_idx,
> +				       struct mmap_params *mp, int cpu_idx,
>  				       int thread, int *_output, int *_output_backward)
>  {
>  	struct perf_evsel *evsel;
>  	int revent;
>  	int evlist_cpu = cpu_map__cpu(evlist->cpus, cpu_idx);
> -	struct mmap_params *mp;
>  
>  	evlist__for_each_entry(evlist, evsel) {
>  		struct perf_mmap *maps = evlist->mmap;
> -		struct mmap_params rdonly_mp;
>  		int *output = _output;
>  		int fd;
>  		int cpu;
> +		int prot = PROT_READ;

can't you set the PROT_READ in struct mmap_params *mp as its default value?

		mp->prot = PROT_READ;

>  
> -		mp = _mp;
>  		if (evsel->attr.write_backward) {
>  			output = _output_backward;
>  			maps = evlist->backward_mmap;
> -			rdonly_mp = *_mp;
> -			rdonly_mp.prot &= ~PROT_WRITE;
> -			mp = &rdonly_mp;
>  
>  			if (!maps) {
>  				maps = perf_evlist__alloc_mmap(evlist);
> @@ -830,6 +825,8 @@ static int perf_evlist__mmap_per_evsel(struct perf_evlist *evlist, int idx,
>  				if (evlist->bkw_mmap_state == BKW_MMAP_NOTREADY)
>  					perf_evlist__toggle_bkw_mmap(evlist, BKW_MMAP_RUNNING);
>  			}
> +		} else {
> +			prot |= PROT_WRITE;
>  		}
>  
>  		if (evsel->system_wide && thread)
> @@ -844,7 +841,7 @@ static int perf_evlist__mmap_per_evsel(struct perf_evlist *evlist, int idx,
>  		if (*output == -1) {
>  			*output = fd;
>  
> -			if (perf_mmap__mmap(&maps[idx], mp, *output)  < 0)
> +			if (perf_mmap__mmap(&maps[idx], mp, prot, *output)  < 0)

so there's no need for the extra 'prot' param in here

jirka