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SubjectRe: [PATCH 6/7] libperF: Add group support to perf_evsel__open
On Wed, Jul 07, 2021 at 02:43:07PM -0300, Arnaldo Carvalho de Melo wrote:
> 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?

true, I took it from perf code, did not realize this,
I'll check what can we do in ehre

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

great, I'll take the patches from there for my next change

thanks,
jirka

>
> - 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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