[binutils-gdb] Windows gdb+gdbserver: Eliminate thread_rec(INVALIDATE_CONTEXT) calls

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=0ab4174c4ccc745a125102eeed7c47e77b6fe438

commit 0ab4174c4ccc745a125102eeed7c47e77b6fe438
Author: Pedro Alves <[email protected]>
Date:   Mon May 8 21:36:28 2023 +0100

    Windows gdb+gdbserver: Eliminate thread_rec(INVALIDATE_CONTEXT) calls
    
    Replace thread_rec(INVALIDATE_CONTEXT) calls with find_thread, and
    invalidate_context / suspend calls in the spots that might need those.
    
    I don't know why does the INVALIDATE_CONTEXT implementation in GDB
    avoid suspending the event thread:
    
            case INVALIDATE_CONTEXT:
              if (ptid.lwp () != current_event.dwThreadId)
                th->suspend ();
    
    Checks for a global "current_event" get in the way of non-stop support
    later in the series, as each thread will have its own "last debug
    event".  Regardless, it should be fine to suspend the event thread.
    As a data point, the GDBserver implementation always suspends.  So
    this patch does not try to avoid suspending the event thread on the
    native side either.
    
    Approved-By: Tom Tromey <[email protected]>
    Change-Id: I8d2f0a749d23329956e62362a7007189902dddb5

Diff:
---
 gdb/aarch64-windows-nat.c |  2 ++
 gdb/nat/windows-nat.h     |  2 --
 gdb/windows-nat.c         | 21 +++++++--------------
 gdb/x86-windows-nat.c     |  2 ++
 gdbserver/win32-low.cc    | 10 ++++------
 5 files changed, 15 insertions(+), 22 deletions(-)

diff --git a/gdb/aarch64-windows-nat.c b/gdb/aarch64-windows-nat.c
index c375bbf2ddd..d43ee6f13fe 100644
--- a/gdb/aarch64-windows-nat.c
+++ b/gdb/aarch64-windows-nat.c
@@ -185,6 +185,7 @@ aarch64_windows_nat_target::fill_thread_context (windows_thread_info *th)
 
   if (context->ContextFlags == 0)
     {
+      th->suspend ();
       context->ContextFlags = WindowsContext<decltype(context)>::all;
       CHECK (get_thread_context (th->h, context));
     }
@@ -285,6 +286,7 @@ aarch64_windows_nat_target::store_one_register (const struct regcache *regcache,
 						windows_thread_info *th, int r)
 {
   gdb_assert (r >= 0);
+  gdb_assert (th->context.ContextFlags != 0);
 
   char *context_ptr = (char *) &th->context;
 
diff --git a/gdb/nat/windows-nat.h b/gdb/nat/windows-nat.h
index 24ef6cc3f9c..1a564fbf11b 100644
--- a/gdb/nat/windows-nat.h
+++ b/gdb/nat/windows-nat.h
@@ -109,8 +109,6 @@ enum thread_disposition_type
 {
   /* Invalidate the context, but do not suspend the thread.  */
   DONT_SUSPEND,
-  /* Invalidate the context and suspend the thread.  */
-  INVALIDATE_CONTEXT
 };
 
 /* A single pending stop.  See "pending_stops" for more
diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index e8df5e053e6..ca9a197d64e 100644
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -284,11 +284,6 @@ windows_per_inferior::thread_rec (ptid_t ptid,
     {
       switch (disposition)
 	{
-	case INVALIDATE_CONTEXT:
-	  if (ptid.lwp () != current_event.dwThreadId)
-	    th->suspend ();
-	  invalidate_thread_context (th);
-	  break;
 	case DONT_SUSPEND:
 	  th->suspended = -1;
 	  invalidate_thread_context (th);
@@ -392,8 +387,7 @@ windows_nat_target::delete_thread (ptid_t ptid, DWORD exit_code,
 void
 windows_nat_target::fetch_registers (struct regcache *regcache, int r)
 {
-  windows_thread_info *th
-    = windows_process->thread_rec (regcache->ptid (), INVALIDATE_CONTEXT);
+  windows_thread_info *th = windows_process->find_thread (regcache->ptid ());
 
   /* Check if TH exists.  Windows sometimes uses a non-existent
      thread id in its events.  */
@@ -415,8 +409,7 @@ windows_nat_target::fetch_registers (struct regcache *regcache, int r)
 void
 windows_nat_target::store_registers (struct regcache *regcache, int r)
 {
-  windows_thread_info *th
-    = windows_process->thread_rec (regcache->ptid (), INVALIDATE_CONTEXT);
+  windows_thread_info *th = windows_process->find_thread (regcache->ptid ());
 
   /* Check if TH exists.  Windows sometimes uses a non-existent
      thread id in its events.  */
@@ -933,7 +926,9 @@ windows_nat_target::get_windows_debug_event
       *ourstatus = stop->status;
 
       ptid_t ptid (windows_process->current_event.dwProcessId, thread_id);
-      windows_process->thread_rec (ptid, INVALIDATE_CONTEXT);
+      windows_thread_info *th = windows_process->find_thread (ptid);
+      if (th != nullptr)
+	windows_process->invalidate_thread_context (th);
       return ptid;
     }
 
@@ -1151,8 +1146,7 @@ windows_nat_target::get_windows_debug_event
 	  && windows_process->windows_initialization_done)
 	{
 	  ptid_t ptid = ptid_t (current_event->dwProcessId, thread_id, 0);
-	  windows_thread_info *th
-	    = windows_process->thread_rec (ptid, INVALIDATE_CONTEXT);
+	  windows_thread_info *th = windows_process->find_thread (ptid);
 	  th->stopped_at_software_breakpoint = true;
 	  th->pc_adjusted = false;
 	}
@@ -1190,8 +1184,7 @@ windows_nat_target::wait (ptid_t ptid, struct target_waitstatus *ourstatus,
 	  if (ourstatus->kind () != TARGET_WAITKIND_EXITED
 	      && ourstatus->kind () !=  TARGET_WAITKIND_SIGNALLED)
 	    {
-	      windows_thread_info *th
-		= windows_process->thread_rec (result, INVALIDATE_CONTEXT);
+	      windows_thread_info *th = windows_process->find_thread (result);
 
 	      if (th != nullptr)
 		{
diff --git a/gdb/x86-windows-nat.c b/gdb/x86-windows-nat.c
index d76b89b186a..5b0f7066fba 100644
--- a/gdb/x86-windows-nat.c
+++ b/gdb/x86-windows-nat.c
@@ -111,6 +111,7 @@ x86_windows_nat_target::fill_thread_context (windows_thread_info *th)
     {
       if (context->ContextFlags == 0)
 	{
+	  th->suspend ();
 	  context->ContextFlags = WindowsContext<decltype(context)>::all;
 	  CHECK (get_thread_context (th->h, context));
 	}
@@ -254,6 +255,7 @@ x86_windows_nat_target::store_one_register (const struct regcache *regcache,
 
   char *context_ptr = x86_windows_process.with_context (th, [] (auto *context)
     {
+      gdb_assert (context->ContextFlags != 0);
       return (char *) context;
     });
 
diff --git a/gdbserver/win32-low.cc b/gdbserver/win32-low.cc
index d6d7acf599d..180fabe0df9 100644
--- a/gdbserver/win32-low.cc
+++ b/gdbserver/win32-low.cc
@@ -432,9 +432,8 @@ static void
 child_fetch_inferior_registers (struct regcache *regcache, int r)
 {
   int regno;
-  windows_thread_info *th
-    = windows_process.thread_rec (current_thread->id,
-				  INVALIDATE_CONTEXT);
+  windows_thread_info *th = windows_process.find_thread (current_thread->id);
+  win32_require_context (th);
   if (r == -1 || r > NUM_REGS)
     child_fetch_inferior_registers (regcache, NUM_REGS);
   else
@@ -448,9 +447,8 @@ static void
 child_store_inferior_registers (struct regcache *regcache, int r)
 {
   int regno;
-  windows_thread_info *th
-    = windows_process.thread_rec (current_thread->id,
-				  INVALIDATE_CONTEXT);
+  windows_thread_info *th = windows_process.find_thread (current_thread->id);
+  win32_require_context (th);
   if (r == -1 || r == 0 || r > NUM_REGS)
     child_store_inferior_registers (regcache, NUM_REGS);
   else