perf lock contention: Show full callstack with -v option

Currently it shows a caller function for each entry, but users need to see
the full call stacks sometimes.  Use -v/--verbose option to do that.

  # perf lock con -a -b -v sleep 3
  Looking at the vmlinux_path (8 entries long)
  symsrc__init: cannot get elf header.
  Using /proc/kcore for kernel data
  Using /proc/kallsyms for symbols
   contended   total wait     max wait     avg wait         type   caller

           1     10.74 us     10.74 us     10.74 us     spinlock   __bpf_trace_contention_begin+0xb
                          0xffffffffc03b5c47  bpf_prog_bf07ae9e2cbd02c5_contention_begin+0x117
                          0xffffffffc03b5c47  bpf_prog_bf07ae9e2cbd02c5_contention_begin+0x117
                          0xffffffffbb8b8e75  bpf_trace_run2+0x35
                          0xffffffffbb7eab9b  __bpf_trace_contention_begin+0xb
                          0xffffffffbb7ebe75  queued_spin_lock_slowpath+0x1f5
                          0xffffffffbc1c26ff  _raw_spin_lock+0x1f
                          0xffffffffbb841015  tick_do_update_jiffies64+0x25
                          0xffffffffbb8409ee  tick_irq_enter+0x9e
           1      7.70 us      7.70 us      7.70 us     spinlock   __bpf_trace_contention_begin+0xb
                          0xffffffffc03b5c47  bpf_prog_bf07ae9e2cbd02c5_contention_begin+0x117
                          0xffffffffc03b5c47  bpf_prog_bf07ae9e2cbd02c5_contention_begin+0x117
                          0xffffffffbb8b8e75  bpf_trace_run2+0x35
                          0xffffffffbb7eab9b  __bpf_trace_contention_begin+0xb
                          0xffffffffbb7ebe75  queued_spin_lock_slowpath+0x1f5
                          0xffffffffbc1c26ff  _raw_spin_lock+0x1f
                          0xffffffffbb7bc27e  raw_spin_rq_lock_nested+0xe
                          0xffffffffbb7cef9c  load_balance+0x66c

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20220912055314.744552-3-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-lock.c

@@ -1014,6 +1014,27 @@ next:
 	return hash;
 }
 
+static u64 *get_callstack(struct perf_sample *sample, int max_stack)
+{
+	u64 *callstack;
+	u64 i;
+	int c;
+
+	callstack = calloc(max_stack, sizeof(*callstack));
+	if (callstack == NULL)
+		return NULL;
+
+	for (i = 0, c = 0; i < sample->callchain->nr && c < max_stack; i++) {
+		u64 ip = sample->callchain->ips[i];
+
+		if (ip >= PERF_CONTEXT_MAX)
+			continue;
+
+		callstack[c++] = ip;
+	}
+	return callstack;
+}
+
 static int report_lock_contention_begin_event(struct evsel *evsel,
 					      struct perf_sample *sample)
 {
@@ -1040,6 +1061,12 @@ static int report_lock_contention_begin_event(struct evsel *evsel,
 		ls = lock_stat_findnew(key, caller, flags);
 		if (!ls)
 			return -ENOMEM;
+
+		if (aggr_mode == LOCK_AGGR_CALLER && verbose) {
+			ls->callstack = get_callstack(sample, CONTENTION_STACK_DEPTH);
+			if (ls->callstack == NULL)
+				return -ENOMEM;
+		}
 	}
 
 	ts = thread_stat_findnew(sample->tid);
@@ -1443,7 +1470,7 @@ static void sort_contention_result(void)
 	sort_result();
 }
 
-static void print_contention_result(void)
+static void print_contention_result(struct lock_contention *con)
 {
 	struct lock_stat *st;
 	struct lock_key *key;
@@ -1482,6 +1509,22 @@ static void print_contention_result(void)
 		}
 
 		pr_info("  %10s   %s\n", get_type_str(st), st->name);
+		if (verbose) {
+			struct map *kmap;
+			struct symbol *sym;
+			char buf[128];
+			u64 ip;
+
+			for (int i = 0; i < CONTENTION_STACK_DEPTH; i++) {
+				if (!st->callstack || !st->callstack[i])
+					break;
+
+				ip = st->callstack[i];
+				sym = machine__find_kernel_symbol(con->machine, ip, &kmap);
+				get_symbol_name_offset(kmap, sym, ip, buf, sizeof(buf));
+				pr_info("\t\t\t%#lx  %s\n", (unsigned long)ip, buf);
+			}
+		}
 	}
 
 	print_bad_events(bad, total);
@@ -1597,6 +1640,8 @@ static int __cmd_contention(int argc, const char **argv)
 		return PTR_ERR(session);
 	}
 
+	con.machine = &session->machines.host;
+
 	/* for lock function check */
 	symbol_conf.sort_by_name = true;
 	symbol__init(&session->header.env);
@@ -1615,8 +1660,6 @@ static int __cmd_contention(int argc, const char **argv)
 		signal(SIGCHLD, sighandler);
 		signal(SIGTERM, sighandler);
 
-		con.machine = &session->machines.host;
-
 		con.evlist = evlist__new();
 		if (con.evlist == NULL) {
 			err = -ENOMEM;
@@ -1688,7 +1731,7 @@ static int __cmd_contention(int argc, const char **argv)
 	setup_pager();
 
 	sort_contention_result();
-	print_contention_result();
+	print_contention_result(&con);
 
 out_delete:
 	evlist__delete(con.evlist);

tools/perf/util/bpf_lock_contention.c

@@ -8,6 +8,7 @@
 #include "util/thread_map.h"
 #include "util/lock-contention.h"
 #include <linux/zalloc.h>
+#include <linux/string.h>
 #include <bpf/bpf.h>
 
 #include "bpf_skel/lock_contention.skel.h"
@@ -171,6 +172,14 @@ int lock_contention_read(struct lock_contention *con)
 			return -1;
 		}
 
+		if (verbose) {
+			st->callstack = memdup(stack_trace, sizeof(stack_trace));
+			if (st->callstack == NULL) {
+				free(st);
+				return -1;
+			}
+		}
+
 		hlist_add_head(&st->hash_entry, con->result);
 		prev_key = key;
 	}

tools/perf/util/lock-contention.h

@@ -11,6 +11,7 @@ struct lock_stat {
 
 	u64			addr;		/* address of lockdep_map, used as ID */
 	char			*name;		/* for strcpy(), we cannot use const */
+	u64			*callstack;
 
 	unsigned int		nr_acquire;
 	unsigned int		nr_acquired;