include/comphelper/crashzone.hxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
   2 /*
   3  * This file is part of the LibreOffice project.
   4  *
   5  * This Source Code Form is subject to the terms of the Mozilla Public
   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   8  */
   9
  10 #ifndef INCLUDED_COMPHELPER_CRASHZONE_H
  11 #define INCLUDED_COMPHELPER_CRASHZONE_H
  12
  13 #include <sal/config.h>
  14
  15 #include <atomic>
  16 #include <csignal>
  17 #include <type_traits>
  18
  19 struct CrashWatchdogTimingsValues
  20 {
  21     /// delays to take various actions in 1/4 of a second increments.
  22     int mnDisableEntries;
  23     int const mnAbortAfter;
  24 };
  25
  26 /**
  27  * A generic class for detecting if a given crash or a lock-up came from a specific
  28  * area of code (such as OpenGL).
  29  * Use this helper to track that.
  30  * The class is a template so that there can be multiple instances of static variables.
  31  */
  32 template <typename Dummy> class CrashZone
  33 {
  34 // gnEnterCount and gnLeaveCount are accessed both from multiple threads (cf.
  35 // WatchdogThread::execute; so need to be of atomic type) and from signal handlers (cf.
  36 // VCLExceptionSignal_impl; so need to be of lock-free atomic type).  sig_atomic_t is chosen as
  37 // the underlying type under the assumption that it is most likely to lead to an atomic type
  38 // that is actually lock-free.  However, gnEnterCount and gnLeaveCount are both monotonically
  39 // increasing, so will eventually overflow, so the underlying type better be unsigned, which
  40 // sig_atomic_t is not guaranteed to be:
  41 #if !defined ARM32 || (defined ARM32 && defined __ARM_PCS_VFP)
  42     using AtomicCounter = std::atomic<std::make_unsigned_t<std::sig_atomic_t>>;
  43     static_assert(AtomicCounter::is_always_lock_free);
  44 #else
  45     using AtomicCounter = volatile std::make_unsigned_t<std::sig_atomic_t>;
  46 #endif
  47
  48     /// how many times have we entered a zone
  49     static inline AtomicCounter gnEnterCount = 0;
  50     /// how many times have we left a new zone
  51     static inline AtomicCounter gnLeaveCount = 0;
  52
  53 public:
  54     CrashZone() { enter(); }
  55     ~CrashZone() { leave(); }
  56     static bool isInZone() { return gnEnterCount != gnLeaveCount; }
  57     static const AtomicCounter& enterCount() { return gnEnterCount; }
  58     // prefer creating instances to manually calling enter()/leave()
  59     static void enter() { gnEnterCount++; }
  60     static void leave() { gnLeaveCount++; }
  61     // these should be implemented for each specific zone if needed
  62     // static void hardDisable();
  63     // static const CrashWatchdogTimingsValues& getCrashWatchdogTimingsValues();
  64     // static void checkDebug(int nUnchanged, const CrashWatchdogTimingsValues& aTimingValues);
  65     // static const char* name();
  66 };
  67
  68 #endif // INCLUDED_COMPHELPER_CRASHZONE_H
  69
  70 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */