[gdb/testsuite] Fix gdb.reverse/time-reverse.exp timeout

After building gdb with "-O0 -g -fsanitize=thread" on aarch64-linux, with
test-case gdb.reverse/time-reverse.exp I run into:
...
(gdb) continue^M
Continuing.^M
FAIL: $exp: mode=c: continue to breakpoint: marker2 (timeout)
...

The problem is that instruction stepping gets stuck in a loop with this call
stack: time -> __GI___clock_gettime -> __kernel_clock_gettime ->
__cvdso_clock_gettime.

This is not specific to fsanitize=thread, it just makes gdb slow, which makes
instruction stepping slow, which results in the application getting stuck.

I ran into this as well with a regular gdb build on a 32-bit i686 laptop with
1GB of memory, an inherently slow setup.  In that instance, I was able to
observe that the loop we're stuck in is the outer loop in do_coarse in linux
kernel source lib/vdso/gettimeofday.c.

Fix this by setting "record full insn-number-max" to 2000, and handling
running into the limit.

Initially I tried the approach of using "stepi 2000" instead of continue, but
that made the issue more likely to show up (for instance, I observed it after
building gdb with -O0 on aarch64-linux).

Tested on aarch64-linux.

Approved-By: Guinevere Larsen <guinevere@redhat.com>
PR testsuite/32678
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=32678

diff --git a/gdb/testsuite/gdb.reverse/time-reverse.exp b/gdb/testsuite/gdb.reverse/time-reverse.exp
index aa074e91530507e61ae8d3f27b45c940b49a2d76..58dcdde3502d7479bc907b746fc5bffad4ee3c5b 100644 (file)
--- a/gdb/testsuite/gdb.reverse/time-reverse.exp
+++ b/gdb/testsuite/gdb.reverse/time-reverse.exp
@@ -45,6 +45,8 @@ proc test {mode} {
 
     # Activate process record/replay
     gdb_test_no_output "record" "turn on process record"
+    gdb_test_no_output "set record full stop-at-limit on"
+    gdb_test_no_output "set record full insn-number-max 2000"
 
     set re_srcfile [string_to_regexp $::srcfile]
 
@@ -52,7 +54,29 @@ proc test {mode} {
        "Breakpoint $::decimal at $::hex: file .*$re_srcfile, line $::decimal.*" \
        "set breakpoint at marker2"
 
-    gdb_continue_to_breakpoint "marker2" ".*$re_srcfile:.*"
+    set re_question \
+       [string_list_to_regexp \
+            "Do you want to auto delete previous execution log entries when" \
+            " record/replay buffer becomes full" \
+            { (record full stop-at-limit)?([y] or n)}]
+    set re_program_stopped \
+       [multi_line \
+            [string_to_regexp "Process record: stopped by user."] \
+            "" \
+            [string_to_regexp "Program stopped."]]
+    set re_marker2 [string_to_regexp "marker2 ()"]
+    gdb_test_multiple "continue" "continue to breakpoint: marker2" {
+       -re "$re_question " {
+           send_gdb "n\n"
+           exp_continue
+       }
+       -re -wrap "Breakpoint $::decimal, $re_marker2 .*" {
+           pass $gdb_test_name
+       }
+       -re -wrap "\r\n$re_program_stopped\r\n.*" {
+           unsupported $gdb_test_name
+       }
+    }
 
     # Show how many instructions we've recorded.
     gdb_test "info record" "Active record target: .*"