perf tools: Compare dso's also when comparing symbols

Linus reported that sometimes 'perf report -s symbol' exits without any
message on TUI.  David and Jiri found that it's because it failed to add
a hist entry due to an invalid symbol length.

It turns out that sorting by symbol (address) was broken since it only
compares symbol addresses.  The symbol address is a relative address
within a dso thus just checking its address can result in merging
unrelated symbols together.  Fix it by checking dso before comparing
symbol address.

Reported-by: Linus Torvalds <[email protected]>
Signed-off-by: Namhyung Kim <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

tools/perf/util/sort.c

@@ -182,9 +182,19 @@ static int64_t _sort__sym_cmp(struct symbol *sym_l, struct symbol *sym_r)
 static int64_t
 sort__sym_cmp(struct hist_entry *left, struct hist_entry *right)
 {
+	int64_t ret;
+
 	if (!left->ms.sym && !right->ms.sym)
 		return right->level - left->level;
 
+	/*
+	 * comparing symbol address alone is not enough since it's a
+	 * relative address within a dso.
+	 */
+	ret = sort__dso_cmp(left, right);
+	if (ret != 0)
+		return ret;
+
 	return _sort__sym_cmp(left->ms.sym, right->ms.sym);
 }