[PATCH v2 08/47] Windows gdb+gdbserver: New find_thread, replaces thread_rec(DONT_INVALIDATE_CONTEXT)

Pedro Alves
2025-05-19T13:26:27Z

The goal of the next few patches is to eliminate thread_rec
completely. This is the first patch in that effort.

thread_rec(DONT_INVALIDATE_CONTEXT) is really just a thread lookup
with no side effects, so this adds a find_thread function that lets
you do that.

Approved-By: Tom Tromey <tom@tromey.com>
Change-Id: Ie486badce00e234b10caa478b066c34537103e3f
---
gdb/nat/windows-nat.c | 5 ++-
gdb/nat/windows-nat.h | 7 ++--
gdb/windows-nat.c | 74 +++++++++++++++++++++---------------------
gdbserver/win32-low.cc | 32 ++++++++++--------
gdbserver/win32-low.h | 1 +
5 files changed, 62 insertions(+), 57 deletions(-)

diff --git a/gdb/nat/windows-nat.c b/gdb/nat/windows-nat.c
index 7b0fbc53413..b68d99a2496 100644
--- a/gdb/nat/windows-nat.c
+++ b/gdb/nat/windows-nat.c
@@ -315,9 +315,8 @@ windows_process_info::handle_ms_vc_exception (const EXCEPTION_RECORD *rec)
if (named_thread_id == (DWORD) -1)
named_thread_id = current_event.dwThreadId;

- named_thread = thread_rec (ptid_t (current_event.dwProcessId,
- named_thread_id, 0),
- DONT_INVALIDATE_CONTEXT);
+ named_thread = find_thread (ptid_t (current_event.dwProcessId,
+ named_thread_id, 0));
if (named_thread != NULL)
{
int thread_name_len;
diff --git a/gdb/nat/windows-nat.h b/gdb/nat/windows-nat.h
index 806bd352705..b0e51e93fd0 100644
--- a/gdb/nat/windows-nat.h
+++ b/gdb/nat/windows-nat.h
@@ -111,9 +111,6 @@ struct windows_thread_info
/* Possible values to pass to 'thread_rec'. */
enum thread_disposition_type
{
- /* Do not invalidate the thread's context, and do not suspend the
- thread. */
- DONT_INVALIDATE_CONTEXT,
/* Invalidate the context, but do not suspend the thread. */
DONT_SUSPEND,
/* Invalidate the context and suspend the thread. */
@@ -184,6 +181,10 @@ struct windows_process_info
bool ignore_first_breakpoint = false;
#endif

+ /* Find a thread record given a thread id.
+
+ This function must be supplied by the embedding application. */
+ virtual windows_thread_info *find_thread (ptid_t ptid) = 0;

/* Find a thread record given a thread id. THREAD_DISPOSITION
controls whether the thread is suspended, and whether the context
diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index fbe36102e2e..5b00b341afa 100644
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -93,6 +93,7 @@ struct windows_solib

struct windows_per_inferior : public windows_process_info
{
+ windows_thread_info *find_thread (ptid_t ptid) override;
windows_thread_info *thread_rec (ptid_t ptid,
thread_disposition_type disposition) override;
int handle_output_debug_string (struct target_waitstatus *ourstatus) override;
@@ -250,8 +251,7 @@ struct windows_nat_target final : public x86_nat_target<inf_child_target>

bool stopped_by_sw_breakpoint () override
{
- windows_thread_info *th
- = windows_process.thread_rec (inferior_ptid, DONT_INVALIDATE_CONTEXT);
+ windows_thread_info *th = windows_process.find_thread (inferior_ptid);
return th->stopped_at_software_breakpoint;
}

@@ -508,34 +508,38 @@ windows_nat_target::wait_for_debug_event_main_thread (DEBUG_EVENT *event)
/* See nat/windows-nat.h. */

windows_thread_info *
-windows_per_inferior::thread_rec
- (ptid_t ptid, thread_disposition_type disposition)
+windows_per_inferior::find_thread (ptid_t ptid)
{
for (auto &th : thread_list)
if (th->tid == ptid.lwp ())
- {
- if (!th->suspended)
- {
- switch (disposition)
- {
- case DONT_INVALIDATE_CONTEXT:
- /* Nothing. */
- break;
- case INVALIDATE_CONTEXT:
- if (ptid.lwp () != current_event.dwThreadId)
- th->suspend ();
- th->reload_context = true;
- break;
- case DONT_SUSPEND:
- th->reload_context = true;
- th->suspended = -1;
- break;
- }
- }
- return th.get ();
- }
+ return th.get ();
+ return nullptr;
+}
+
+/* See nat/windows-nat.h. */
+
+windows_thread_info *
+windows_per_inferior::thread_rec (ptid_t ptid,
+ thread_disposition_type disposition)
+{
+ windows_thread_info *th = find_thread (ptid);

- return NULL;
+ if (th != nullptr && !th->suspended)
+ {
+ switch (disposition)
+ {
+ case INVALIDATE_CONTEXT:
+ if (ptid.lwp () != current_event.dwThreadId)
+ th->suspend ();
+ th->reload_context = true;
+ break;
+ case DONT_SUSPEND:
+ th->reload_context = true;
+ th->suspended = -1;
+ break;
+ }
+ }
+ return th;
}

/* Add a thread to the thread list.
@@ -554,7 +558,7 @@ windows_nat_target::add_thread (ptid_t ptid, HANDLE h, void *tlb,

gdb_assert (ptid.lwp () != 0);

- if ((th = windows_process.thread_rec (ptid, DONT_INVALIDATE_CONTEXT)))
+ if ((th = windows_process.find_thread (ptid)))
return th;

CORE_ADDR base = (CORE_ADDR) (uintptr_t) tlb;
@@ -1131,7 +1135,7 @@ display_selectors (const char * args, int from_tty)
}

windows_thread_info *current_windows_thread
- = windows_process.thread_rec (inferior_ptid, DONT_INVALIDATE_CONTEXT);
+ = windows_process.find_thread (inferior_ptid);

if (!args)
{
@@ -1350,7 +1354,7 @@ windows_nat_target::resume (ptid_t ptid, int step, enum gdb_signal sig)
ptid.pid (), (unsigned) ptid.lwp (), step, sig);

/* Get context for currently selected thread. */
- th = windows_process.thread_rec (inferior_ptid, DONT_INVALIDATE_CONTEXT);
+ th = windows_process.find_thread (inferior_ptid);
if (th)
{
windows_process.with_context (th, [&] (auto *context)
@@ -3029,7 +3033,7 @@ windows_nat_target::get_tib_address (ptid_t ptid, CORE_ADDR *addr)
{
windows_thread_info *th;

- th = windows_process.thread_rec (ptid, DONT_INVALIDATE_CONTEXT);
+ th = windows_process.find_thread (ptid);
if (th == NULL)
return false;

@@ -3050,9 +3054,7 @@ windows_nat_target::get_ada_task_ptid (long lwp, ULONGEST thread)
const char *
windows_nat_target::thread_name (struct thread_info *thr)
{
- windows_thread_info *th
- = windows_process.thread_rec (thr->ptid,
- DONT_INVALIDATE_CONTEXT);
+ windows_thread_info *th = windows_process.find_thread (thr->ptid);
return th->thread_name ();
}

@@ -3194,8 +3196,7 @@ cygwin_set_dr7 (unsigned long val)
static CORE_ADDR
cygwin_get_dr (int i)
{
- windows_thread_info *th
- = windows_process.thread_rec (inferior_ptid, DONT_INVALIDATE_CONTEXT);
+ windows_thread_info *th = windows_process.find_thread (inferior_ptid);

return windows_process.with_context (th, [&] (auto *context) -> CORE_ADDR
{
@@ -3247,8 +3248,7 @@ windows_nat_target::thread_alive (ptid_t ptid)
{
gdb_assert (ptid.lwp () != 0);

- windows_thread_info *th
- = windows_process.thread_rec (ptid, DONT_INVALIDATE_CONTEXT);
+ windows_thread_info *th = windows_process.find_thread (ptid);
return WaitForSingleObject (th->h, 0) != WAIT_OBJECT_0;
}

diff --git a/gdbserver/win32-low.cc b/gdbserver/win32-low.cc
index 61f124337a5..ea11c3b7795 100644
--- a/gdbserver/win32-low.cc
+++ b/gdbserver/win32-low.cc
@@ -123,6 +123,17 @@ win32_require_context (windows_thread_info *th)

/* See nat/windows-nat.h. */

+windows_thread_info *
+gdbserver_windows_process::find_thread (ptid_t ptid)
+{
+ thread_info *thread = find_thread_ptid (ptid);
+ if (thread == nullptr)
+ return nullptr;
+ return static_cast<windows_thread_info *> (thread->target_data ());
+}
+
+/* See nat/windows-nat.h. */
+
windows_thread_info *
gdbserver_windows_process::thread_rec
(ptid_t ptid, thread_disposition_type disposition)
@@ -132,8 +143,7 @@ gdbserver_windows_process::thread_rec
return NULL;

auto th = static_cast<windows_thread_info *> (thread->target_data ());
- if (disposition != DONT_INVALIDATE_CONTEXT)
- win32_require_context (th);
+ win32_require_context (th);
return th;
}

@@ -144,7 +154,7 @@ child_add_thread (DWORD pid, DWORD tid, HANDLE h, void *tlb)
windows_thread_info *th;
ptid_t ptid = ptid_t (pid, tid, 0);

- if ((th = windows_process.thread_rec (ptid, DONT_INVALIDATE_CONTEXT)))
+ if ((th = windows_process.find_thread (ptid)))
return th;

CORE_ADDR base = (CORE_ADDR) (uintptr_t) tlb;
@@ -798,7 +808,7 @@ win32_process_target::resume (thread_resume *resume_info, size_t n)

/* Get context for the currently selected thread. */
ptid = debug_event_ptid (&windows_process.current_event);
- th = windows_process.thread_rec (ptid, DONT_INVALIDATE_CONTEXT);
+ th = windows_process.find_thread (ptid);
if (th)
{
win32_prepare_to_resume (th);
@@ -944,8 +954,7 @@ maybe_adjust_pc ()
child_fetch_inferior_registers (regcache, -1);

windows_thread_info *th
- = windows_process.thread_rec (current_thread->id,
- DONT_INVALIDATE_CONTEXT);
+ = windows_process.find_thread (current_thread->id);
th->stopped_at_software_breakpoint = false;

if (windows_process.current_event.dwDebugEventCode == EXCEPTION_DEBUG_EVENT
@@ -1345,8 +1354,7 @@ win32_process_target::supports_get_tib_address ()
int
win32_process_target::get_tib_address (ptid_t ptid, CORE_ADDR *addr)
{
- windows_thread_info *th;
- th = windows_process.thread_rec (ptid, DONT_INVALIDATE_CONTEXT);
+ windows_thread_info *th = windows_process.find_thread (ptid);
if (th == NULL)
return 0;
if (addr != NULL)
@@ -1366,9 +1374,7 @@ win32_process_target::sw_breakpoint_from_kind (int kind, int *size)
bool
win32_process_target::stopped_by_sw_breakpoint ()
{
- windows_thread_info *th
- = windows_process.thread_rec (current_thread->id,
- DONT_INVALIDATE_CONTEXT);
+ windows_thread_info *th = windows_process.find_thread (current_thread->id);
return th == nullptr ? false : th->stopped_at_software_breakpoint;
}

@@ -1393,9 +1399,7 @@ win32_process_target::write_pc (struct regcache *regcache, CORE_ADDR pc)
const char *
win32_process_target::thread_name (ptid_t thread)
{
- windows_thread_info *th
- = windows_process.thread_rec (current_thread->id,
- DONT_INVALIDATE_CONTEXT);
+ windows_thread_info *th = windows_process.find_thread (current_thread->id);
return th->thread_name ();
}

diff --git a/gdbserver/win32-low.h b/gdbserver/win32-low.h
index a76ed9fad3f..fb757da9718 100644
--- a/gdbserver/win32-low.h
+++ b/gdbserver/win32-low.h
@@ -181,6 +181,7 @@ class win32_process_target : public process_stratum_target

struct gdbserver_windows_process : public windows_nat::windows_process_info
{
+ windows_nat::windows_thread_info *find_thread (ptid_t ptid) override;
windows_nat::windows_thread_info *thread_rec
(ptid_t ptid,
windows_nat::thread_disposition_type disposition) override;
--
2.49.0