ceph/src/mgr/Gil.h

   1 // -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
   2 // vim: ts=8 sw=2 smarttab
   3 /*
   4  * Ceph - scalable distributed file system
   5  *
   6  * Copyright (C) 2017 SUSE LLC
   7  *
   8  * This is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License version 2.1, as published by the Free Software
  11  * Foundation.  See file COPYING.
  12  *
  13  */
  14
  15 #pragma once
  16
  17 struct _ts;
  18 typedef struct _ts PyThreadState;
  19
  20 #include <pthread.h>
  21
  22
  23 /**
  24  * Wrap PyThreadState to carry a record of which POSIX thread
  25  * the thread state relates to.  This allows the Gil class to
  26  * validate that we're being used from the right thread.
  27  */
  28 class SafeThreadState
  29 {
  30   public:
  31   explicit SafeThreadState(PyThreadState *ts_);
  32
  33   SafeThreadState()
  34     : ts(nullptr), thread(0)
  35   {
  36   }
  37
  38   PyThreadState *ts;
  39   pthread_t thread;
  40
  41   void set(PyThreadState *ts_)
  42   {
  43     ts = ts_;
  44     thread = pthread_self();
  45   }
  46 };
  47
  48 //
  49 // Use one of these in any scope in which you need to hold Python's
  50 // Global Interpreter Lock.
  51 //
  52 // Do *not* nest these, as a second GIL acquire will deadlock (see
  53 // https://docs.python.org/2/c-api/init.html#c.PyEval_RestoreThread)
  54 //
  55 // If in doubt, explicitly put a scope around the block of code you
  56 // know you need the GIL in.
  57 //
  58 // See the comment in Gil::Gil for when to set new_thread == true
  59 //
  60 class Gil {
  61 public:
  62   Gil(const Gil&) = delete;
  63   Gil& operator=(const Gil&) = delete;
  64
  65   Gil(SafeThreadState &ts, bool new_thread = false);
  66   ~Gil();
  67
  68 private:
  69   SafeThreadState &pThreadState;
  70   PyThreadState *pNewThreadState = nullptr;
  71 };
  72