ceph/src/mgr/Gil.cc

   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
  16 #include "Python.h"
  17
  18 #include "common/debug.h"
  19
  20 #define dout_context g_ceph_context
  21 #define dout_subsys ceph_subsys_mgr
  22 #undef dout_prefix
  23 #define dout_prefix *_dout << "mgr " << __func__ << " "
  24
  25 #include "Gil.h"
  26
  27 SafeThreadState::SafeThreadState(PyThreadState *ts_)
  28     : ts(ts_)
  29 {
  30   ceph_assert(ts != nullptr);
  31   thread = pthread_self();
  32 }
  33
  34 Gil::Gil(SafeThreadState &ts, bool new_thread) : pThreadState(ts)
  35 {
  36   // Acquire the GIL, set the current thread state
  37   PyEval_RestoreThread(pThreadState.ts);
  38   dout(25) << "GIL acquired for thread state " << pThreadState.ts << dendl;
  39
  40   //
  41   // If called from a separate OS thread (i.e. a thread not created
  42   // by Python, that does't already have a python thread state that
  43   // was created when that thread was active), we need to manually
  44   // create and switch to a python thread state specifically for this
  45   // OS thread.
  46   //
  47   // Note that instead of requring the caller to set new_thread == true
  48   // when calling this from a separate OS thread, we could figure out
  49   // if this was necessary automatically, as follows:
  50   //
  51   //   if (pThreadState->thread_id != PyThread_get_thread_ident()) {
  52   //
  53   // However, this means we're accessing pThreadState->thread_id, but
  54   // the Python C API docs say that "The only public data member is
  55   // PyInterpreterState *interp", i.e. doing this would violate
  56   // something that's meant to be a black box.
  57   //
  58   if (new_thread) {
  59     pNewThreadState = PyThreadState_New(pThreadState.ts->interp);
  60     PyThreadState_Swap(pNewThreadState);
  61     dout(20) << "Switched to new thread state " << pNewThreadState << dendl;
  62   } else {
  63     ceph_assert(pthread_self() == pThreadState.thread);
  64   }
  65 }
  66
  67 Gil::~Gil()
  68 {
  69   if (pNewThreadState != nullptr) {
  70     dout(20) << "Destroying new thread state " << pNewThreadState << dendl;
  71     PyThreadState_Swap(pThreadState.ts);
  72     PyThreadState_Clear(pNewThreadState);
  73     PyThreadState_Delete(pNewThreadState);
  74   }
  75   // Release the GIL, reset the thread state to NULL
  76   PyEval_SaveThread();
  77   dout(25) << "GIL released for thread state " << pThreadState.ts << dendl;
  78 }
  79
  80 without_gil_t::without_gil_t()
  81 {
  82   assert(PyGILState_Check());
  83   release_gil();
  84 }
  85
  86 without_gil_t::~without_gil_t()
  87 {
  88   if (save) {
  89     acquire_gil();
  90   }
  91 }
  92
  93 void without_gil_t::release_gil()
  94 {
  95   save = PyEval_SaveThread();
  96 }
  97
  98 void without_gil_t::acquire_gil()
  99 {
 100   assert(save);
 101   PyEval_RestoreThread(save);
 102   save = nullptr;
 103 }
 104
 105 with_gil_t::with_gil_t(without_gil_t& allow_threads)
 106   : allow_threads{allow_threads}
 107 {
 108   allow_threads.acquire_gil();
 109 }
 110
 111 with_gil_t::~with_gil_t()
 112 {
 113   allow_threads.release_gil();
 114 }