Re: [PATCH v2] libperf evsel: Make use of FD robust.
From: Ian Rogers
Date: Fri Sep 17 2021 - 15:20:01 EST
On Thu, Sep 16, 2021 at 1:03 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
>
> On Wed, Sep 15, 2021 at 11:22:39PM -0700, Ian Rogers wrote:
>
> SNIP
>
> > v2. is a rebase.
> >
> > Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
> > ---
> > tools/lib/perf/evsel.c | 64 +++++++++++++++++++++++++++---------------
> > 1 file changed, 41 insertions(+), 23 deletions(-)
> >
> > diff --git a/tools/lib/perf/evsel.c b/tools/lib/perf/evsel.c
> > index d8886720e83d..ede7af4d183c 100644
> > --- a/tools/lib/perf/evsel.c
> > +++ b/tools/lib/perf/evsel.c
> > @@ -43,7 +43,7 @@ void perf_evsel__delete(struct perf_evsel *evsel)
> > free(evsel);
> > }
> >
> > -#define FD(e, x, y) (*(int *) xyarray__entry(e->fd, x, y))
> > +#define FD(e, x, y) (int *) xyarray__entry(e->fd, x, y)
> > #define MMAP(e, x, y) (e->mmap ? ((struct perf_mmap *) xyarray__entry(e->mmap, x, y)) : NULL)
> >
> > int perf_evsel__alloc_fd(struct perf_evsel *evsel, int ncpus, int nthreads)
> > @@ -54,7 +54,10 @@ int perf_evsel__alloc_fd(struct perf_evsel *evsel, int ncpus, int nthreads)
> > int cpu, thread;
> > for (cpu = 0; cpu < ncpus; cpu++) {
> > for (thread = 0; thread < nthreads; thread++) {
> > - FD(evsel, cpu, thread) = -1;
> > + int *fd = FD(evsel, cpu, thread);
> > +
> > + if (fd)
> > + *fd = -1;
>
> so it's the perf_thread open that uses empty cpus and evlist__close
> will have more cpus to work on
>
> I'd expect some symetric fix on close path, but evlist__close is
> generic, so it's probably the best fix ;-)
>
> Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Thanks! Arnaldo is there anything more to do on this? It'd be nice to
fix the crashes seen in:
https://lore.kernel.org/linux-perf-users/20210917184240.2181186-1-irogers@xxxxxxxxxx/T/#t
Thanks!
Ian
> thanks,
> jirka
>
>
> > }
> > }
> > }
> > @@ -80,7 +83,7 @@ sys_perf_event_open(struct perf_event_attr *attr,
> > static int get_group_fd(struct perf_evsel *evsel, int cpu, int thread, int *group_fd)
> > {
> > struct perf_evsel *leader = evsel->leader;
> > - int fd;
> > + int *fd;
> >
> > if (evsel == leader) {
> > *group_fd = -1;
> > @@ -95,10 +98,10 @@ static int get_group_fd(struct perf_evsel *evsel, int cpu, int thread, int *grou
> > return -ENOTCONN;
> >
> > fd = FD(leader, cpu, thread);
> > - if (fd == -1)
> > + if (fd == NULL || *fd == -1)
> > return -EBADF;
> >
> > - *group_fd = fd;
> > + *group_fd = *fd;
> >
> > return 0;
> > }
> > @@ -138,7 +141,11 @@ int perf_evsel__open(struct perf_evsel *evsel, struct perf_cpu_map *cpus,
> >
> > for (cpu = 0; cpu < cpus->nr; cpu++) {
> > for (thread = 0; thread < threads->nr; thread++) {
> > - int fd, group_fd;
> > + int fd, group_fd, *evsel_fd;
> > +
> > + evsel_fd = FD(evsel, cpu, thread);
> > + if (evsel_fd == NULL)
> > + return -EINVAL;
> >
> > err = get_group_fd(evsel, cpu, thread, &group_fd);
> > if (err < 0)
> > @@ -151,7 +158,7 @@ int perf_evsel__open(struct perf_evsel *evsel, struct perf_cpu_map *cpus,
> > if (fd < 0)
> > return -errno;
> >
> > - FD(evsel, cpu, thread) = fd;
> > + *evsel_fd = fd;
> > }
> > }
> >
> > @@ -163,9 +170,12 @@ static void perf_evsel__close_fd_cpu(struct perf_evsel *evsel, int cpu)
> > int thread;
> >
> > for (thread = 0; thread < xyarray__max_y(evsel->fd); ++thread) {
> > - if (FD(evsel, cpu, thread) >= 0)
> > - close(FD(evsel, cpu, thread));
> > - FD(evsel, cpu, thread) = -1;
> > + int *fd = FD(evsel, cpu, thread);
> > +
> > + if (fd && *fd >= 0) {
> > + close(*fd);
> > + *fd = -1;
> > + }
> > }
> > }
> >
> > @@ -209,13 +219,12 @@ void perf_evsel__munmap(struct perf_evsel *evsel)
> >
> > 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);
> > + int *fd = FD(evsel, cpu, thread);
> >
> > - if (fd < 0)
> > + if (fd == NULL || *fd < 0)
> > continue;
> >
> > - perf_mmap__munmap(map);
> > + perf_mmap__munmap(MMAP(evsel, cpu, thread));
> > }
> > }
> >
> > @@ -239,15 +248,16 @@ int perf_evsel__mmap(struct perf_evsel *evsel, int pages)
> >
> > 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);
> > + int *fd = FD(evsel, cpu, thread);
> > + struct perf_mmap *map;
> >
> > - if (fd < 0)
> > + if (fd == NULL || *fd < 0)
> > continue;
> >
> > + map = MMAP(evsel, cpu, thread);
> > perf_mmap__init(map, NULL, false, NULL);
> >
> > - ret = perf_mmap__mmap(map, &mp, fd, cpu);
> > + ret = perf_mmap__mmap(map, &mp, *fd, cpu);
> > if (ret) {
> > perf_evsel__munmap(evsel);
> > return ret;
> > @@ -260,7 +270,9 @@ int perf_evsel__mmap(struct perf_evsel *evsel, int pages)
> >
> > void *perf_evsel__mmap_base(struct perf_evsel *evsel, int cpu, int thread)
> > {
> > - if (FD(evsel, cpu, thread) < 0 || MMAP(evsel, cpu, thread) == NULL)
> > + int *fd = FD(evsel, cpu, thread);
> > +
> > + if (fd == NULL || *fd < 0 || MMAP(evsel, cpu, thread) == NULL)
> > return NULL;
> >
> > return MMAP(evsel, cpu, thread)->base;
> > @@ -295,17 +307,18 @@ int perf_evsel__read(struct perf_evsel *evsel, int cpu, int thread,
> > struct perf_counts_values *count)
> > {
> > size_t size = perf_evsel__read_size(evsel);
> > + int *fd = FD(evsel, cpu, thread);
> >
> > memset(count, 0, sizeof(*count));
> >
> > - if (FD(evsel, cpu, thread) < 0)
> > + if (fd == NULL || *fd < 0)
> > return -EINVAL;
> >
> > if (MMAP(evsel, cpu, thread) &&
> > !perf_mmap__read_self(MMAP(evsel, cpu, thread), count))
> > return 0;
> >
> > - if (readn(FD(evsel, cpu, thread), count->values, size) <= 0)
> > + if (readn(*fd, count->values, size) <= 0)
> > return -errno;
> >
> > return 0;
> > @@ -318,8 +331,13 @@ static int perf_evsel__run_ioctl(struct perf_evsel *evsel,
> > int thread;
> >
> > for (thread = 0; thread < xyarray__max_y(evsel->fd); thread++) {
> > - int fd = FD(evsel, cpu, thread),
> > - err = ioctl(fd, ioc, arg);
> > + int err;
> > + int *fd = FD(evsel, cpu, thread);
> > +
> > + if (fd || *fd < 0)
> > + return -1;
> > +
> > + err = ioctl(*fd, ioc, arg);
> >
> > if (err)
> > return err;
> > --
> > 2.33.0.309.g3052b89438-goog
> >
>