1 files changed, 48 insertions, 3 deletions

diff --git a/tools/perf/util/callchain.c b/tools/perf/util/callchain.c
index d7b7eef740b9..428e5350d7a2 100644
--- a/tools/perf/util/callchain.c
+++ b/tools/perf/util/callchain.c
@@ -275,9 +275,13 @@ int parse_callchain_record(const char *arg, struct callchain_param *param)
 			if (tok) {
 				unsigned long size;
 
-				size = strtoul(tok, &name, 0);
-				if (size < (unsigned) sysctl__max_stack())
-					param->max_stack = size;
+				if (!strncmp(tok, "defer", sizeof("defer"))) {
+					param->defer = true;
+				} else {
+					size = strtoul(tok, &name, 0);
+					if (size < (unsigned) sysctl__max_stack())
+						param->max_stack = size;
+				}
 			}
 			break;
 
@@ -314,6 +318,12 @@ int parse_callchain_record(const char *arg, struct callchain_param *param)
 	} while (0);
 
 	free(buf);
+
+	if (param->defer && param->record_mode != CALLCHAIN_FP) {
+		pr_err("callchain: deferred callchain only works with FP\n");
+		return -EINVAL;
+	}
+
 	return ret;
 }
 
@@ -1828,3 +1838,38 @@ int sample__for_each_callchain_node(struct thread *thread, struct evsel *evsel,
 	}
 	return 0;
 }
+
+/*
+ * This function merges earlier samples (@sample_orig) waiting for deferred
+ * user callchains with the matching callchain record (@sample_callchain)
+ * which is delivered now.  The @sample_orig->callchain should be released
+ * after use if ->deferred_callchain is set.
+ */
+int sample__merge_deferred_callchain(struct perf_sample *sample_orig,
+				     struct perf_sample *sample_callchain)
+{
+	u64 nr_orig = sample_orig->callchain->nr - 1;
+	u64 nr_deferred = sample_callchain->callchain->nr;
+	struct ip_callchain *callchain;
+
+	if (sample_orig->callchain->nr < 2) {
+		sample_orig->deferred_callchain = false;
+		return -EINVAL;
+	}
+
+	callchain = calloc(1 + nr_orig + nr_deferred, sizeof(u64));
+	if (callchain == NULL) {
+		sample_orig->deferred_callchain = false;
+		return -ENOMEM;
+	}
+
+	callchain->nr = nr_orig + nr_deferred;
+	/* copy original including PERF_CONTEXT_USER_DEFERRED (but the cookie) */
+	memcpy(callchain->ips, sample_orig->callchain->ips, nr_orig * sizeof(u64));
+	/* copy deferred user callchains */
+	memcpy(&callchain->ips[nr_orig], sample_callchain->callchain->ips,
+	       nr_deferred * sizeof(u64));
+
+	sample_orig->callchain = callchain;
+	return 0;
+}