PR threads/10729

	* linux-x86-low.c (update_debug_registers_callback): New.
	(i386_dr_low_set_addr): Use it.
	(i386_dr_low_get_addr): New.
	(i386_dr_low_set_control): Use update_debug_registers_callback.
	(i386_dr_low_get_control): New.
	(i386_dr_low_get_status): Adjust.
	* linux-low.c (linux_stop_lwp): New.
	* linux-low.h (linux_stop_lwp): Declare.

	* i386-low.c (I386_DR_GET_RW_LEN): Take the dr7 contents as
	argument instead of a i386_debug_reg_state.
	(I386_DR_WATCH_HIT): Take the dr6 contents as argument instead of
	a i386_debug_reg_state.
	(i386_insert_aligned_watchpoint): Adjust.
	(i386_remove_aligned_watchpoint): Adjust.
	(i386_low_stopped_data_address): Read the debug registers from the
	inferior instead of from the mirrors.
	* i386-low.h (struct i386_debug_reg_state): Extend comment.
	(i386_dr_low_get_addr): Declare.
	(i386_dr_low_get_control): Declare.
	(i386_dr_low_get_status): Change prototype.

	* win32-i386-low.c (dr_status_mirror, dr_control_mirror): New globals.
	(i386_dr_low_get_addr): New.
	(i386_dr_low_get_control): New.
	(i386_dr_low_get_status): Adjust prototype.  Return
	dr_status_mirror.
	(i386_initial_stuff): Clear dr_status_mirror and
	dr_control_mirror.
	(i386_get_thread_context): Adjust.
	(i386_set_thread_context): Adjust.
	(i386_thread_added): Adjust.

7 files changed, 150 insertions, 47 deletions

diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index 3ad62ba..6e6127e 100644
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,3 +1,40 @@
+2010-08-25  Pedro Alves  <pedro@codesourcery.com>
+
+	PR threads/10729
+
+	* linux-x86-low.c (update_debug_registers_callback): New.
+	(i386_dr_low_set_addr): Use it.
+	(i386_dr_low_get_addr): New.
+	(i386_dr_low_set_control): Use update_debug_registers_callback.
+	(i386_dr_low_get_control): New.
+	(i386_dr_low_get_status): Adjust.
+	* linux-low.c (linux_stop_lwp): New.
+	* linux-low.h (linux_stop_lwp): Declare.
+
+	* i386-low.c (I386_DR_GET_RW_LEN): Take the dr7 contents as
+	argument instead of a i386_debug_reg_state.
+	(I386_DR_WATCH_HIT): Take the dr6 contents as argument instead of
+	a i386_debug_reg_state.
+	(i386_insert_aligned_watchpoint): Adjust.
+	(i386_remove_aligned_watchpoint): Adjust.
+	(i386_low_stopped_data_address): Read the debug registers from the
+	inferior instead of from the mirrors.
+	* i386-low.h (struct i386_debug_reg_state): Extend comment.
+	(i386_dr_low_get_addr): Declare.
+	(i386_dr_low_get_control): Declare.
+	(i386_dr_low_get_status): Change prototype.
+
+	* win32-i386-low.c (dr_status_mirror, dr_control_mirror): New globals.
+	(i386_dr_low_get_addr): New.
+	(i386_dr_low_get_control): New.
+	(i386_dr_low_get_status): Adjust prototype.  Return
+	dr_status_mirror.
+	(i386_initial_stuff): Clear dr_status_mirror and
+	dr_control_mirror.
+	(i386_get_thread_context): Adjust.
+	(i386_set_thread_context): Adjust.
+	(i386_thread_added): Adjust.
+
 2010-08-24  Pedro Alves  <pedro@codesourcery.com>
 
 	* linux-low.h (linux_thread_area): Delete declaration.
diff --git a/gdb/gdbserver/i386-low.c b/gdb/gdbserver/i386-low.c
index 494b808..f13ae26 100644
--- a/gdb/gdbserver/i386-low.c
+++ b/gdb/gdbserver/i386-low.c
@@ -132,12 +132,12 @@ enum target_hw_bp_type
   } while (0)
 
 /* Get from DR7 the RW and LEN fields for the I'th debug register.  */
-#define I386_DR_GET_RW_LEN(state, i) \
-  (((state)->dr_control_mirror \
+#define I386_DR_GET_RW_LEN(dr7, i) \
+  (((dr7) \
     >> (DR_CONTROL_SHIFT + DR_CONTROL_SIZE * (i))) & 0x0f)
 
 /* Did the watchpoint whose address is in the I'th register break?  */
-#define I386_DR_WATCH_HIT(state,i) ((state)->dr_status_mirror & (1 << (i)))
+#define I386_DR_WATCH_HIT(dr6, i) ((dr6) & (1 << (i)))
 
 /* A macro to loop over all debug registers.  */
 #define ALL_DEBUG_REGISTERS(i)	for (i = 0; i < DR_NADDR; i++)
@@ -271,7 +271,7 @@ i386_insert_aligned_watchpoint (struct i386_debug_reg_state *state,
     {
       if (!I386_DR_VACANT (state, i)
 	  && state->dr_mirror[i] == addr
-	  && I386_DR_GET_RW_LEN (state, i) == len_rw_bits)
+	  && I386_DR_GET_RW_LEN (state->dr_control_mirror, i) == len_rw_bits)
 	{
 	  state->dr_ref_count[i]++;
 	  return 0;
@@ -329,7 +329,7 @@ i386_remove_aligned_watchpoint (struct i386_debug_reg_state *state,
     {
       if (!I386_DR_VACANT (state, i)
 	  && state->dr_mirror[i] == addr
-	  && I386_DR_GET_RW_LEN (state, i) == len_rw_bits)
+	  && I386_DR_GET_RW_LEN (state->dr_control_mirror, i) == len_rw_bits)
 	{
 	  if (--state->dr_ref_count[i] == 0) /* No longer in use?  */
 	    {
@@ -539,21 +539,26 @@ i386_low_stopped_data_address (struct i386_debug_reg_state *state,
   CORE_ADDR addr = 0;
   int i;
   int rc = 0;
+  unsigned status;
+  unsigned control;
 
-  /* Get dr_status_mirror for use by I386_DR_WATCH_HIT.  */
-  i386_dr_low_get_status (state);
+  /* Get the current values the inferior has.  If the thread was
+     running when we last changed watchpoints, the mirror no longer
+     represents what was set in this LWP's debug registers.  */
+  status = i386_dr_low_get_status ();
+  control = i386_dr_low_get_control ();
 
   ALL_DEBUG_REGISTERS (i)
     {
-      if (I386_DR_WATCH_HIT (state, i)
+      if (I386_DR_WATCH_HIT (status, i)
 	  /* This second condition makes sure DRi is set up for a data
 	     watchpoint, not a hardware breakpoint.  The reason is
 	     that GDB doesn't call the target_stopped_data_address
 	     method except for data watchpoints.  In other words, I'm
 	     being paranoiac.  */
-	  && I386_DR_GET_RW_LEN (state, i) != 0)
+	  && I386_DR_GET_RW_LEN (control, i) != 0)
 	{
-	  addr = state->dr_mirror[i];
+	  addr = i386_dr_low_get_addr (i);
 	  rc = 1;
 	  if (debug_hw_points)
 	    i386_show_dr (state, "watchpoint_hit", addr, -1, hw_write);
diff --git a/gdb/gdbserver/i386-low.h b/gdb/gdbserver/i386-low.h
index 7f7f76b..2566b7b 100644
--- a/gdb/gdbserver/i386-low.h
+++ b/gdb/gdbserver/i386-low.h
@@ -42,7 +42,10 @@
 struct i386_debug_reg_state
 {
   /* Mirror the inferior's DRi registers.  We keep the status and
-     control registers separated because they don't hold addresses.  */
+     control registers separated because they don't hold addresses.
+     Note that since we can change these mirrors while threads are
+     running, we never trust them to explain a cause of a trap.
+     For that, we need to peek directly in the inferior registers.  */
   CORE_ADDR dr_mirror[DR_NADDR];
   unsigned dr_status_mirror, dr_control_mirror;
 
@@ -100,9 +103,14 @@ extern int i386_low_stopped_by_watchpoint (struct i386_debug_reg_state *state);
 extern void i386_dr_low_set_addr (const struct i386_debug_reg_state *state,
 				  int regnum);
 
+/* Return the inferior's debug register REGNUM.  */
+extern CORE_ADDR i386_dr_low_get_addr (int regnum);
+
 /* Update the inferior's DR7 debug control register from STATE.  */
 extern void i386_dr_low_set_control (const struct i386_debug_reg_state *state);
 
-/* Get the value of the inferior's DR6 debug status register
-   and record it in STATE.  */
-extern void i386_dr_low_get_status (struct i386_debug_reg_state *state);
+/* Return the value of the inferior's DR7 debug control register.  */
+extern unsigned i386_dr_low_get_control (void);
+
+/* Return the value of the inferior's DR6 debug status register.  */
+extern unsigned i386_dr_low_get_status (void);
diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index a162385..22d8eb1 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -2478,6 +2478,12 @@ kill_lwp (unsigned long lwpid, int signo)
   return kill (lwpid, signo);
 }
 
+void
+linux_stop_lwp (struct lwp_info *lwp)
+{
+  send_sigstop (lwp);
+}
+
 static void
 send_sigstop (struct lwp_info *lwp)
 {
diff --git a/gdb/gdbserver/linux-low.h b/gdb/gdbserver/linux-low.h
index c5ca1d7..5b584d0 100644
--- a/gdb/gdbserver/linux-low.h
+++ b/gdb/gdbserver/linux-low.h
@@ -259,6 +259,7 @@ int elf_64_file_p (const char *file);
 
 void linux_attach_lwp (unsigned long pid);
 struct lwp_info *find_lwp_pid (ptid_t ptid);
+void linux_stop_lwp (struct lwp_info *lwp);
 
 /* From thread-db.c  */
 int thread_db_init (int use_events);
diff --git a/gdb/gdbserver/linux-x86-low.c b/gdb/gdbserver/linux-x86-low.c
index 1e0d684..841f053 100644
--- a/gdb/gdbserver/linux-x86-low.c
+++ b/gdb/gdbserver/linux-x86-low.c
@@ -461,30 +461,55 @@ x86_linux_dr_set (ptid_t ptid, int regnum, unsigned long value)
     error ("Couldn't write debug register");
 }
 
+static int
+update_debug_registers_callback (struct inferior_list_entry *entry,
+				 void *pid_p)
+{
+  struct lwp_info *lwp = (struct lwp_info *) entry;
+  int pid = *(int *) pid_p;
+
+  /* Only update the threads of this process.  */
+  if (pid_of (lwp) == pid)
+    {
+      /* The actual update is done later just before resuming the lwp,
+	 we just mark that the registers need updating.  */
+      lwp->arch_private->debug_registers_changed = 1;
+
+      /* If the lwp isn't stopped, force it to momentarily pause, so
+	 we can update its debug registers.  */
+      if (!lwp->stopped)
+	linux_stop_lwp (lwp);
+    }
+
+  return 0;
+}
+
 /* Update the inferior's debug register REGNUM from STATE.  */
 
 void
 i386_dr_low_set_addr (const struct i386_debug_reg_state *state, int regnum)
 {
-  struct inferior_list_entry *lp;
-  CORE_ADDR addr;
-  /* Only need to update the threads of this process.  */
+  /* Only update the threads of this process.  */
   int pid = pid_of (get_thread_lwp (current_inferior));
 
   if (! (regnum >= 0 && regnum <= DR_LASTADDR - DR_FIRSTADDR))
     fatal ("Invalid debug register %d", regnum);
 
-  addr = state->dr_mirror[regnum];
+  find_inferior (&all_lwps, update_debug_registers_callback, &pid);
+}
 
-  for (lp = all_lwps.head; lp; lp = lp->next)
-    {
-      struct lwp_info *lwp = (struct lwp_info *) lp;
+/* Return the inferior's debug register REGNUM.  */
 
-      /* The actual update is done later, we just mark that the register
-	 needs updating.  */
-      if (pid_of (lwp) == pid)
-	lwp->arch_private->debug_registers_changed = 1;
-    }
+CORE_ADDR
+i386_dr_low_get_addr (int regnum)
+{
+  struct lwp_info *lwp = get_thread_lwp (current_inferior);
+  ptid_t ptid = ptid_of (lwp);
+
+  /* DR6 and DR7 are retrieved with some other way.  */
+  gdb_assert (DR_FIRSTADDR <= regnum && regnum < DR_LASTADDR);
+
+  return x86_linux_dr_get (ptid, regnum);
 }
 
 /* Update the inferior's DR7 debug control register from STATE.  */
@@ -492,31 +517,33 @@ i386_dr_low_set_addr (const struct i386_debug_reg_state *state, int regnum)
 void
 i386_dr_low_set_control (const struct i386_debug_reg_state *state)
 {
-  struct inferior_list_entry *lp;
-  /* Only need to update the threads of this process.  */
+  /* Only update the threads of this process.  */
   int pid = pid_of (get_thread_lwp (current_inferior));
 
-  for (lp = all_lwps.head; lp; lp = lp->next)
-    {
-      struct lwp_info *lwp = (struct lwp_info *) lp;
+  find_inferior (&all_lwps, update_debug_registers_callback, &pid);
+}
 
-      /* The actual update is done later, we just mark that the register
-	 needs updating.  */
-      if (pid_of (lwp) == pid)
-	lwp->arch_private->debug_registers_changed = 1;
-    }
+/* Return the inferior's DR7 debug control register.  */
+
+unsigned
+i386_dr_low_get_control (void)
+{
+  struct lwp_info *lwp = get_thread_lwp (current_inferior);
+  ptid_t ptid = ptid_of (lwp);
+
+  return x86_linux_dr_get (ptid, DR_CONTROL);
 }
 
 /* Get the value of the DR6 debug status register from the inferior
    and record it in STATE.  */
 
-void
-i386_dr_low_get_status (struct i386_debug_reg_state *state)
+unsigned
+i386_dr_low_get_status (void)
 {
   struct lwp_info *lwp = get_thread_lwp (current_inferior);
   ptid_t ptid = ptid_of (lwp);
 
-  state->dr_status_mirror = x86_linux_dr_get (ptid, DR_STATUS);
+  return x86_linux_dr_get (ptid, DR_STATUS);
 }
 
 /* Watchpoint support.  */
diff --git a/gdb/gdbserver/win32-i386-low.c b/gdb/gdbserver/win32-i386-low.c
index 2e67615..2d77211 100644
--- a/gdb/gdbserver/win32-i386-low.c
+++ b/gdb/gdbserver/win32-i386-low.c
@@ -37,6 +37,8 @@ void init_registers_i386 (void);
 #endif
 
 static struct i386_debug_reg_state debug_reg_state;
+static unsigned dr_status_mirror;
+static unsigned dr_control_mirror;
 
 static int debug_registers_changed = 0;
 static int debug_registers_used = 0;
@@ -56,6 +58,14 @@ i386_dr_low_set_addr (const struct i386_debug_reg_state *state, int regnum)
   debug_registers_used = 1;
 }
 
+CORE_ADDR
+i386_dr_low_get_addr (int regnum)
+{
+  gdb_assert (DR_FIRSTADDR <= regnum && regnum < DR_LASTADDR);
+
+  return debug_reg_state.dr_mirror[regnum];
+}
+
 /* Update the inferior's DR7 debug control register from STATE.  */
 
 void
@@ -68,14 +78,21 @@ i386_dr_low_set_control (const struct i386_debug_reg_state *state)
   debug_registers_used = 1;
 }
 
+unsigned
+i386_dr_low_get_control (void)
+{
+  return dr_control_mirror;
+}
+
 /* Get the value of the DR6 debug status register from the inferior
    and record it in STATE.  */
 
-void
-i386_dr_low_get_status (struct i386_debug_reg_state *state)
+unsigned
+i386_dr_low_get_status (void)
 {
   /* We don't need to do anything here, the last call to thread_rec for
      current_event.dwThreadId id has already set it.  */
+  return dr_status_mirror;
 }
 
 /* Watchpoint support.  */
@@ -133,6 +150,8 @@ i386_initial_stuff (void)
   i386_low_init_dregs (&debug_reg_state);
   debug_registers_changed = 0;
   debug_registers_used = 0;
+  dr_status_mirror = 0;
+  dr_control_mirror = 0;
 }
 
 static void
@@ -171,8 +190,8 @@ i386_get_thread_context (win32_thread_info *th, DEBUG_EVENT* current_event)
       dr->dr_mirror[1] = th->context.Dr1;
       dr->dr_mirror[2] = th->context.Dr2;
       dr->dr_mirror[3] = th->context.Dr3;
-      dr->dr_status_mirror = th->context.Dr6;
-      dr->dr_control_mirror = th->context.Dr7;
+      dr_status_mirror = th->context.Dr6;
+      dr_control_mirror = th->context.Dr7;
     }
 }
 
@@ -186,9 +205,9 @@ i386_set_thread_context (win32_thread_info *th, DEBUG_EVENT* current_event)
       th->context.Dr1 = dr->dr_mirror[1];
       th->context.Dr2 = dr->dr_mirror[2];
       th->context.Dr3 = dr->dr_mirror[3];
-      /* th->context.Dr6 = dr->dr_status_mirror;
+      /* th->context.Dr6 = dr_status_mirror;
 	 FIXME: should we set dr6 also ?? */
-      th->context.Dr7 = dr->dr_control_mirror;
+      th->context.Dr7 = dr_control_mirror;
     }
 
   SetThreadContext (th->h, &th->context);
@@ -208,9 +227,9 @@ i386_thread_added (win32_thread_info *th)
       th->context.Dr1 = dr->dr_mirror[1];
       th->context.Dr2 = dr->dr_mirror[2];
       th->context.Dr3 = dr->dr_mirror[3];
-      /* th->context.Dr6 = dr->dr_status_mirror;
+      /* th->context.Dr6 = dr_status_mirror;
 	 FIXME: should we set dr6 also ?? */
-      th->context.Dr7 = dr->dr_control_mirror;
+      th->context.Dr7 = dr_control_mirror;
 
       SetThreadContext (th->h, &th->context);
       th->context.ContextFlags = 0;