[PATCH v6 04/10] libperf: Add evsel mmap support

[Rob Herring]

On Fri, Mar 12, 2021 at 6:59 AM Jiri Olsa <jolsa at redhat.com> wrote:
>
> On Wed, Mar 10, 2021 at 05:08:31PM -0700, Rob Herring wrote:
>
> SNIP
>
> > +
> >  static int
> >  sys_perf_event_open(struct perf_event_attr *attr,
> >                   pid_t pid, int cpu, int group_fd,
> > @@ -137,6 +147,8 @@ void perf_evsel__free_fd(struct perf_evsel *evsel)
> >  {
> >       xyarray__delete(evsel->fd);
> >       evsel->fd = NULL;
> > +     xyarray__delete(evsel->mmap);
> > +     evsel->mmap = NULL;
> >  }
> >
> >  void perf_evsel__close(struct perf_evsel *evsel)
> > @@ -156,6 +168,45 @@ void perf_evsel__close_cpu(struct perf_evsel *evsel, int cpu)
> >       perf_evsel__close_fd_cpu(evsel, cpu);
> >  }
> >
> > +int perf_evsel__mmap(struct perf_evsel *evsel, int pages)
> > +{
> > +     int ret, cpu, thread;
> > +     struct perf_mmap_param mp = {
> > +             .prot = PROT_READ | PROT_WRITE,
> > +             .mask = (pages * page_size) - 1,
> > +     };
>
> I don't mind using evsel->fd for dimensions below,
> but we need to check in here that it's defined,
> that perf_evsel__open was called

Right, so I'll add this here:

if (evsel->fd == NULL)
    return -EINVAL;

Note that struct evsel has dimensions in it, but they are only set in
the evlist code. I couldn't tell if that was by design or mistake.

BTW, I just noticed perf_evsel__open is leaking memory on most of its
error paths.

>
> jirka
>
> > +
> > +     if (evsel->mmap == NULL &&
> > +         perf_evsel__alloc_mmap(evsel, xyarray__max_x(evsel->fd), xyarray__max_y(evsel->fd)) < 0)
> > +             return -ENOMEM;
> > +
> > +     for (cpu = 0; cpu < xyarray__max_x(evsel->fd); cpu++) {
> > +             for (thread = 0; thread < xyarray__max_y(evsel->fd); thread++) {
> > +                     int fd = FD(evsel, cpu, thread);
> > +                     struct perf_mmap *map = MMAP(evsel, cpu, thread);
> > +
> > +                     if (fd < 0)
> > +                             continue;
> > +
> > +                     perf_mmap__init(map, NULL, false, NULL);
> > +
> > +                     ret = perf_mmap__mmap(map, &mp, fd, cpu);
> > +                     if (ret)
> > +                             return -1;
> > +             }
> > +     }
> > +
> > +     return 0;
> > +}
> > +
>
> SNIP
>