perf symbols: Check if we read regular file in dso__load()

The current code in dso__load() calls is_regular_file(), but it checks
its return value only after calling symsrc__init().

That can make symsrc__init() block in elf_* functions on reading
the file if the file happens to be device and not regular one.

Call symsrc__init() only for regular files. Also remove the
symsrc__destroy() cleanup, which is not needed now, because we call
symsrc__init() only for regular files.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180215122635.24029-3-jolsa@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/symbol.c

@@ -1582,7 +1582,7 @@ int dso__load(struct dso *dso, struct map *map)
 		bool next_slot = false;
 		bool is_reg;
 		bool nsexit;
-		int sirc;
+		int sirc = -1;
 
 		enum dso_binary_type symtab_type = binary_type_symtab[i];
 
@@ -1600,16 +1600,14 @@ int dso__load(struct dso *dso, struct map *map)
 			nsinfo__mountns_exit(&nsc);
 
 		is_reg = is_regular_file(name);
+		if (is_reg)
 			sirc = symsrc__init(ss, dso, name, symtab_type);
 
 		if (nsexit)
 			nsinfo__mountns_enter(dso->nsinfo, &nsc);
 
-		if (!is_reg || sirc < 0) {
-			if (sirc >= 0)
-				symsrc__destroy(ss);
+		if (!is_reg || sirc < 0)
 			continue;
-		}
 
 		if (!syms_ss && symsrc__has_symtab(ss)) {
 			syms_ss = ss;