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// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
// vim: ts=8 sw=2 smarttab
/*
* Ceph - scalable distributed file system
*
* Copyright (C) 2017 SUSE LLC
*
* This is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License version 2.1, as published by the Free Software
* Foundation. See file COPYING.
*
*/
#pragma once
#include <cassert>
#include <functional>
struct _ts;
typedef struct _ts PyThreadState;
#include <pthread.h>
/**
* Wrap PyThreadState to carry a record of which POSIX thread
* the thread state relates to. This allows the Gil class to
* validate that we're being used from the right thread.
*/
class SafeThreadState
{
public:
explicit SafeThreadState(PyThreadState *ts_);
SafeThreadState()
: ts(nullptr), thread(0)
{
}
PyThreadState *ts;
pthread_t thread;
void set(PyThreadState *ts_)
{
ts = ts_;
thread = pthread_self();
}
};
//
// Use one of these in any scope in which you need to hold Python's
// Global Interpreter Lock.
//
// Do *not* nest these, as a second GIL acquire will deadlock (see
// https://docs.python.org/2/c-api/init.html#c.PyEval_RestoreThread)
//
// If in doubt, explicitly put a scope around the block of code you
// know you need the GIL in.
//
// See the comment in Gil::Gil for when to set new_thread == true
//
class Gil {
public:
Gil(const Gil&) = delete;
Gil& operator=(const Gil&) = delete;
Gil(SafeThreadState &ts, bool new_thread = false);
~Gil();
private:
SafeThreadState &pThreadState;
PyThreadState *pNewThreadState = nullptr;
};
// because the Python runtime could relinquish the GIL when performing GC
// and re-acquire it afterwards, we should enforce following locking policy:
// 1. do not acquire locks when holding the GIL, use a without_gil or
// without_gil_t to guard the code which acquires non-gil locks.
// 2. always hold a GIL when calling python functions, for example, when
// constructing a PyFormatter instance.
//
// a wrapper that provides a convenient RAII-style mechinary for acquiring
// and releasing GIL, like the macros of Py_BEGIN_ALLOW_THREADS and
// Py_END_ALLOW_THREADS.
struct without_gil_t {
without_gil_t();
~without_gil_t();
void release_gil();
void acquire_gil();
private:
PyThreadState *save = nullptr;
friend struct with_gil_t;
};
struct with_gil_t {
with_gil_t(without_gil_t& allow_threads);
~with_gil_t();
private:
without_gil_t& allow_threads;
};
// invoke func with GIL acquired
template<typename Func>
auto with_gil(without_gil_t& no_gil, Func&& func) {
with_gil_t gil{no_gil};
return std::invoke(std::forward<Func>(func));
}
template<typename Func>
auto without_gil(Func&& func) {
without_gil_t no_gil;
return std::invoke(std::forward<Func>(func));
}
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