perf tools: Reference count struct dso

This has a different model than the 'thread' and 'map' struct lifetimes:
there is not a definitive "don't use this DSO anymore" event, i.e. we may
get many 'struct map' holding references to the '/usr/lib64/libc-2.20.so'
DSO but then at some point some DSO may have no references but we still
don't want to straight away release its resources, because "soon" we may
get a new 'struct map' that needs it and we want to reuse its symtab or
other resources.

So we need some way to garbage collect it when crossing some memory
usage threshold, which is left for anoter patch, for now it is
sufficient to release it when calling dsos__exit(), i.e. when deleting
the whole list as part of deleting the 'struct machine' containing it,
which will leave only referenced objects being used.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/n/tip-majzgz07cm90t2tejrjy4clf@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 11 insertions, 4 deletions

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 0cf56d6f073a..132e35765101 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -82,7 +82,7 @@ out_delete:
 	return NULL;
 }
 
-static void dsos__exit(struct dsos *dsos)
+static void dsos__purge(struct dsos *dsos)
 {
 	struct dso *pos, *n;
 
@@ -90,12 +90,16 @@ static void dsos__exit(struct dsos *dsos)
 
 	list_for_each_entry_safe(pos, n, &dsos->head, node) {
 		RB_CLEAR_NODE(&pos->rb_node);
-		list_del(&pos->node);
-		dso__delete(pos);
+		list_del_init(&pos->node);
+		dso__put(pos);
 	}
 
 	pthread_rwlock_unlock(&dsos->lock);
+}
 
+static void dsos__exit(struct dsos *dsos)
+{
+	dsos__purge(dsos);
 	pthread_rwlock_destroy(&dsos->lock);
 }
 
@@ -524,6 +528,7 @@ static struct dso *machine__findnew_module_dso(struct machine *machine,
 		dso__set_long_name(dso, strdup(filename), true);
 	}
 
+	dso__get(dso);
 out_unlock:
 	pthread_rwlock_unlock(&machine->dsos.lock);
 	return dso;
@@ -1205,8 +1210,10 @@ static int machine__process_kernel_mmap_event(struct machine *machine,
 			goto out_problem;
 
 		kernel->kernel = kernel_type;
-		if (__machine__create_kernel_maps(machine, kernel) < 0)
+		if (__machine__create_kernel_maps(machine, kernel) < 0) {
+			dso__put(kernel);
 			goto out_problem;
+		}
 
 		if (strstr(kernel->long_name, "vmlinux"))
 			dso__set_short_name(kernel, "[kernel.vmlinux]", false);