This patch fixes a GDBserver crash when one thread is stepping over
a syscall instruction which is exit. Step-over isn't finished due
to the exit, but GDBserver doesn't clean up the state of step-over,
so in the wait next time, GDBserver will wait on step_over_bkpt,
which is already exited, and GDBserver crashes because
'requested_child' is NULL. See gdbserver logs below,
Need step over [LWP 14858]? yes, found breakpoint at 0x2aaaaad91307^M
proceed_all_lwps: found thread 14858 needing a step-over^M
Starting step-over on LWP 14858. Stopping all threads^M
>>>> entering void stop_all_lwps(int, lwp_info*)
....
<<<< exiting void stop_all_lwps(int, lwp_info*)^M
Done stopping all threads for step-over.^M
pc is 0x2aaaaad91307^M
Writing 0f to 0x2aaaaad91307 in process 14858^M
Could not find fast tracepoint jump at 0x2aaaaad91307 in list (uninserting).^M
pending reinsert at 0x2aaaaad91307^M
step from pc 0x2aaaaad91307^M
Resuming lwp 14858 (step, signal 0, stop not expected)^M
# but step_over_bkpt is still LWP 14858, which is wrong
The fix is to finish step-over if it is ongoing, and unsuspend other
threads. Without the fix in linux-low.c, GDBserver will crash in
with running gdb.base/step-over-exit.exp.
gdb/gdbserver:
2016-06-17 Yao Qi <yao.qi@linaro.org>
* linux-low.c (unsuspend_all_lwps): Declare.
(linux_low_filter_event): If thread exited, call finish_step_over.
If step-over is finished, unsuspend other threads.