linux-kernel - [PATCH 3/5] perf namespaces: Introduce nsinfo__set_in

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Message-ID: <20241206204828.507527-4-acme@kernel.org>
Date: Fri,  6 Dec 2024 17:48:26 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Stephane Eranian <eranian@...gle.com>,
	Yonatan Goldschmidt <yonatan.goldschmidt@...nulate.io>
Cc: Francesco Nigro <fnigro@...hat.com>,
	Ilan Green <igreen@...hat.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	James Clark <james.clark@...aro.org>,
	Jiri Olsa <jolsa@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Kan Liang <kan.liang@...ux.intel.com>,
	Clark Williams <williams@...hat.com>,
	linux-kernel@...r.kernel.org,
	linux-perf-users@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 3/5] perf namespaces: Introduce nsinfo__set_in_pidns()

From: Arnaldo Carvalho de Melo <acme@...hat.com>

When we're processing a perf.data file we will, for every thread in that
file do a machine__findnew_thread(machine, pid, tid) that when that pid
is seen for the first time will create a 'struct thread' representing
it.

That in turn will call nsinfo__new() -> nsinfo__init() and there it will
assume we're running live, which is wrong and will need to be addressed
in a followup patch.

The nsinfo__new() assumes that if we can't access that thread it has
already finished and will ignore the -1 return from nsinfo__init(), just
taking notes to avoid trying to enter in that namespace, since it isn't
there anymore, a race.

When doing this from 'perf inject', tho, we can fill in parts of that
nsinfo from what we get from the PERF_RECORD_MMAP2 (pid, tid) and in the
jitdump file name, that has the form of jit-<PID>.dump.

So if the pid in the jitdump file name is not the one in the
PERF_RECORD_MMAP2, we can assume that its the pid of the process
_inside_ the namespace, and that perf was runing outside that namespace.

This will be done in the following patch.

Reported-by: Francesco Nigro <fnigro@...hat.com>
Reported-by: Ilan Green <igreen@...hat.com>
Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: Ian Rogers <irogers@...gle.com>
Cc: James Clark <james.clark@...aro.org>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Kan Liang <kan.liang@...ux.intel.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Stephane Eranian <eranian@...gle.com>
Cc: Yonatan Goldschmidt <yonatan.goldschmidt@...nulate.io>
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/namespaces.c | 5 +++++
 tools/perf/util/namespaces.h | 1 +
 2 files changed, 6 insertions(+)

diff --git a/tools/perf/util/namespaces.c b/tools/perf/util/namespaces.c
index cb185c5659d6b323..36047184d76e2f80 100644
--- a/tools/perf/util/namespaces.c
+++ b/tools/perf/util/namespaces.c
@@ -271,6 +271,11 @@ pid_t nsinfo__in_pidns(const struct nsinfo  *nsi)
 	return RC_CHK_ACCESS(nsi)->in_pidns;
 }
 
+void nsinfo__set_in_pidns(struct nsinfo *nsi)
+{
+	RC_CHK_ACCESS(nsi)->in_pidns = true;
+}
+
 void nsinfo__mountns_enter(struct nsinfo *nsi,
 				  struct nscookie *nc)
 {
diff --git a/tools/perf/util/namespaces.h b/tools/perf/util/namespaces.h
index 8c0731c6cbb7ee01..e014becb9cd8eb3a 100644
--- a/tools/perf/util/namespaces.h
+++ b/tools/perf/util/namespaces.h
@@ -59,6 +59,7 @@ pid_t nsinfo__tgid(const struct nsinfo  *nsi);
 pid_t nsinfo__nstgid(const struct nsinfo  *nsi);
 pid_t nsinfo__pid(const struct nsinfo  *nsi);
 pid_t nsinfo__in_pidns(const struct nsinfo  *nsi);
+void nsinfo__set_in_pidns(struct nsinfo *nsi);
 
 void nsinfo__mountns_enter(struct nsinfo *nsi, struct nscookie *nc);
 void nsinfo__mountns_exit(struct nscookie *nc);
-- 
2.47.0