Delete reinsert breakpoints from forked child

When a thread is stepping over a syscall instruction with software
single step, GDBserver inserts reinsert breakpoints at the next pcs.
If the syscall call is fork, the forked child has reinsert breakpoint
in its space, and GDBserver clones parent's breakpoint list to child's.
When GDBserver resumes the child, its bp_reinsert is zero, but has
reinsert breakpoints, so the following assert is triggered if I apply
the patch extending step-over-syscall.exp.

gdb/gdbserver/linux-low.c:4292: A problem internal to GDBserver has been detected.^M
void linux_resume_one_lwp_throw(lwp_info*, int, int, siginfo_t*): Assertion `!has_reinsert_breakpoints (proc)' failed.

gdb/gdbserver:

2016-06-17  Yao Qi  <yao.qi@linaro.org>

	* linux-low.c (handle_extended_wait): If the parent is doing
	step-over, remove the reinsert breakpoints from the forked child.

2 files changed, 26 insertions, 0 deletions

diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index fd70f59..734d70d 100644
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,5 +1,10 @@
 2016-06-17  Yao Qi  <yao.qi@linaro.org>
 
+	* linux-low.c (handle_extended_wait): If the parent is doing
+	step-over, remove the reinsert breakpoints from the forked child.
+
+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.
diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index 95104d2..3f2d08e 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -569,6 +569,27 @@ handle_extended_wait (struct lwp_info **orig_event_lwp, int wstat)
 	  event_lwp->status_pending_p = 1;
 	  event_lwp->status_pending = wstat;
 
+	  /* If the parent thread is doing step-over with reinsert
+	     breakpoints, the reinsert breakpoints are still in forked
+	     child's process space and cloned to its breakpoint list
+	     from the parent's.  Remove them from the child process.  */
+	  if (event_lwp->bp_reinsert != 0
+	      && can_software_single_step ()
+	      && event == PTRACE_EVENT_FORK)
+	    {
+	      struct thread_info *saved_thread = current_thread;
+
+	      /* The child process is forked and stopped, so it is safe
+		 to access its memory without stopping all other threads
+		 from other processes.  */
+	      current_thread = child_thr;
+	      delete_reinsert_breakpoints ();
+	      current_thread = saved_thread;
+
+	      gdb_assert (has_reinsert_breakpoints (parent_proc));
+	      gdb_assert (!has_reinsert_breakpoints (child_proc));
+	    }
+
 	  /* Report the event.  */
 	  return 0;
 	}