+ return (lp->stopped == 0 || (lp->status != 0 && lp->resumed));
+}
+
+/* Count the LWP's that have had events. */
+
+static int
+count_events_callback (struct lwp_info *lp, void *data)
+{
+ int *count = data;
+
+ gdb_assert (count != NULL);
+
+ /* Count only LWPs that have a SIGTRAP event pending. */
+ if (lp->status != 0
+ && WIFSTOPPED (lp->status) && WSTOPSIG (lp->status) == SIGTRAP)
+ (*count)++;
+
+ return 0;
+}
+
+/* Select the LWP (if any) that is currently being single-stepped. */
+
+static int
+select_singlestep_lwp_callback (struct lwp_info *lp, void *data)
+{
+ if (lp->step && lp->status != 0)
+ return 1;
+ else
+ return 0;
+}
+
+/* Select the Nth LWP that has had a SIGTRAP event. */
+
+static int
+select_event_lwp_callback (struct lwp_info *lp, void *data)
+{
+ int *selector = data;
+
+ gdb_assert (selector != NULL);
+
+ /* Select only LWPs that have a SIGTRAP event pending. */
+ if (lp->status != 0
+ && WIFSTOPPED (lp->status) && WSTOPSIG (lp->status) == SIGTRAP)
+ if ((*selector)-- == 0)
+ return 1;
+
+ return 0;
+}
+
+static int
+cancel_breakpoints_callback (struct lwp_info *lp, void *data)
+{
+ struct lwp_info *event_lp = data;
+
+ /* Leave the LWP that has been elected to receive a SIGTRAP alone. */
+ if (lp == event_lp)
+ return 0;
+
+ /* If a LWP other than the LWP that we're reporting an event for has
+ hit a GDB breakpoint (as opposed to some random trap signal),
+ then just arrange for it to hit it again later. We don't keep
+ the SIGTRAP status and don't forward the SIGTRAP signal to the
+ LWP. We will handle the current event, eventually we will resume
+ all LWPs, and this one will get its breakpoint trap again.
+
+ If we do not do this, then we run the risk that the user will
+ delete or disable the breakpoint, but the LWP will have already
+ tripped on it. */
+
+ if (lp->status != 0
+ && WIFSTOPPED (lp->status) && WSTOPSIG (lp->status) == SIGTRAP
+ && breakpoint_inserted_here_p (read_pc_pid (lp->ptid) -
+ DECR_PC_AFTER_BREAK))
+ {
+ if (debug_lin_lwp)
+ fprintf_unfiltered (gdb_stdlog,
+ "CBC: Push back breakpoint for %s\n",
+ target_pid_to_str (lp->ptid));
+
+ /* Back up the PC if necessary. */
+ if (DECR_PC_AFTER_BREAK)
+ write_pc_pid (read_pc_pid (lp->ptid) - DECR_PC_AFTER_BREAK, lp->ptid);
+
+ /* Throw away the SIGTRAP. */
+ lp->status = 0;
+ }
+
+ return 0;
+}
+
+/* Select one LWP out of those that have events pending. */
+
+static void
+select_event_lwp (struct lwp_info **orig_lp, int *status)
+{
+ int num_events = 0;
+ int random_selector;
+ struct lwp_info *event_lp;
+
+ /* Record the wait status for the origional LWP. */
+ (*orig_lp)->status = *status;
+
+ /* Give preference to any LWP that is being single-stepped. */
+ event_lp = iterate_over_lwps (select_singlestep_lwp_callback, NULL);
+ if (event_lp != NULL)
+ {
+ if (debug_lin_lwp)
+ fprintf_unfiltered (gdb_stdlog,
+ "SEL: Select single-step %s\n",
+ target_pid_to_str (event_lp->ptid));
+ }
+ else
+ {
+ /* No single-stepping LWP. Select one at random, out of those
+ which have had SIGTRAP events. */
+
+ /* First see how many SIGTRAP events we have. */
+ iterate_over_lwps (count_events_callback, &num_events);
+
+ /* Now randomly pick a LWP out of those that have had a SIGTRAP. */
+ random_selector = (int)
+ ((num_events * (double) rand ()) / (RAND_MAX + 1.0));
+
+ if (debug_lin_lwp && num_events > 1)
+ fprintf_unfiltered (gdb_stdlog,
+ "SEL: Found %d SIGTRAP events, selecting #%d\n",
+ num_events, random_selector);
+
+ event_lp = iterate_over_lwps (select_event_lwp_callback,
+ &random_selector);
+ }
+
+ if (event_lp != NULL)
+ {
+ /* Switch the event LWP. */
+ *orig_lp = event_lp;
+ *status = event_lp->status;
+ }
+
+ /* Flush the wait status for the event LWP. */
+ (*orig_lp)->status = 0;
+}
+
+/* Return non-zero if LP has been resumed. */
+
+static int
+resumed_callback (struct lwp_info *lp, void *data)
+{
+ return lp->resumed;
+}
+
+#ifdef CHILD_WAIT
+
+/* We need to override child_wait to support attaching to cloned
+ processes, since a normal wait (as done by the default version)
+ ignores those processes. */
+
+/* Wait for child PTID to do something. Return id of the child,
+ minus_one_ptid in case of error; store status into *OURSTATUS. */
+
+ptid_t
+child_wait (ptid_t ptid, struct target_waitstatus *ourstatus)
+{
+ int save_errno;
+ int status;
+ pid_t pid;
+
+ do
+ {
+ set_sigint_trap (); /* Causes SIGINT to be passed on to the
+ attached process. */
+ set_sigio_trap ();
+
+ pid = waitpid (GET_PID (ptid), &status, 0);
+ if (pid == -1 && errno == ECHILD)
+ /* Try again with __WCLONE to check cloned processes. */
+ pid = waitpid (GET_PID (ptid), &status, __WCLONE);
+
+ if (debug_lin_lwp)
+ {
+ fprintf_unfiltered (gdb_stdlog,
+ "CW: waitpid %ld received %s\n",
+ (long) pid, status_to_str (status));
+ }
+
+ save_errno = errno;
+
+ /* Make sure we don't report an event for the exit of the
+ original program, if we've detached from it. */
+ if (pid != -1 && !WIFSTOPPED (status) && pid != GET_PID (inferior_ptid))
+ {
+ pid = -1;
+ save_errno = EINTR;
+ }
+
+ /* Check for stop events reported by a process we didn't already
+ know about - in this case, anything other than inferior_ptid.
+
+ If we're expecting to receive stopped processes after fork,
+ vfork, and clone events, then we'll just add the new one to
+ our list and go back to waiting for the event to be reported
+ - the stopped process might be returned from waitpid before
+ or after the event is. If we want to handle debugging of
+ CLONE_PTRACE processes we need to do more here, i.e. switch
+ to multi-threaded mode. */
+ if (pid != -1 && WIFSTOPPED (status) && WSTOPSIG (status) == SIGSTOP
+ && pid != GET_PID (inferior_ptid))
+ {
+ linux_record_stopped_pid (pid);
+ pid = -1;
+ save_errno = EINTR;
+ }
+
+ clear_sigio_trap ();
+ clear_sigint_trap ();
+ }
+ while (pid == -1 && save_errno == EINTR);
+
+ if (pid == -1)
+ {
+ warning ("Child process unexpectedly missing: %s",
+ safe_strerror (errno));
+
+ /* Claim it exited with unknown signal. */
+ ourstatus->kind = TARGET_WAITKIND_SIGNALLED;
+ ourstatus->value.sig = TARGET_SIGNAL_UNKNOWN;
+ return minus_one_ptid;
+ }
+
+ /* Handle GNU/Linux's extended waitstatus for trace events. */
+ if (WIFSTOPPED (status) && WSTOPSIG (status) == SIGTRAP && status >> 16 != 0)
+ return linux_handle_extended_wait (pid, status, ourstatus);
+
+ store_waitstatus (ourstatus, status);
+ return pid_to_ptid (pid);
+}
+
+#endif
+
+/* Stop an active thread, verify it still exists, then resume it. */
+
+static int
+stop_and_resume_callback (struct lwp_info *lp, void *data)
+{
+ struct lwp_info *ptr;
+
+ if (!lp->stopped && !lp->signalled)
+ {
+ stop_callback (lp, NULL);
+ stop_wait_callback (lp, NULL);
+ /* Resume if the lwp still exists. */
+ for (ptr = lwp_list; ptr; ptr = ptr->next)
+ if (lp == ptr)
+ {
+ resume_callback (lp, NULL);
+ resume_set_callback (lp, NULL);
+ }
+ }
+ return 0;