[v2] gdb: fix an issue with thread list corruption
Commit Message
When resuming a target in non-stop mode with 'c -a', the continue command
uses for_each_thread() to proceed each stopped thread individually. This
uses an all_threads_safe() iteration.
If one of the stopped threads does an inline step-over, since the target
is non-stop, we stop_all_threads(), which involves update_thread_list(),
which, in turn, may delete_thread().
If this deleted the thread pointed to by the m_next safe iterator member,
the above all_threads_safe() iteration will be corrupted.
The thread we're proceeding is stopped and there is no reason to delete
it. Consequently, there is no reason for all_threads_safe(), which isn't
that safe in this scenario.
Iterate using all_threads() and inline proceed_thread_callback().
CC: Simon Marchi <simark@simark.ca>
---
gdb/infcmd.c | 53 ++++++++++++++++++++++++++--------------------------
1 file changed, 27 insertions(+), 26 deletions(-)
@@ -685,29 +685,6 @@ starti_command (const char *args, int from_tty)
run_command_1 (args, from_tty, RUN_STOP_AT_FIRST_INSN);
}
-static void
-proceed_thread_callback (struct thread_info *thread)
-{
- /* We go through all threads individually instead of compressing
- into a single target `resume_all' request, because some threads
- may be stopped in internal breakpoints/events, or stopped waiting
- for its turn in the displaced stepping queue (that is, they are
- running from the user's perspective but internally stopped). The
- target side has no idea about why the thread is stopped, so a
- `resume_all' command would resume too much. If/when GDB gains a
- way to tell the target `hold this thread stopped until I say
- otherwise', then we can optimize this. */
- if (thread->state () != THREAD_STOPPED)
- return;
-
- if (!thread->inf->has_execution ())
- return;
-
- switch_to_thread (thread);
- clear_proceed_status (0);
- proceed ((CORE_ADDR) -1, GDB_SIGNAL_DEFAULT);
-}
-
static void
ensure_valid_thread (void)
{
@@ -746,12 +723,12 @@ ensure_not_running (void)
}
void
-continue_1 (int all_threads)
+continue_1 (int all)
{
ERROR_NO_INFERIOR;
ensure_not_tfind_mode ();
- if (non_stop && all_threads)
+ if (non_stop && all)
{
/* Don't error out if the current thread is running, because
there may be other stopped threads. */
@@ -762,7 +739,31 @@ continue_1 (int all_threads)
scoped_disable_commit_resumed disable_commit_resumed
("continue all threads in non-stop");
- for_each_thread (proceed_thread_callback);
+ /* Do not use all_threads_safe, because it's possible for the next
+ thread to get removed while resuming THREAD. We know that thread
+ is stopped and should not disappear under our feet. */
+ for (thread_info &thread : all_threads ())
+ {
+ /* We go through all threads individually instead of compressing
+ into a single target `resume_all' request, because some
+ threads may be stopped in internal breakpoints/events, or
+ stopped waiting for its turn in the displaced stepping queue
+ (that is, they are running from the user's perspective but
+ internally stopped). The target side has no idea about why
+ the thread is stopped, so a `resume_all' command would resume
+ too much. If/when GDB gains a way to tell the target `hold
+ this thread stopped until I say otherwise', then we can
+ optimize this. */
+ if (thread.state () != THREAD_STOPPED)
+ continue;
+
+ if (!thread.inf->has_execution ())
+ continue;
+
+ switch_to_thread (&thread);
+ clear_proceed_status (0);
+ proceed ((CORE_ADDR) -1, GDB_SIGNAL_DEFAULT);
+ }
if (current_ui->prompt_state == PROMPT_BLOCKED)
{