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[binutils-gdb] follow-exec: delete all non-execing threads
- From: Pedro Alves <palves at sourceware dot org>
- To: gdb-cvs at sourceware dot org
- Date: 3 Mar 2015 01:32:43 -0000
- Subject: [binutils-gdb] follow-exec: delete all non-execing threads
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=95e50b2723eba05ca34e9ea69c1de63e65ce9578
commit 95e50b2723eba05ca34e9ea69c1de63e65ce9578
Author: Pedro Alves <palves@redhat.com>
Date: Tue Mar 3 01:25:17 2015 +0000
follow-exec: delete all non-execing threads
This fixes invalid reads Valgrind first caught when debugging against
a GDBserver patched with a series that adds exec events to the remote
protocol. Like these, using the gdb.threads/thread-execl.exp test:
$ valgrind ./gdb -data-directory=data-directory ./testsuite/gdb.threads/thread-execl -ex "tar extended-remote :9999" -ex "b thread_execler" -ex "c" -ex "set scheduler-locking on"
...
Breakpoint 1, thread_execler (arg=0x0) at src/gdb/testsuite/gdb.threads/thread-execl.c:29
29 if (execl (image, image, NULL) == -1)
(gdb) n
Thread 32509.32509 is executing new program: build/gdb/testsuite/gdb.threads/thread-execl
[New Thread 32509.32532]
==32510== Invalid read of size 4
==32510== at 0x5AA7D8: delete_breakpoint (breakpoint.c:13989)
==32510== by 0x6285D3: delete_thread_breakpoint (thread.c:100)
==32510== by 0x628603: delete_step_resume_breakpoint (thread.c:109)
==32510== by 0x61622B: delete_thread_infrun_breakpoints (infrun.c:2928)
==32510== by 0x6162EF: for_each_just_stopped_thread (infrun.c:2958)
==32510== by 0x616311: delete_just_stopped_threads_infrun_breakpoints (infrun.c:2969)
==32510== by 0x616C96: fetch_inferior_event (infrun.c:3267)
==32510== by 0x63A2DE: inferior_event_handler (inf-loop.c:57)
==32510== by 0x4E0E56: remote_async_serial_handler (remote.c:11877)
==32510== by 0x4AF620: run_async_handler_and_reschedule (ser-base.c:137)
==32510== by 0x4AF6F0: fd_event (ser-base.c:182)
==32510== by 0x63806D: handle_file_event (event-loop.c:762)
==32510== Address 0xcf333e0 is 16 bytes inside a block of size 200 free'd
==32510== at 0x4A07577: free (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==32510== by 0x77CB74: xfree (common-utils.c:98)
==32510== by 0x5AA954: delete_breakpoint (breakpoint.c:14056)
==32510== by 0x5988BD: update_breakpoints_after_exec (breakpoint.c:3765)
==32510== by 0x61360F: follow_exec (infrun.c:1091)
==32510== by 0x6186FA: handle_inferior_event (infrun.c:4061)
==32510== by 0x616C55: fetch_inferior_event (infrun.c:3261)
==32510== by 0x63A2DE: inferior_event_handler (inf-loop.c:57)
==32510== by 0x4E0E56: remote_async_serial_handler (remote.c:11877)
==32510== by 0x4AF620: run_async_handler_and_reschedule (ser-base.c:137)
==32510== by 0x4AF6F0: fd_event (ser-base.c:182)
==32510== by 0x63806D: handle_file_event (event-loop.c:762)
==32510==
[Switching to Thread 32509.32532]
Breakpoint 1, thread_execler (arg=0x0) at src/gdb/testsuite/gdb.threads/thread-execl.c:29
29 if (execl (image, image, NULL) == -1)
(gdb)
The breakpoint in question is the step-resume breakpoint of the
non-main thread, the one that was "next"ed.
The exact same issue can be seen on mainline with native debugging, by
running the thread-execl.exp test in non-stop mode, because the kernel
doesn't report a thread exit event for the execing thread.
Tested on x86_64 Fedora 20.
gdb/ChangeLog:
2015-03-02 Pedro Alves <palves@redhat.com>
* infrun.c (follow_exec): Delete all threads of the process except
the event thread. Extended comments.
gdb/testsuite/ChangeLog:
2015-03-02 Pedro Alves <palves@redhat.com>
* gdb.threads/thread-execl.exp (do_test): Handle non-stop.
(top level): Call do_test with non-stop as well.
Diff:
---
gdb/ChangeLog | 5 ++++
gdb/infrun.c | 48 ++++++++++++++++++++++--------
gdb/testsuite/ChangeLog | 5 ++++
gdb/testsuite/gdb.threads/thread-execl.exp | 24 +++++++++++++--
4 files changed, 67 insertions(+), 15 deletions(-)
diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 922b1d9..68c55c1 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2015-03-02 Pedro Alves <palves@redhat.com>
+
+ * infrun.c (follow_exec): Delete all threads of the process except
+ the event thread. Extended comments.
+
2015-03-02 Joel Brobecker <brobecker@adacore.com>
* contrib/ari/gdb_ari.sh: Reinstate checks for "true" and "false".
diff --git a/gdb/infrun.c b/gdb/infrun.c
index 15589b6..f87ed4c 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -1060,10 +1060,11 @@ show_follow_exec_mode_string (struct ui_file *file, int from_tty,
/* EXECD_PATHNAME is assumed to be non-NULL. */
static void
-follow_exec (ptid_t pid, char *execd_pathname)
+follow_exec (ptid_t ptid, char *execd_pathname)
{
- struct thread_info *th = inferior_thread ();
+ struct thread_info *th, *tmp;
struct inferior *inf = current_inferior ();
+ int pid = ptid_get_pid (ptid);
/* This is an exec event that we actually wish to pay attention to.
Refresh our symbol table to the newly exec'd program, remove any
@@ -1088,24 +1089,47 @@ follow_exec (ptid_t pid, char *execd_pathname)
mark_breakpoints_out ();
- update_breakpoints_after_exec ();
-
- /* If there was one, it's gone now. We cannot truly step-to-next
- statement through an exec(). */
+ /* The target reports the exec event to the main thread, even if
+ some other thread does the exec, and even if the main thread was
+ stopped or already gone. We may still have non-leader threads of
+ the process on our list. E.g., on targets that don't have thread
+ exit events (like remote); or on native Linux in non-stop mode if
+ there were only two threads in the inferior and the non-leader
+ one is the one that execs (and nothing forces an update of the
+ thread list up to here). When debugging remotely, it's best to
+ avoid extra traffic, when possible, so avoid syncing the thread
+ list with the target, and instead go ahead and delete all threads
+ of the process but one that reported the event. Note this must
+ be done before calling update_breakpoints_after_exec, as
+ otherwise clearing the threads' resources would reference stale
+ thread breakpoints -- it may have been one of these threads that
+ stepped across the exec. We could just clear their stepping
+ states, but as long as we're iterating, might as well delete
+ them. Deleting them now rather than at the next user-visible
+ stop provides a nicer sequence of events for user and MI
+ notifications. */
+ ALL_NON_EXITED_THREADS_SAFE (th, tmp)
+ if (ptid_get_pid (th->ptid) == pid && !ptid_equal (th->ptid, ptid))
+ delete_thread (th->ptid);
+
+ /* We also need to clear any left over stale state for the
+ leader/event thread. E.g., if there was any step-resume
+ breakpoint or similar, it's gone now. We cannot truly
+ step-to-next statement through an exec(). */
+ th = inferior_thread ();
th->control.step_resume_breakpoint = NULL;
th->control.exception_resume_breakpoint = NULL;
th->control.single_step_breakpoints = NULL;
th->control.step_range_start = 0;
th->control.step_range_end = 0;
- /* The target reports the exec event to the main thread, even if
- some other thread does the exec, and even if the main thread was
- already stopped --- if debugging in non-stop mode, it's possible
- the user had the main thread held stopped in the previous image
- --- release it now. This is the same behavior as step-over-exec
- with scheduler-locking on in all-stop mode. */
+ /* The user may have had the main thread held stopped in the
+ previous image (e.g., schedlock on, or non-stop). Release
+ it now. */
th->stop_requested = 0;
+ update_breakpoints_after_exec ();
+
/* What is this a.out's name? */
printf_unfiltered (_("%s is executing new program: %s\n"),
target_pid_to_str (inferior_ptid),
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 76ed5e2..3b7bf7d 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,5 +1,10 @@
2015-03-02 Pedro Alves <palves@redhat.com>
+ * gdb.threads/thread-execl.exp (do_test): Handle non-stop.
+ (top level): Call do_test with non-stop as well.
+
+2015-03-02 Pedro Alves <palves@redhat.com>
+
* lib/gdb.exp (gdb_test_multiple) <internal error>: Set result to
-1.
diff --git a/gdb/testsuite/gdb.threads/thread-execl.exp b/gdb/testsuite/gdb.threads/thread-execl.exp
index 4a8016c..a598ad0 100644
--- a/gdb/testsuite/gdb.threads/thread-execl.exp
+++ b/gdb/testsuite/gdb.threads/thread-execl.exp
@@ -34,9 +34,18 @@ if {[gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" \
proc do_test { schedlock } {
global binfile
- with_test_prefix "schedlock $schedlock" {
+ if {$schedlock == "non-stop"} {
+ set prefix $schedlock
+ } else {
+ set prefix "schedlock $schedlock"
+ }
+ with_test_prefix "$prefix" {
clean_restart ${binfile}
+ if {$schedlock == "non-stop"} {
+ gdb_test_no_output "set non-stop 1"
+ }
+
if ![runto_main] {
return 0
}
@@ -45,16 +54,25 @@ proc do_test { schedlock } {
gdb_breakpoint "thread_execler"
gdb_test "continue" ".*thread_execler.*" "continue to thread start"
+ if {$schedlock == "non-stop"} {
+ gdb_test "thread 2" \
+ "Switching to .*thread_execler.*" \
+ "switch to event thread"
+ }
+
# Now set a breakpoint at `main', and step over the execl call. The
# breakpoint at main should be reached. GDB should not try to revert
# back to the old thread from the old image and resume stepping it
# (since it is gone).
gdb_breakpoint "main"
- gdb_test_no_output "set scheduler-locking $schedlock"
+
+ if {$schedlock != "non-stop"} {
+ gdb_test_no_output "set scheduler-locking $schedlock"
+ }
gdb_test "next" ".*main.*" "get to main in new image"
}
}
-foreach schedlock {"off" "step" "on"} {
+foreach schedlock {"off" "step" "on" "non-stop"} {
do_test $schedlock
}