gdb/

2011-12-14  Pedro Alves  <pedro@codesourcery.com>

	PR threads/10729

	* linux-nat.c (linux_nat_new_thread): Change parameter to an lwp
	pointer.
	(linux_nat_prepare_to_resume): New global.
	(lwp_free): New.
	(purge_lwp_list): Use it.
	(add_lwp): Call linux_nat_new_thread even on the first LWP.
	Adjust to interface change.
	(delete_lwp): Call lwp_free instead of xfree.
	(detach_callback, linux_nat_detach, resume_lwp, linux_nat_resume)
	(linux_handle_syscall_trap, linux_handle_extended_wait)
	(linux_nat_filter_event, resume_stopped_resumed_lwps): Call
	linux_nat_prepare_to_resume before resuming.
	(linux_stop_lwp): New.
	(linux_nat_set_new_thread): Adjust.
	(linux_nat_set_prepare_to_resume): New.
	* linux-nat.h (struct arch_lwp_info): Forward declare.
	(struct lwp_info) <arch_private>: New field.
	(linux_stop_lwp): Declare.
	(linux_nat_set_new_thread): Adjust.
	(linux_nat_set_prepare_to_resume): New.

	* i386-nat.c (DR_NADDR, DR_STATUS, DR_CONTROL)
	(struct i386_debug_reg_state): Move to i386-nat.h.
	(dr_mirror): Comment.
	(i386_debug_reg_state): New.
	(i386_update_inferior_debug_regs): Simplify.
	(i386_stopped_data_address): Use the debug register state from the
	inferior, not from the local cache.
	* i386-nat.h (struct i386_dr_low_type): Delete reset_addr and
	unset_status fields.  New get_addr and get_control fields.
	(DR_FIRSTADDR, DR_LASTADDR, DR_CONTROL): Moved from i386-nat.c.
	(DR_NADDR, DR_STATUS): New.
	(struct i386_debug_reg_state): Moved from i386-nat.c.

	* amd64-linux-nat.c (struct arch_lwp_info): New.
	(amd64_linux_dr): Delete global.
	(amd64_linux_dr_get_addr): New.
	(amd64_linux_dr_get_control): New.
	(amd64_linux_dr_unset_status): Delete.
	(amd64_linux_dr_set_addr): Reimplement.
	(amd64_linux_dr_reset_addr): Delete.
	(update_debug_registers_callback): New.
	(amd64_linux_dr_set_control): Reimplement.
	(amd64_linux_dr_set_addr): Reimplement.
	(amd64_linux_prepare_to_resume): New.
	(amd64_linux_new_thread): Change parameter to an lwp pointer.
	Reimplement.
	(_initialize_amd64_linux_nat): No longer install
	i386_dr_low.reset_addr and i386_dr_low.unset_status.  Install
	amd64_linux_dr_get_control as i386_dr_low.get_control.  Install
	amd64_linux_dr_get_addr as i386_dr_low.get_addr.  Install
	amd64_linux_prepare_to_resume.
	* i386-linux-nat.c (DR_FIRSTADDR, DR_LASTADDR, DR_STATUS)
	(DR_CONTROL): Delete.
	(struct arch_lwp_info): New.
	(i386_linux_dr): Delete global.
	(i386_linux_dr_set_control): Reimplement.
	(i386_linux_dr_get_addr): New.
	(i386_linux_dr_set_addr): Reimplement.
	(i386_linux_dr_get_control): New.
	(update_debug_registers_callback): New.
	(i386_linux_dr_unset_status): Delete.
	(i386_linux_dr_set_addr): Reimplement.
	(i386_linux_prepare_to_resume): New.
	(i386_linux_new_thread): Change parameter to an lwp pointer.
	Reimplement.
	(_initialize_i386_linux_nat): No longer install
	i386_dr_low.reset_addr and i386_dr_low.unset_status.  Install
	i386_linux_dr_get_control as i386_dr_low.get_control.  Install
	i386_linux_dr_get_addr as i386_dr_low.get_addr.  Install
	i386_linux_prepare_to_resume.

	* arm-linux-nat.c (arm_linux_new_thread): Change parameter to an
	lwp pointer.  Adjust.
	* ia64-linux-nat.c (ia64_linux_new_thread): Likewise.
	* mips-linux-nat.c (mips_linux_new_thread): Likewise.
	* ppc-linux-nat.c (ppc_linux_new_thread): Likewise.
	* s390-nat.c (s390_fix_watch_points): Likewise.

	* i386-darwin-nat.c (DR_FIRSTADDR, DR_LASTADDR, DR_STATUS)
	(DR_CONTROL): Delete.
	(i386_darwin_dr_reset_addr): Delete.
	(i386_darwin_dr_get_addr): New.
	(i386_darwin_dr_get_control): New.
	* go32-nat.c
	(go32_get_dr7, go32_get_dr): New.
	(init_go32_ops): No longer install i386_dr_low.reset_addr.
	Install go32_get_dr7 as i386_dr_low.get_control.  Install
	go32_get_dr as i386_dr_low.get_addr.
	* i386bsd-nat.c (i386bsd_dr_get): New.
	(i386bsd_dr_reset_addr): Delete.
	(i386bsd_dr_get_addr): New.
	(i386bsd_dr_get_status): Use i386bsd_dr_get.
	(i386bsd_dr_get_control): New.
	* i386bsd-nat.h (i386bsd_dr_reset_addr): Delete.
	(i386bsd_dr_get_addr): New.
	(i386bsd_dr_get_control): New.
	* i386fbsd-nat.c (_initialize_i386fbsd_nat): No longer install
	i386_dr_low.reset_addr and i386_dr_low.unset_status.  Install
	i386bsd_dr_get_control as i386_dr_low.get_control.  Install
	i386bsd_dr_get_addr as i386_dr_low.get_addr.
	* windows-nat.c (init_windows_ops): No longer install
	i386_dr_low.reset_addr and i386_dr_low.unset_status.  Install
	cygwin_get_dr7 as i386_dr_low.get_control.  Install cygwin_get_dr
	as i386_dr_low.get_addr.
	(cygwin_get_dr): New.
	(cygwin_get_dr7): New.

gdb/testsuite/
2011-12-14  Pedro Alves  <pedro@codesourcery.com>

	PR threads/10729

	* gdb.mi/watch-nonstop.c: New file.
 	* gdb.mi/mi-watch-nonstop.exp: New file.

1 files changed, 60 insertions, 55 deletions

diff --git a/gdb/i386-nat.c b/gdb/i386-nat.c
index 568b79b..593401b 100644
--- a/gdb/i386-nat.c
+++ b/gdb/i386-nat.c
@@ -43,11 +43,6 @@ struct i386_dr_low_type i386_dr_low;
 /* Support for 8-byte wide hw watchpoints.  */
 #define TARGET_HAS_DR_LEN_8 (i386_dr_low.debug_register_length == 8)
 
-/* Debug registers' indices.  */
-#define DR_NADDR	4	/* The number of debug address registers.  */
-#define DR_STATUS	6	/* Index of debug status register (DR6).  */
-#define DR_CONTROL	7	/* Index of debug control register (DR7).  */
-
 /* DR7 Debug Control register fields.  */
 
 /* How many bits to skip in DR7 to get to R/W and LEN fields.  */
@@ -158,23 +153,6 @@ struct i386_dr_low_type i386_dr_low;
 /* A macro to loop over all debug registers.  */
 #define ALL_DEBUG_REGISTERS(i)	for (i = 0; i < DR_NADDR; i++)
 
-
-/* Global state needed to track h/w watchpoints.  */
-
-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.
-     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;
-
-  /* Reference counts for each debug register.  */
-  int dr_ref_count[DR_NADDR];
-};
-
 /* Clear the reference counts and forget everything we knew about the
    debug registers.  */
 
@@ -192,8 +170,16 @@ i386_init_dregs (struct i386_debug_reg_state *state)
   state->dr_status_mirror  = 0;
 }
 
+/* The local mirror of the inferior's debug registers.  Currently this
+   is a global, but it should really be per-inferior.  */
 static struct i386_debug_reg_state dr_mirror;
 
+struct i386_debug_reg_state *
+i386_debug_reg_state (void)
+{
+  return &dr_mirror;
+}
+
 /* Whether or not to print the mirrored debug registers.  */
 static int maint_show_dr;
 
@@ -513,22 +499,7 @@ i386_update_inferior_debug_regs (struct i386_debug_reg_state *new_state)
   ALL_DEBUG_REGISTERS (i)
     {
       if (I386_DR_VACANT (new_state, i) != I386_DR_VACANT (&dr_mirror, i))
-	{
-	  if (!I386_DR_VACANT (new_state, i))
-	    {
-	      i386_dr_low.set_addr (i, new_state->dr_mirror[i]);
-
-	      /* Only a sanity check for leftover bits (set possibly only
-		 by inferior).  */
-	      if (i386_dr_low.unset_status)
-		i386_dr_low.unset_status (I386_DR_WATCH_MASK (i));
-	    }
-	  else
-	    {
-	      if (i386_dr_low.reset_addr)
-		i386_dr_low.reset_addr (i);
-	    }
-	}
+	i386_dr_low.set_addr (i, new_state->dr_mirror[i]);
       else
 	gdb_assert (new_state->dr_mirror[i] == dr_mirror.dr_mirror[i]);
     }
@@ -634,28 +605,62 @@ i386_stopped_data_address (struct target_ops *ops, CORE_ADDR *addr_p)
   CORE_ADDR addr = 0;
   int i;
   int rc = 0;
+  /* The current thread's DR_STATUS.  We always need to read this to
+     check whether some watchpoint caused the trap.  */
   unsigned status;
-  unsigned control;
-  struct i386_debug_reg_state *state = &dr_mirror;
-
-  dr_mirror.dr_status_mirror = i386_dr_low.get_status ();
-  status = dr_mirror.dr_status_mirror;
-  control = dr_mirror.dr_control_mirror;
+  /* We need DR_CONTROL as well, but only iff DR_STATUS indicates a
+     data breakpoint trap.  Only fetch it when necessary, to avoid an
+     unnecessary extra syscall when no watchpoint triggered.  */
+  int control_p = 0;
+  unsigned control = 0;
+
+  /* In non-stop/async, threads can be running while we change the
+     global dr_mirror (and friends).  Say, we set a watchpoint, and
+     let threads resume.  Now, say you delete the watchpoint, or
+     add/remove watchpoints such that dr_mirror changes while threads
+     are running.  On targets that support non-stop,
+     inserting/deleting watchpoints updates the global dr_mirror only.
+     It does not update the real thread's debug registers; that's only
+     done prior to resume.  Instead, if threads are running when the
+     mirror changes, a temporary and transparent stop on all threads
+     is forced so they can get their copy of the debug registers
+     updated on re-resume.  Now, say, a thread hit a watchpoint before
+     having been updated with the new dr_mirror contents, and we
+     haven't yet handled the corresponding SIGTRAP.  If we trusted
+     dr_mirror below, we'd mistake the real trapped address (from the
+     last time we had updated debug registers in the thread) with
+     whatever was currently in dr_mirror.  So to fix this, dr_mirror
+     always represents intention, what we _want_ threads to have in
+     debug registers.  To get at the address and cause of the trap, we
+     need to read the state the thread still has in its debug
+     registers.
+
+     In sum, always get the current debug register values the current
+     thread has, instead of trusting the global mirror.  If the thread
+     was running when we last changed watchpoints, the mirror no
+     longer represents what was set in this thread's debug
+     registers.  */
+  status = i386_dr_low.get_status ();
 
   ALL_DEBUG_REGISTERS(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 (control, i) != 0
-	  /* This third condition makes sure DRi is not vacant, this
-	     avoids false positives in windows-nat.c.  */
-	  && !I386_DR_VACANT (state, i))
+      if (!I386_DR_WATCH_HIT (status, i))
+	continue;
+
+      if (!control_p)
+	{
+	  control = i386_dr_low.get_control ();
+	  control_p = 1;
+	}
+
+      /* 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.  */
+      if (I386_DR_GET_RW_LEN (control, i) != 0)
 	{
-	  addr = state->dr_mirror[i];
+	  addr = i386_dr_low.get_addr (i);
 	  rc = 1;
 	  if (maint_show_dr)
 	    i386_show_dr (&dr_mirror, "watchpoint_hit", addr, -1, hw_write);