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SubjectRe: [PATCH 6/7] libperF: Add group support to perf_evsel__open
Em Tue, Jul 06, 2021 at 05:17:03PM +0200, Jiri Olsa escreveu:
> Adding support to set group_fd in perf_evsel__open
> call and make it to follow the group setup.
>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
> tools/lib/perf/evsel.c | 26 ++++++++++++++++++++++++--
> 1 file changed, 24 insertions(+), 2 deletions(-)
>
> diff --git a/tools/lib/perf/evsel.c b/tools/lib/perf/evsel.c
> index 3e6638d27c45..9ebf7122d476 100644
> --- a/tools/lib/perf/evsel.c
> +++ b/tools/lib/perf/evsel.c
> @@ -17,6 +17,7 @@
> #include <linux/string.h>
> #include <sys/ioctl.h>
> #include <sys/mman.h>
> +#include <asm/bug.h>
>
> void perf_evsel__init(struct perf_evsel *evsel, struct perf_event_attr *attr,
> int idx)
> @@ -76,6 +77,25 @@ sys_perf_event_open(struct perf_event_attr *attr,
> return syscall(__NR_perf_event_open, attr, pid, cpu, group_fd, flags);
> }
>
> +static int get_group_fd(struct perf_evsel *evsel, int cpu, int thread)
> +{
> + struct perf_evsel *leader = evsel->leader;
> + int fd;
> +
> + if (evsel == leader)
> + return -1;
> +
> + /*
> + * Leader must be already processed/open,
> + * if not it's a bug.
> + */
> + BUG_ON(!leader->fd);

Humm, having panics in library code looks ugly, why can't we just return
some errno and let the whatever is using the library to fail gracefully?

I applied the patches so far, will make them available at tmp.perf/core
now.

- Arnaldo

> + fd = FD(leader, cpu, thread);
> + BUG_ON(fd == -1);
> + return fd;
> +}
> +
> int perf_evsel__open(struct perf_evsel *evsel, struct perf_cpu_map *cpus,
> struct perf_thread_map *threads)
> {
> @@ -111,11 +131,13 @@ 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;
> + int fd, group_fd;
> +
> + group_fd = get_group_fd(evsel, cpu, thread);
>
> fd = sys_perf_event_open(&evsel->attr,
> threads->map[thread].pid,
> - cpus->map[cpu], -1, 0);
> + cpus->map[cpu], group_fd, 0);
>
> if (fd < 0)
> return -errno;
> --
> 2.31.1
>

--

- Arnaldo

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