[PATCH v1 2/2] perf srcline: Add a timeout to reading from addr2line

[Ian Rogers]

addr2line may fail to send expected values causing perf to wait
indefinitely. Add a 1 second timeout (twice the timeout for reading
from /proc/pid/maps) so that such reads don't cause perf to appear to
lock up.

There are already checks that the file for addr2line contains a debug
section but this isn't always sufficient. The problem was observed
when a valid elf file would set the configuration for binutils
addr2line, then a later read of vmlinux with ELF debug sections would
cause a failing write/read which would block indefinitely.

As a service to future readers, if the io hits eof or an error,
cleanup the addr2line process.

Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
 tools/perf/util/config.c  |  7 +++++--
 tools/perf/util/srcline.c | 11 ++++++++---
 tools/perf/util/srcline.h |  1 +
 3 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/config.c b/tools/perf/util/config.c
index f340dc73db6d..46f144c46827 100644
--- a/tools/perf/util/config.c
+++ b/tools/perf/util/config.c
@@ -19,6 +19,7 @@
 #include "util/llvm-utils.h"   /* perf_llvm_config */
 #include "util/stat.h"  /* perf_stat__set_big_num */
 #include "util/evsel.h"  /* evsel__hw_names, evsel__use_bpf_counters */
+#include "util/srcline.h"  /* addr2line_timeout_ms */
 #include "build-id.h"
 #include "debug.h"
 #include "config.h"
@@ -434,12 +435,14 @@ static int perf_buildid_config(const char *var, const char *value)
 	return 0;
 }
 
-static int perf_default_core_config(const char *var __maybe_unused,
-				    const char *value __maybe_unused)
+static int perf_default_core_config(const char *var, const char *value)
 {
 	if (!strcmp(var, "core.proc-map-timeout"))
 		proc_map_timeout = strtoul(value, NULL, 10);
 
+	if (!strcmp(var, "core.addr2line-timeout"))
+		addr2line_timeout_ms = strtoul(value, NULL, 10);
+
 	/* Add other config variables here. */
 	return 0;
 }
diff --git a/tools/perf/util/srcline.c b/tools/perf/util/srcline.c
index cfca03abd6f8..e06a345c5d19 100644
--- a/tools/perf/util/srcline.c
+++ b/tools/perf/util/srcline.c
@@ -21,6 +21,8 @@
 #include "symbol.h"
 #include "subcmd/run-command.h"
 
+/* If addr2line doesn't return data for 1 second then timeout. */
+int addr2line_timeout_ms = 1 * 1000;
 bool srcline_full_filename;
 
 static const char *dso__name(struct dso *dso)
@@ -512,7 +514,6 @@ static int read_addr2line_record(struct io *io,
 		zfree(&line);
 		return 0;
 	}
-
 	if (function != NULL)
 		*function = strdup(strim(line));
 
@@ -574,7 +575,7 @@ static int addr2line(const char *dso_name, u64 addr,
 	int len;
 	char buf[128];
 	ssize_t written;
-	struct io io;
+	struct io io = { .eof = false };
 	enum a2l_style a2l_style;
 
 	if (!a2l) {
@@ -616,7 +617,7 @@ static int addr2line(const char *dso_name, u64 addr,
 		goto out;
 	}
 	io__init(&io, a2l->out, buf, sizeof(buf));
-
+	io.timeout_ms = addr2line_timeout_ms;
 	switch (read_addr2line_record(&io, a2l_style,
 				      &record_function, &record_filename, &record_line_nr)) {
 	case -1:
@@ -686,6 +687,10 @@ static int addr2line(const char *dso_name, u64 addr,
 out:
 	free(record_function);
 	free(record_filename);
+	if (io.eof) {
+		dso->a2l = NULL;
+		addr2line_subprocess_cleanup(a2l);
+	}
 	return ret;
 }
 
diff --git a/tools/perf/util/srcline.h b/tools/perf/util/srcline.h
index b11a0aaaa676..35a5ff3e78f5 100644
--- a/tools/perf/util/srcline.h
+++ b/tools/perf/util/srcline.h
@@ -9,6 +9,7 @@
 struct dso;
 struct symbol;
 
+extern int addr2line_timeout_ms;
 extern bool srcline_full_filename;
 char *get_srcline(struct dso *dso, u64 addr, struct symbol *sym,
 		  bool show_sym, bool show_addr, u64 ip);
-- 
2.41.0.rc0.172.g3f132b7071-goog