[pushed] Add test for PR18214 and PR18216 - multiple step-overs with queued signals
Commit Message
Both PRs are triggered by the same use case.
PR18214 is about software single-step targets. On those, the 'resume'
code that detects that we're stepping over a breakpoint and delivering
a signal at the same time:
/* Currently, our software single-step implementation leads to different
results than hardware single-stepping in one situation: when stepping
into delivering a signal which has an associated signal handler,
hardware single-step will stop at the first instruction of the handler,
while software single-step will simply skip execution of the handler.
...
Fortunately, we can at least fix this particular issue. We detect
here the case where we are about to deliver a signal while software
single-stepping with breakpoints removed. In this situation, we
revert the decisions to remove all breakpoints and insert single-
step breakpoints, and instead we install a step-resume breakpoint
at the current address, deliver the signal without stepping, and
once we arrive back at the step-resume breakpoint, actually step
over the breakpoint we originally wanted to step over. */
doesn't handle the case of _another_ thread also needing to step over
a breakpoint. Because the other thread is just resumed at the PC
where it had stopped and a breakpoint is still inserted there, the
thread immediately re-traps the same breakpoint. This test exercises
that. On software single-step targets, it fails like this:
KFAIL: gdb.threads/multiple-step-overs.exp: displaced=off: signal thr3: continue to sigusr1_handler
KFAIL: gdb.threads/multiple-step-overs.exp: displaced=off: signal thr2: continue to sigusr1_handler
gdb.log (simplified):
(gdb) continue
Continuing.
Breakpoint 4, child_function_2 (arg=0x0) at src/gdb/testsuite/gdb.threads/multiple-step-overs.c:66
66 callme (); /* set breakpoint thread 2 here */
(gdb) thread 3
(gdb) queue-signal SIGUSR1
(gdb) thread 1
[Switching to thread 1 (Thread 0x7ffff7fc1740 (LWP 24824))]
#0 main () at src/gdb/testsuite/gdb.threads/multiple-step-overs.c:106
106 wait_threads (); /* set wait-threads breakpoint here */
(gdb) break sigusr1_handler
Breakpoint 5 at 0x400837: file src/gdb/testsuite/gdb.threads/multiple-step-overs.c, line 31.
(gdb) continue
Continuing.
[Switching to Thread 0x7ffff7fc0700 (LWP 24828)]
Breakpoint 4, child_function_2 (arg=0x0) at src/gdb/testsuite/gdb.threads/multiple-step-overs.c:66
66 callme (); /* set breakpoint thread 2 here */
(gdb) KFAIL: gdb.threads/multiple-step-overs.exp: displaced=off: signal thr3: continue to sigusr1_handler
For good measure, I made the test try displaced stepping too. And
then I found it crashes GDB on x86-64 (a hardware step target), but
only when displaced stepping... :
KFAIL: gdb.threads/multiple-step-overs.exp: displaced=on: signal thr1: continue to sigusr1_handler (PRMS: gdb/18216)
KFAIL: gdb.threads/multiple-step-overs.exp: displaced=on: signal thr2: continue to sigusr1_handler (PRMS: gdb/18216)
KFAIL: gdb.threads/multiple-step-overs.exp: displaced=on: signal thr3: continue to sigusr1_handler (PRMS: gdb/18216)
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x000000000062a83a in process_event_stop_test (ecs=0x7fff847eeee0) at src/gdb/infrun.c:4964
4964 if (sr_bp->loc->permanent
Setting up the environment for debugging gdb.
Breakpoint 1 at 0x79fcfc: file src/gdb/common/errors.c, line 54.
Breakpoint 2 at 0x50a26c: file src/gdb/cli/cli-cmds.c, line 217.
(top-gdb) p sr_bp
$1 = (struct breakpoint *) 0x0
(top-gdb) bt
#0 0x000000000062a83a in process_event_stop_test (ecs=0x7fff847eeee0) at src/gdb/infrun.c:4964
#1 0x000000000062a1af in handle_signal_stop (ecs=0x7fff847eeee0) at src/gdb/infrun.c:4715
#2 0x0000000000629097 in handle_inferior_event (ecs=0x7fff847eeee0) at src/gdb/infrun.c:4165
#3 0x0000000000627482 in fetch_inferior_event (client_data=0x0) at src/gdb/infrun.c:3298
#4 0x000000000064ad7b in inferior_event_handler (event_type=INF_REG_EVENT, client_data=0x0) at src/gdb/inf-loop.c:56
#5 0x00000000004c375f in handle_target_event (error=0, client_data=0x0) at src/gdb/linux-nat.c:4658
#6 0x0000000000648c47 in handle_file_event (file_ptr=0x2e0eaa0, ready_mask=1) at src/gdb/event-loop.c:658
The all-stop-non-stop series fixes this, but meanwhile, this augments
the multiple-step-overs.exp test to cover this, KFAILed.
gdb/testsuite/ChangeLog:
2015-04-08 Pedro Alves <palves@redhat.com>
PR gdb/18214
PR gdb/18216
* gdb.threads/multiple-step-overs.c (sigusr1_handler): New
function.
(main): Install it as SIGUSR1 handler.
* gdb.threads/multiple-step-overs.exp (setup): Remove 'prefix'
parameter. Always use "setup" as prefix. Toggle "set
displaced-stepping" off/on depending on global. Don't switch to
thread 1 here.
(top level): Add displaced stepping "off/on" test axis. Update
"setup" calls. Wrap each subtest with with_test_prefix. Test
continuing with a queued signal in each thread.
---
gdb/testsuite/ChangeLog | 15 +++++
gdb/testsuite/gdb.threads/multiple-step-overs.c | 7 ++
gdb/testsuite/gdb.threads/multiple-step-overs.exp | 80 +++++++++++++++++++----
3 files changed, 88 insertions(+), 14 deletions(-)
Comments
Pedro Alves <palves@redhat.com> writes:
> For good measure, I made the test try displaced stepping too. And
> then I found it crashes GDB on x86-64 (a hardware step target), but
> only when displaced stepping... :
Turning displaced stepping on also exposes some problems on arm-linux
too, besides these two kfails, there are also:
FAIL: gdb.threads/multiple-step-overs.exp: displaced=on: step: step
FAIL: gdb.threads/multiple-step-overs.exp: displaced=on: next: next
FAIL: gdb.threads/multiple-step-overs.exp: displaced=on: continue: continue
FAIL: gdb.threads/multiple-step-overs.exp: displaced=on: signal thr1: continue to sigusr1_handler
step^M
[Switching to Thread 30857]^M
^M
Breakpoint 4, child_function_2 (arg=0x0) at /home/yao/SourceCode/gnu/gdb/git/gdb/testsuite/gdb.threads/multiple-step-overs.c:66^M
66 callme (); /* set breakpoint thread 2 here */^M
(gdb) FAIL: gdb.threads/multiple-step-overs.exp: displaced=on: step: step
next^M
[Switching to Thread 30941]^M
^M
Breakpoint 4, child_function_2 (arg=0x0) at /home/yao/SourceCode/gnu/gdb/git/gdb/testsuite/gdb.threads/multiple-step-overs.c:66^M
66 callme (); /* set breakpoint thread 2 here */^M
(gdb) FAIL: gdb.threads/multiple-step-overs.exp: displaced=on: next: next
I'll analyse them tomorrow.
@@ -1,5 +1,20 @@
2015-04-08 Pedro Alves <palves@redhat.com>
+ PR gdb/18214
+ PR gdb/18216
+ * gdb.threads/multiple-step-overs.c (sigusr1_handler): New
+ function.
+ (main): Install it as SIGUSR1 handler.
+ * gdb.threads/multiple-step-overs.exp (setup): Remove 'prefix'
+ parameter. Always use "setup" as prefix. Toggle "set
+ displaced-stepping" off/on depending on global. Don't switch to
+ thread 1 here.
+ (top level): Add displaced stepping "off/on" test axis. Update
+ "setup" calls. Wrap each subtest with with_test_prefix. Test
+ continuing with a queued signal in each thread.
+
+2015-04-08 Pedro Alves <palves@redhat.com>
+
* gdb.trace/actions.exp: Use gdb_load before gdb_run_cmd.
* gdb.trace/infotrace.exp: Use gdb_load before gdb_run_cmd. Use
gdb_breakpoint instead of gdb_test that doesn't expect anything.
@@ -26,6 +26,11 @@ pthread_barrier_t barrier;
pthread_t child_thread_2, child_thread_3;
void
+sigusr1_handler (int signo)
+{
+}
+
+void
callme (void)
{
}
@@ -76,6 +81,8 @@ main ()
int res;
long i;
+ signal (SIGUSR1, sigusr1_handler);
+
/* Call these early so that PLTs for these are resolved soon,
instead of in the threads. RTLD_NOW should work as well. */
usleep (0);
@@ -29,19 +29,21 @@ if {[gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" \
return -1
}
-# Prepare environment for test. PREFIX is used as prefix in test
-# messages.
+# Prepare environment for test.
-proc setup { prefix } {
+proc setup {} {
global executable
+ global displaced
- with_test_prefix $prefix {
+ with_test_prefix "setup" {
clean_restart $executable
if ![runto_main] {
return -1
}
+ gdb_test_no_output "set displaced-stepping $displaced"
+
gdb_breakpoint [gdb_get_line_number "set wait-threads breakpoint here"]
gdb_continue_to_breakpoint "run to breakpoint"
gdb_test "info threads" "3 .* 2 .*\\\* 1.*" "info threads shows all threads"
@@ -59,8 +61,7 @@ proc setup { prefix } {
gdb_continue_to_breakpoint "run to breakpoint in thread 2"
gdb_test "p *myp = 0" " = 0" "unbreak loop in thread 2"
- # Switch back to thread 1 and disable scheduler locking.
- gdb_test "thread 1" "Switching.*"
+ # Disable scheduler locking.
gdb_test_no_output "set scheduler-locking off"
# Now all 3 threads are stopped for a breakpoint that needs to
@@ -68,13 +69,64 @@ proc setup { prefix } {
}
}
-setup "step"
-gdb_test "step" "in wait_threads .*"
+foreach displaced { "off" "on" } {
+ with_test_prefix "displaced=$displaced" {
+ with_test_prefix "step" {
+ setup
+ gdb_test "thread 1" "Switching.*"
+ gdb_test "step" "in wait_threads .*"
+ }
+
+ with_test_prefix "next" {
+ setup
+ gdb_test "thread 1" "Switching.*"
+ gdb_test "next" "pthread_join.*"
+ }
-setup "next"
-gdb_test "set debug infrun 1" ".*"
-gdb_test "next" "pthread_join.*"
+ with_test_prefix "continue" {
+ setup
+ gdb_breakpoint [gdb_get_line_number "EXIT_SUCCESS"]
+ gdb_test "thread 1" "Switching.*"
+ gdb_test "continue" "EXIT_SUCCESS.*"
+ }
-setup "continue"
-gdb_breakpoint [gdb_get_line_number "EXIT_SUCCESS"]
-gdb_test "continue" "EXIT_SUCCESS.*"
+ # Try continuing with a queued signal in each of the threads
+ # (one at a time). Should stop at the signal handler, instead
+ # of re-trapping the breakpoint the threads were already
+ # stopped at.
+ foreach thread {1 2 3} {
+ with_test_prefix "signal thr$thread" {
+ setup
+
+ # Queue a signal in THREAD.
+ gdb_test "thread $thread" "Switching.*"
+ gdb_test_no_output "queue-signal SIGUSR1"
+
+ # Switch back to thread 1, and continue.
+ gdb_test "thread 1" "Switching.*" "switch back to thread 1"
+ gdb_breakpoint "sigusr1_handler" "set break at sigusr1_handler"
+
+ set msg "continue to sigusr1_handler"
+ gdb_test_multiple "continue" $msg {
+ -re "Breakpoint .* sigusr1_handler .*$gdb_prompt $" {
+ pass $msg
+ }
+ -re "Breakpoint .*$gdb_prompt $" {
+ if {![can_single_step_to_signal_handler]
+ && $thread != 1 && $displaced == "off"} {
+ setup_kfail "gdb/18214" "*-*-*"
+ }
+ fail $msg
+ }
+ eof {
+ if {[can_single_step_to_signal_handler]
+ && $displaced == "on"} {
+ setup_kfail "gdb/18216" "*-*-*"
+ }
+ fail $msg
+ }
+ }
+ }
+ }
+ }
+}