gdbserver: Hide and don't detach pending clone children

This commit extends the logic added by these two commits from a while
ago:

 #1  7b961964f866  (gdbserver: hide fork child threads from GDB),
 #2  df5ad102009c  (gdb, gdbserver: detach fork child when detaching from fork parent)

... to handle thread clone events, which are very similar to (v)fork
events.

For #1, we want to hide clone children as well, so just update the
comments.

For #2, unlike (v)fork children, pending clone children aren't full
processes, they're just threads, so don't detach them in
handle_detach.  linux-low.cc will take care of detaching them along
with all other threads of the process, there's nothing special that
needs to be done.

Change-Id: I7f5901d07efda576a2522d03e183994e071b8ffc

5 files changed, 40 insertions, 31 deletions

diff --git a/gdbserver/linux-low.cc b/gdbserver/linux-low.cc
index 895583e2a6d..3a95d820cde 100644
--- a/gdbserver/linux-low.cc
+++ b/gdbserver/linux-low.cc
@@ -6874,9 +6874,10 @@ linux_process_target::thread_pending_parent (thread_info *thread)
 }
 
 thread_info *
-linux_process_target::thread_pending_child (thread_info *thread)
+linux_process_target::thread_pending_child (thread_info *thread,
+					    target_waitkind *kind)
 {
-  lwp_info *child = get_thread_lwp (thread)->pending_child ();
+  lwp_info *child = get_thread_lwp (thread)->pending_child (kind);
 
   if (child == nullptr)
     return nullptr;
diff --git a/gdbserver/linux-low.h b/gdbserver/linux-low.h
index c81b93f1171..e7237bba3b3 100644
--- a/gdbserver/linux-low.h
+++ b/gdbserver/linux-low.h
@@ -313,7 +313,8 @@ public:
 #endif
 
   thread_info *thread_pending_parent (thread_info *thread) override;
-  thread_info *thread_pending_child (thread_info *thread) override;
+  thread_info *thread_pending_child (thread_info *thread,
+				     target_waitkind *kind) override;
 
   bool supports_catch_syscall () override;
 
@@ -732,8 +733,8 @@ struct pending_signal
 
 struct lwp_info
 {
-  /* If this LWP is a fork child that wasn't reported to GDB yet, return
-     its parent, else nullptr.  */
+  /* If this LWP is a fork/vfork/clone child that wasn't reported to
+     GDB yet, return its parent, else nullptr.  */
   lwp_info *pending_parent () const
   {
     if (this->fork_relative == nullptr)
@@ -741,10 +742,10 @@ struct lwp_info
 
     gdb_assert (this->fork_relative->fork_relative == this);
 
-    /* In a fork parent/child relationship, the parent has a status pending and
-       the child does not, and a thread can only be in one such relationship
-       at most.  So we can recognize who is the parent based on which one has
-       a pending status.  */
+    /* In a parent/child relationship, the parent has a status pending
+       and the child does not, and a thread can only be in one such
+       relationship at most.  So we can recognize who is the parent
+       based on which one has a pending status.  */
     gdb_assert (!!this->status_pending_p
 		!= !!this->fork_relative->status_pending_p);
 
@@ -754,24 +755,25 @@ struct lwp_info
     const target_waitstatus &ws
       = this->fork_relative->waitstatus;
     gdb_assert (ws.kind () == TARGET_WAITKIND_FORKED
-		|| ws.kind () == TARGET_WAITKIND_VFORKED);
+		|| ws.kind () == TARGET_WAITKIND_VFORKED
+		|| ws.kind () == TARGET_WAITKIND_THREAD_CLONED);
 
     return this->fork_relative;
   }
 
-  /* If this LWP is the parent of a fork child we haven't reported to GDB yet,
-     return that child, else nullptr.  */
-  lwp_info *pending_child () const
+  /* If this LWP is the parent of a fork/vfork/clone child we haven't
+     reported to GDB yet, return that child, else nullptr.  */
+  lwp_info *pending_child (target_waitkind *kind) const
   {
     if (this->fork_relative == nullptr)
       return nullptr;
 
     gdb_assert (this->fork_relative->fork_relative == this);
 
-    /* In a fork parent/child relationship, the parent has a status pending and
-       the child does not, and a thread can only be in one such relationship
-       at most.  So we can recognize who is the parent based on which one has
-       a pending status.  */
+    /* In a parent/child relationship, the parent has a status pending
+       and the child does not, and a thread can only be in one such
+       relationship at most.  So we can recognize who is the parent
+       based on which one has a pending status.  */
     gdb_assert (!!this->status_pending_p
 		!= !!this->fork_relative->status_pending_p);
 
@@ -780,8 +782,10 @@ struct lwp_info
 
     const target_waitstatus &ws = this->waitstatus;
     gdb_assert (ws.kind () == TARGET_WAITKIND_FORKED
-		|| ws.kind () == TARGET_WAITKIND_VFORKED);
+		|| ws.kind () == TARGET_WAITKIND_VFORKED
+		|| ws.kind () == TARGET_WAITKIND_THREAD_CLONED);
 
+    *kind = ws.kind ();
     return this->fork_relative;
   }
 
diff --git a/gdbserver/server.cc b/gdbserver/server.cc
index fb7a1036320..3526e1d000e 100644
--- a/gdbserver/server.cc
+++ b/gdbserver/server.cc
@@ -1344,8 +1344,9 @@ handle_detach (char *own_buf)
 	continue;
 
       /* Only threads that have a pending fork event.  */
-      thread_info *child = target_thread_pending_child (thread);
-      if (child == nullptr)
+      target_waitkind kind;
+      thread_info *child = target_thread_pending_child (thread, &kind);
+      if (child == nullptr || kind == TARGET_WAITKIND_THREAD_CLONED)
 	continue;
 
       process_info *fork_child_process = get_thread_process (child);
@@ -1765,9 +1766,10 @@ handle_qxfer_threads_worker (thread_info *thread, struct buffer *buffer)
   gdb_byte *handle;
   bool handle_status = target_thread_handle (ptid, &handle, &handle_len);
 
-  /* If this is a fork or vfork child (has a fork parent), GDB does not yet
-     know about this process, and must not know about it until it gets the
-     corresponding (v)fork event.  Exclude this thread from the list.  */
+  /* If this is a (v)fork/clone child (has a (v)fork/clone parent),
+     GDB does not yet know about this thread, and must not know about
+     it until it gets the corresponding (v)fork/clone event.  Exclude
+     this thread from the list.  */
   if (target_thread_pending_parent (thread) != nullptr)
     return;
 
diff --git a/gdbserver/target.cc b/gdbserver/target.cc
index 70fec6d2078..ad32af0416e 100644
--- a/gdbserver/target.cc
+++ b/gdbserver/target.cc
@@ -808,7 +808,8 @@ process_stratum_target::thread_pending_parent (thread_info *thread)
 }
 
 thread_info *
-process_stratum_target::thread_pending_child (thread_info *thread)
+process_stratum_target::thread_pending_child (thread_info *thread,
+					      target_waitkind *kind)
 {
   return nullptr;
 }
diff --git a/gdbserver/target.h b/gdbserver/target.h
index 33142363a02..0aa7db49c18 100644
--- a/gdbserver/target.h
+++ b/gdbserver/target.h
@@ -479,13 +479,14 @@ public:
   virtual bool thread_handle (ptid_t ptid, gdb_byte **handle,
 			      int *handle_len);
 
-  /* If THREAD is a fork child that was not reported to GDB, return its parent
-     else nullptr.  */
+  /* If THREAD is a fork/vfork/clone child that was not reported to
+     GDB, return its parent else nullptr.  */
   virtual thread_info *thread_pending_parent (thread_info *thread);
 
-  /* If THREAD is the parent of a fork child that was not reported to GDB,
-     return this child, else nullptr.  */
-  virtual thread_info *thread_pending_child (thread_info *thread);
+  /* If THREAD is the parent of a fork/vfork/clone child that was not
+     reported to GDB, return this child, else nullptr.  */
+  virtual thread_info *thread_pending_child (thread_info *thread,
+					     target_waitkind *kind);
 
   /* Returns true if the target can software single step.  */
   virtual bool supports_software_single_step ();
@@ -701,9 +702,9 @@ target_thread_pending_parent (thread_info *thread)
 }
 
 static inline thread_info *
-target_thread_pending_child (thread_info *thread)
+target_thread_pending_child (thread_info *thread, target_waitkind *kind)
 {
-  return the_target->thread_pending_child (thread);
+  return the_target->thread_pending_child (thread, kind);
 }
 
 int read_inferior_memory (CORE_ADDR memaddr, unsigned char *myaddr, int len);