Re: [PATCH 09/12] Make reinsert_breakpoint thread specific

[Yao Qi <qiyaoltc@gmail.com>]

Pedro Alves <palves@redhat.com> writes:

>> -	      uninsert_reinsert_breakpoints ();
>> +	      uninsert_reinsert_breakpoints (ptid_of_lwp (event_lwp));
>>  	      current_thread = saved_thread;
>
> Would it work to pass down the thread pointer directly?
>
> That would then allow pushing down the save current thread / restore
> current thread juggling to uninsert_reinsert_breakpoints too.

Yes, see the patch below,

-- 
Yao (齐尧)

From dd8c2dde049af0972d1da51506d990a97bf97193 Mon Sep 17 00:00:00 2001
From: Yao Qi <yao.qi@linaro.org>
Date: Thu, 19 May 2016 16:02:55 +0100
Subject: [PATCH] Make reinsert_breakpoint thread specific

V3: pass argument "thread" isntead of "ptid"

V2: rewrite commit log to make it easy to read,
    "id" -> "ptid",

This patch makes reinsert_breakpoint thread specific, which means we
insert and remove reinsert_breakpoint breakpoints for a specific
thread.  This motivation of this change is that I'll use
reinsert_breakpoint for vCont;s on software single step target, so that
GDBserver may insert one reinsert_breakpoint for one thread doing
step-over, and insert one reinsert_breakpoint for another thread doing
vCont;s.  After the operation of one thread is finished, GDBserver must
remove reinsert_breakpoint for that thread only.

On the other hand, reinsert_breakpoint is used for step-over nowadays.
GDBserver inserts reinsert_breakpoint, and wait only from the thread
doing step-over.  After the step-over is done, GDBserver removes the
reinsert_breakpoint.  If there is still any threads need step-over, do
the same again until all threads are finished step-over.  In other words,
reinsert_breakpoint is globally thread specific, but in an implicit way.
It is natural to make it explicitly thread specific.

gdb/gdbserver:

2016-06-14  Yao Qi  <yao.qi@linaro.org>

	* mem-break.c (struct reinsert_breakpoint) <ptid>: New field.
	(set_reinsert_breakpoint): New parameter ptid.  Callers updated.
	(clone_one_breakpoint): Likewise.
	(delete_reinsert_breakpoints): Change parameter to thread.
	Callers updated.
	(has_reinsert_breakpoints): Likewise.
	(uninsert_reinsert_breakpoints): Likewise.
	(reinsert_reinsert_breakpoints): Likewise.
	* mem-break.h (set_reinsert_breakpoint): Update declaration.
	(delete_reinsert_breakpoints): Likewise.
	(reinsert_reinsert_breakpoints): Likewise.
	(uninsert_reinsert_breakpoints): Likewise.
	(has_reinsert_breakpoints): Likewise.

diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index b0af178..60759c8 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -548,15 +548,11 @@ handle_extended_wait (struct lwp_info **orig_event_lwp, int wstat)
 	      && can_software_single_step ()
 	      && event == PTRACE_EVENT_VFORK)
 	    {
-	      struct thread_info *saved_thread = current_thread;
-
-	      current_thread = event_thr;
 	      /* If we leave reinsert breakpoints there, child will
 		 hit it, so uninsert reinsert breakpoints from parent
 		 (and child).  Once vfork child is done, reinsert
 		 them back to parent.  */
-	      uninsert_reinsert_breakpoints ();
-	      current_thread = saved_thread;
+	      uninsert_reinsert_breakpoints (event_thr);
 	    }
 
 	  clone_all_breakpoints (child_thr, event_thr);
@@ -591,17 +587,13 @@ handle_extended_wait (struct lwp_info **orig_event_lwp, int wstat)
 	  if (event_lwp->bp_reinsert != 0
 	      && can_software_single_step ())
 	    {
-	      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;
+	      delete_reinsert_breakpoints (child_thr);
 
-	      gdb_assert (has_reinsert_breakpoints (parent_proc));
-	      gdb_assert (!has_reinsert_breakpoints (child_proc));
+	      gdb_assert (has_reinsert_breakpoints (event_thr));
+	      gdb_assert (!has_reinsert_breakpoints (child_thr));
 	    }
 
 	  /* Report the event.  */
@@ -655,14 +647,9 @@ handle_extended_wait (struct lwp_info **orig_event_lwp, int wstat)
 
       if (event_lwp->bp_reinsert != 0 && can_software_single_step ())
 	{
-	  struct thread_info *saved_thread = current_thread;
-	  struct process_info *proc = get_thread_process (event_thr);
+	  reinsert_reinsert_breakpoints (event_thr);
 
-	  current_thread = event_thr;
-	  reinsert_reinsert_breakpoints ();
-	  current_thread = saved_thread;
-
-	  gdb_assert (has_reinsert_breakpoints (proc));
+	  gdb_assert (has_reinsert_breakpoints (event_thr));
 	}
 
       /* Report the event.  */
@@ -2559,11 +2546,9 @@ maybe_hw_step (struct thread_info *thread)
     return 1;
   else
     {
-      struct process_info *proc = get_thread_process (thread);
-
       /* GDBserver must insert reinsert breakpoint for software
 	 single step.  */
-      gdb_assert (has_reinsert_breakpoints (proc));
+      gdb_assert (has_reinsert_breakpoints (thread));
       return 0;
     }
 }
@@ -4153,7 +4138,7 @@ install_software_single_step_breakpoints (struct lwp_info *lwp)
   next_pcs = (*the_low_target.get_next_pcs) (regcache);
 
   for (i = 0; VEC_iterate (CORE_ADDR, next_pcs, i, pc); ++i)
-    set_reinsert_breakpoint (pc);
+    set_reinsert_breakpoint (pc, current_ptid);
 
   do_cleanups (old_chain);
 }
@@ -4296,7 +4281,7 @@ linux_resume_one_lwp_throw (struct lwp_info *lwp,
     {
       /* If the thread isn't doing step-over, there shouldn't be any
 	 reinsert breakpoints.  */
-      gdb_assert (!has_reinsert_breakpoints (proc));
+      gdb_assert (!has_reinsert_breakpoints (thread));
     }
 
   if (fast_tp_collecting == 1)
@@ -4789,8 +4774,8 @@ finish_step_over (struct lwp_info *lwp)
 	 threads but LWP stopped while doing that.  */
       if (!can_hardware_single_step ())
 	{
-	  gdb_assert (has_reinsert_breakpoints (current_process ()));
-	  delete_reinsert_breakpoints ();
+	  gdb_assert (has_reinsert_breakpoints (current_thread));
+	  delete_reinsert_breakpoints (current_thread);
 	}
 
       step_over_bkpt = null_ptid;
diff --git a/gdb/gdbserver/mem-break.c b/gdb/gdbserver/mem-break.c
index c14219e..65ca3f9 100644
--- a/gdb/gdbserver/mem-break.c
+++ b/gdb/gdbserver/mem-break.c
@@ -211,6 +211,9 @@ struct other_breakpoint
 struct reinsert_breakpoint
 {
   struct breakpoint base;
+
+  /* Thread the reinsert breakpoint belongs to.  */
+  ptid_t ptid;
 };
 
 /* Return the breakpoint size from its kind.  */
@@ -1476,17 +1479,21 @@ gdb_breakpoint_here (CORE_ADDR where)
 }
 
 void
-set_reinsert_breakpoint (CORE_ADDR stop_at)
+set_reinsert_breakpoint (CORE_ADDR stop_at, ptid_t ptid)
 {
-  struct breakpoint *bp;
+  struct reinsert_breakpoint *bp;
+
+  gdb_assert (ptid_get_pid (current_ptid) == ptid_get_pid (ptid));
 
-  bp = set_breakpoint_type_at (reinsert_breakpoint, stop_at, NULL);
+  bp = (struct reinsert_breakpoint *) set_breakpoint_type_at (reinsert_breakpoint,
+							      stop_at, NULL);
+  bp->ptid = ptid;
 }
 
 void
-delete_reinsert_breakpoints (void)
+delete_reinsert_breakpoints (struct thread_info *thread)
 {
-  struct process_info *proc = current_process ();
+  struct process_info *proc = get_thread_process (thread);
   struct breakpoint *bp, **bp_link;
 
   bp = proc->breakpoints;
@@ -1494,11 +1501,17 @@ delete_reinsert_breakpoints (void)
 
   while (bp)
     {
-      if (bp->type == reinsert_breakpoint)
+      if (bp->type == reinsert_breakpoint
+	  && ptid_equal (((struct reinsert_breakpoint *) bp)->ptid,
+			 ptid_of (thread)))
 	{
+	  struct thread_info *saved_thread = current_thread;
+
+	  current_thread = thread;
 	  *bp_link = bp->next;
 	  release_breakpoint (proc, bp);
 	  bp = *bp_link;
+	  current_thread = saved_thread;
 	}
       else
 	{
@@ -1578,21 +1591,29 @@ uninsert_all_breakpoints (void)
 }
 
 void
-uninsert_reinsert_breakpoints (void)
+uninsert_reinsert_breakpoints (struct thread_info *thread)
 {
-  struct process_info *proc = current_process ();
+  struct process_info *proc = get_thread_process (thread);
   struct breakpoint *bp;
 
   for (bp = proc->breakpoints; bp != NULL; bp = bp->next)
     {
-    if (bp->type == reinsert_breakpoint)
+    if (bp->type == reinsert_breakpoint
+	&& ptid_equal (((struct reinsert_breakpoint *) bp)->ptid,
+		       ptid_of (thread)))
       {
 	gdb_assert (bp->raw->inserted > 0);
 
 	/* Only uninsert the raw breakpoint if it only belongs to a
 	   reinsert breakpoint.  */
 	if (bp->raw->refcount == 1)
-	  uninsert_raw_breakpoint (bp->raw);
+	  {
+	    struct thread_info *saved_thread = current_thread;
+
+	    current_thread = thread;
+	    uninsert_raw_breakpoint (bp->raw);
+	    current_thread = saved_thread;
+	  }
       }
     }
 }
@@ -1642,8 +1663,9 @@ reinsert_breakpoints_at (CORE_ADDR pc)
 }
 
 int
-has_reinsert_breakpoints (struct process_info *proc)
+has_reinsert_breakpoints (struct thread_info *thread)
 {
+  struct process_info *proc = get_thread_process (thread);
   struct breakpoint *bp, **bp_link;
 
   bp = proc->breakpoints;
@@ -1651,7 +1673,9 @@ has_reinsert_breakpoints (struct process_info *proc)
 
   while (bp)
     {
-      if (bp->type == reinsert_breakpoint)
+      if (bp->type == reinsert_breakpoint
+	  && ptid_equal (((struct reinsert_breakpoint *) bp)->ptid,
+			 ptid_of (thread)))
 	return 1;
       else
 	{
@@ -1677,19 +1701,27 @@ reinsert_all_breakpoints (void)
 }
 
 void
-reinsert_reinsert_breakpoints (void)
+reinsert_reinsert_breakpoints (struct thread_info *thread)
 {
-  struct process_info *proc = current_process ();
+  struct process_info *proc = get_thread_process (thread);
   struct breakpoint *bp;
 
   for (bp = proc->breakpoints; bp != NULL; bp = bp->next)
     {
-      if (bp->type == reinsert_breakpoint)
+      if (bp->type == reinsert_breakpoint
+	  && ptid_equal (((struct reinsert_breakpoint *) bp)->ptid,
+			 ptid_of (thread)))
 	{
 	  gdb_assert (bp->raw->inserted > 0);
 
 	  if (bp->raw->refcount == 1)
-	    reinsert_raw_breakpoint (bp->raw);
+	    {
+	      struct thread_info *saved_thread = current_thread;
+
+	      current_thread = thread;
+	      reinsert_raw_breakpoint (bp->raw);
+	      current_thread = saved_thread;
+	    }
 	}
     }
 }
@@ -2113,7 +2145,7 @@ clone_agent_expr (const struct agent_expr *src_ax)
 /* Deep-copy the contents of one breakpoint to another.  */
 
 static struct breakpoint *
-clone_one_breakpoint (const struct breakpoint *src)
+clone_one_breakpoint (const struct breakpoint *src, ptid_t ptid)
 {
   struct breakpoint *dest;
   struct raw_breakpoint *dest_raw;
@@ -2174,6 +2206,9 @@ clone_one_breakpoint (const struct breakpoint *src)
 	= XCNEW (struct reinsert_breakpoint);
 
       dest = (struct breakpoint *) reinsert_dest;
+      /* Since reinsert breakpoint is thread specific, don't copy
+	 thread id from SRC, use ID instead.  */
+      reinsert_dest->ptid = ptid;
     }
   else
     gdb_assert_not_reached ("unhandled breakpoint type");
@@ -2201,7 +2236,7 @@ clone_all_breakpoints (struct thread_info *child_thread,
 
   for (bp = parent_proc->breakpoints; bp != NULL; bp = bp->next)
     {
-      new_bkpt = clone_one_breakpoint (bp);
+      new_bkpt = clone_one_breakpoint (bp, ptid_of (child_thread));
       APPEND_TO_LIST (new_list, new_bkpt, bkpt_tail);
       APPEND_TO_LIST (new_raw_list, new_bkpt->raw, raw_bkpt_tail);
     }
diff --git a/gdb/gdbserver/mem-break.h b/gdb/gdbserver/mem-break.h
index d633003..3322ec5 100644
--- a/gdb/gdbserver/mem-break.h
+++ b/gdb/gdbserver/mem-break.h
@@ -152,31 +152,32 @@ struct breakpoint *set_breakpoint_at (CORE_ADDR where,
 
 int delete_breakpoint (struct breakpoint *bkpt);
 
-/* Set a reinsert breakpoint at STOP_AT.  */
+/* Set a reinsert breakpoint at STOP_AT for thread represented by
+   PTID.  */
 
-void set_reinsert_breakpoint (CORE_ADDR stop_at);
+void set_reinsert_breakpoint (CORE_ADDR stop_at, ptid_t ptid);
 
-/* Delete all reinsert breakpoints.  */
+/* Delete all reinsert breakpoints of THREAD.  */
 
-void delete_reinsert_breakpoints (void);
+void delete_reinsert_breakpoints (struct thread_info *thread);
 
-/* Reinsert all reinsert breakpoints of the current process.  */
+/* Reinsert all reinsert breakpoints of THREAD.  */
 
-void reinsert_reinsert_breakpoints (void);
+void reinsert_reinsert_breakpoints (struct thread_info *thread);
 
-/* Uninsert all reinsert breakpoints of the current process.  This
-   still leaves the reinsert breakpoints in the table.  */
+/* Uninsert all reinsert breakpoints of THREAD.  This still leaves
+   the reinsert breakpoints in the table.  */
 
-void uninsert_reinsert_breakpoints (void);
+void uninsert_reinsert_breakpoints (struct thread_info *thread);
 
 /* Reinsert breakpoints at WHERE (and change their status to
    inserted).  */
 
 void reinsert_breakpoints_at (CORE_ADDR where);
 
-/* Process PROC has reinsert breakpoints or not.  */
+/* The THREAD has reinsert breakpoints or not.  */
 
-int has_reinsert_breakpoints (struct process_info *proc);
+int has_reinsert_breakpoints (struct thread_info *thread);
 
 /* Uninsert breakpoints at WHERE (and change their status to
    uninserted).  This still leaves the breakpoints in the table.  */