mirror of
https://sourceware.org/git/binutils-gdb.git
synced 2024-12-27 04:52:05 +08:00
213516ef31
This commit is the result of running the gdb/copyright.py script, which automated the update of the copyright year range for all source files managed by the GDB project to be updated to include year 2023.
249 lines
6.3 KiB
C++
249 lines
6.3 KiB
C++
/* Thread pool
|
|
|
|
Copyright (C) 2019-2023 Free Software Foundation, Inc.
|
|
|
|
This file is part of GDB.
|
|
|
|
This program is free software; you can redistribute it and/or modify
|
|
it under the terms of the GNU General Public License as published by
|
|
the Free Software Foundation; either version 3 of the License, or
|
|
(at your option) any later version.
|
|
|
|
This program is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
GNU General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with this program. If not, see <http://www.gnu.org/licenses/>. */
|
|
|
|
#include "common-defs.h"
|
|
#include "gdbsupport/thread-pool.h"
|
|
|
|
#if CXX_STD_THREAD
|
|
|
|
#include "gdbsupport/alt-stack.h"
|
|
#include "gdbsupport/block-signals.h"
|
|
#include <algorithm>
|
|
#include <system_error>
|
|
|
|
/* On the off chance that we have the pthread library on a Windows
|
|
host, but std::thread is not using it, avoid calling
|
|
pthread_setname_np on Windows. */
|
|
#ifndef _WIN32
|
|
#ifdef HAVE_PTHREAD_SETNAME_NP
|
|
#define USE_PTHREAD_SETNAME_NP
|
|
#endif
|
|
#endif
|
|
|
|
#ifdef USE_PTHREAD_SETNAME_NP
|
|
|
|
#include <pthread.h>
|
|
|
|
/* Handle platform discrepancies in pthread_setname_np: macOS uses a
|
|
single-argument form, while Linux uses a two-argument form. NetBSD
|
|
takes a printf-style format and an argument. This wrapper handles the
|
|
difference. */
|
|
|
|
ATTRIBUTE_UNUSED static void
|
|
do_set_thread_name (int (*set_name) (pthread_t, const char *, void *),
|
|
const char *name)
|
|
{
|
|
set_name (pthread_self (), "%s", const_cast<char *> (name));
|
|
}
|
|
|
|
ATTRIBUTE_UNUSED static void
|
|
do_set_thread_name (int (*set_name) (pthread_t, const char *),
|
|
const char *name)
|
|
{
|
|
set_name (pthread_self (), name);
|
|
}
|
|
|
|
/* The macOS man page says that pthread_setname_np returns "void", but
|
|
the headers actually declare it returning "int". */
|
|
ATTRIBUTE_UNUSED static void
|
|
do_set_thread_name (int (*set_name) (const char *), const char *name)
|
|
{
|
|
set_name (name);
|
|
}
|
|
|
|
static void
|
|
set_thread_name (const char *name)
|
|
{
|
|
do_set_thread_name (pthread_setname_np, name);
|
|
}
|
|
|
|
#elif defined (USE_WIN32API)
|
|
|
|
#include <windows.h>
|
|
|
|
typedef HRESULT WINAPI (SetThreadDescription_ftype) (HANDLE, PCWSTR);
|
|
static SetThreadDescription_ftype *dyn_SetThreadDescription;
|
|
static bool initialized;
|
|
|
|
static void
|
|
init_windows ()
|
|
{
|
|
initialized = true;
|
|
|
|
HMODULE hm = LoadLibrary (TEXT ("kernel32.dll"));
|
|
if (hm)
|
|
dyn_SetThreadDescription
|
|
= (SetThreadDescription_ftype *) GetProcAddress (hm,
|
|
"SetThreadDescription");
|
|
|
|
/* On some versions of Windows, this function is only available in
|
|
KernelBase.dll, not kernel32.dll. */
|
|
if (dyn_SetThreadDescription == nullptr)
|
|
{
|
|
hm = LoadLibrary (TEXT ("KernelBase.dll"));
|
|
if (hm)
|
|
dyn_SetThreadDescription
|
|
= (SetThreadDescription_ftype *) GetProcAddress (hm,
|
|
"SetThreadDescription");
|
|
}
|
|
}
|
|
|
|
static void
|
|
do_set_thread_name (const wchar_t *name)
|
|
{
|
|
if (!initialized)
|
|
init_windows ();
|
|
|
|
if (dyn_SetThreadDescription != nullptr)
|
|
dyn_SetThreadDescription (GetCurrentThread (), name);
|
|
}
|
|
|
|
#define set_thread_name(NAME) do_set_thread_name (L ## NAME)
|
|
|
|
#else /* USE_WIN32API */
|
|
|
|
static void
|
|
set_thread_name (const char *name)
|
|
{
|
|
}
|
|
|
|
#endif
|
|
|
|
#endif /* CXX_STD_THREAD */
|
|
|
|
namespace gdb
|
|
{
|
|
|
|
/* The thread pool detach()s its threads, so that the threads will not
|
|
prevent the process from exiting. However, it was discovered that
|
|
if any detached threads were still waiting on a condition variable,
|
|
then the condition variable's destructor would wait for the threads
|
|
to exit -- defeating the purpose.
|
|
|
|
Allocating the thread pool on the heap and simply "leaking" it
|
|
avoids this problem.
|
|
*/
|
|
thread_pool *thread_pool::g_thread_pool = new thread_pool ();
|
|
|
|
thread_pool::~thread_pool ()
|
|
{
|
|
/* Because this is a singleton, we don't need to clean up. The
|
|
threads are detached so that they won't prevent process exit.
|
|
And, cleaning up here would be actively harmful in at least one
|
|
case -- see the comment by the definition of g_thread_pool. */
|
|
}
|
|
|
|
void
|
|
thread_pool::set_thread_count (size_t num_threads)
|
|
{
|
|
#if CXX_STD_THREAD
|
|
std::lock_guard<std::mutex> guard (m_tasks_mutex);
|
|
|
|
/* If the new size is larger, start some new threads. */
|
|
if (m_thread_count < num_threads)
|
|
{
|
|
/* Ensure that signals used by gdb are blocked in the new
|
|
threads. */
|
|
block_signals blocker;
|
|
for (size_t i = m_thread_count; i < num_threads; ++i)
|
|
{
|
|
try
|
|
{
|
|
std::thread thread (&thread_pool::thread_function, this);
|
|
thread.detach ();
|
|
}
|
|
catch (const std::system_error &)
|
|
{
|
|
/* libstdc++ may not implement std::thread, and will
|
|
throw an exception on use. It seems fine to ignore
|
|
this, and any other sort of startup failure here. */
|
|
num_threads = i;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
/* If the new size is smaller, terminate some existing threads. */
|
|
if (num_threads < m_thread_count)
|
|
{
|
|
for (size_t i = num_threads; i < m_thread_count; ++i)
|
|
m_tasks.emplace ();
|
|
m_tasks_cv.notify_all ();
|
|
}
|
|
|
|
m_thread_count = num_threads;
|
|
#else
|
|
/* No threads available, simply ignore the request. */
|
|
#endif /* CXX_STD_THREAD */
|
|
}
|
|
|
|
#if CXX_STD_THREAD
|
|
|
|
void
|
|
thread_pool::do_post_task (std::packaged_task<void ()> &&func)
|
|
{
|
|
std::packaged_task<void ()> t (std::move (func));
|
|
|
|
if (m_thread_count != 0)
|
|
{
|
|
std::lock_guard<std::mutex> guard (m_tasks_mutex);
|
|
m_tasks.emplace (std::move (t));
|
|
m_tasks_cv.notify_one ();
|
|
}
|
|
else
|
|
{
|
|
/* Just execute it now. */
|
|
t ();
|
|
}
|
|
}
|
|
|
|
void
|
|
thread_pool::thread_function ()
|
|
{
|
|
/* This must be done here, because on macOS one can only set the
|
|
name of the current thread. */
|
|
set_thread_name ("gdb worker");
|
|
|
|
/* Ensure that SIGSEGV is delivered to an alternate signal
|
|
stack. */
|
|
gdb::alternate_signal_stack signal_stack;
|
|
|
|
while (true)
|
|
{
|
|
optional<task_t> t;
|
|
|
|
{
|
|
/* We want to hold the lock while examining the task list, but
|
|
not while invoking the task function. */
|
|
std::unique_lock<std::mutex> guard (m_tasks_mutex);
|
|
while (m_tasks.empty ())
|
|
m_tasks_cv.wait (guard);
|
|
t = std::move (m_tasks.front());
|
|
m_tasks.pop ();
|
|
}
|
|
|
|
if (!t.has_value ())
|
|
break;
|
|
(*t) ();
|
|
}
|
|
}
|
|
|
|
#endif /* CXX_STD_THREAD */
|
|
|
|
} /* namespace gdb */
|