[tip: perf/core] libperf: Centralize map refcnt setting

tip-bot2 for Jiri Olsa
2019-10-15T05:31:51Z

The following commit has been merged into the perf/core branch of tip:

Commit-ID: 285aaeac8c5d537b56b70169e21ac29ae5caa8e1
Gitweb: https://git.kernel.org/tip/285aaeac8c5d537b56b70169e21ac29ae5caa8e1
Author: Jiri Olsa <jolsa@kernel.org>
AuthorDate: Mon, 07 Oct 2019 14:53:30 +02:00
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitterDate: Thu, 10 Oct 2019 12:52:41 -03:00

libperf: Centralize map refcnt setting

Currently when a new map is mmapped we set its refcnt to 2 in the
perf_evlist_mmap_ops::mmap callback.

Every mmap gets its refcnt set to 2 when it's first mmaped:

- 1 for the current user, which will be taken out by a call to
perf_evlist__munmap_filtered(), where we find out there's
no more data comming from kernel to this mmap.

- 1 for the drain code where in perf_mmap__consume() the mmap
is released if it is empty.

Move this common setup into libperf's generic code before the mmap
callback is called.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20191007125344.14268-23-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/lib/evlist.c | 30 +++++++++++++++---------------
tools/perf/util/mmap.c | 15 ---------------
2 files changed, 15 insertions(+), 30 deletions(-)

diff --git a/tools/perf/lib/evlist.c b/tools/perf/lib/evlist.c
index b697226..f9a802d 100644
--- a/tools/perf/lib/evlist.c
+++ b/tools/perf/lib/evlist.c
@@ -362,21 +362,6 @@ static int
perf_evlist__mmap_cb_mmap(struct perf_mmap *map, struct perf_mmap_param *mp,
int output, int cpu)
{
- /*
- * The last one will be done at perf_mmap__consume(), so that we
- * make sure we don't prevent tools from consuming every last event in
- * the ring buffer.
- *
- * I.e. we can get the POLLHUP meaning that the fd doesn't exist
- * anymore, but the last events for it are still in the ring buffer,
- * waiting to be consumed.
- *
- * Tools can chose to ignore this at their own discretion, but the
- * evlist layer can't just drop it when filtering events in
- * perf_evlist__filter_pollfd().
- */
- refcount_set(&map->refcnt, 2);
-
return perf_mmap__mmap(map, mp, output, cpu);
}

@@ -418,6 +403,21 @@ mmap_per_evsel(struct perf_evlist *evlist, struct perf_evlist_mmap_ops *ops,
if (*output == -1) {
*output = fd;

+ /*
+ * The last one will be done at perf_mmap__consume(), so that we
+ * make sure we don't prevent tools from consuming every last event in
+ * the ring buffer.
+ *
+ * I.e. we can get the POLLHUP meaning that the fd doesn't exist
+ * anymore, but the last events for it are still in the ring buffer,
+ * waiting to be consumed.
+ *
+ * Tools can chose to ignore this at their own discretion, but the
+ * evlist layer can't just drop it when filtering events in
+ * perf_evlist__filter_pollfd().
+ */
+ refcount_set(&map->refcnt, 2);
+
if (ops->mmap(map, mp, *output, evlist_cpu) < 0)
return -1;
} else {
diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
index 2a8bf0a..063d1b9 100644
--- a/tools/perf/util/mmap.c
+++ b/tools/perf/util/mmap.c
@@ -243,21 +243,6 @@ static void perf_mmap__setup_affinity_mask(struct mmap *map, struct mmap_params

int mmap__mmap(struct mmap *map, struct mmap_params *mp, int fd, int cpu)
{
- /*
- * The last one will be done at perf_mmap__consume(), so that we
- * make sure we don't prevent tools from consuming every last event in
- * the ring buffer.
- *
- * I.e. we can get the POLLHUP meaning that the fd doesn't exist
- * anymore, but the last events for it are still in the ring buffer,
- * waiting to be consumed.
- *
- * Tools can chose to ignore this at their own discretion, but the
- * evlist layer can't just drop it when filtering events in
- * perf_evlist__filter_pollfd().
- */
- refcount_set(&map->core.refcnt, 2);
-
if (perf_mmap__mmap(&map->core, &mp->core, fd, cpu)) {
pr_debug2("failed to mmap perf event ring buffer, error %d\n",
errno);