mirror of https://github.com/odrling/Aegisub
Add Googles mutex.h which seems to be used in many of googles projects. It's better to use something that's well-tested rather than rolling our own. Also a huge time saver.
Originally committed to SVN as r4372.
This commit is contained in:
Amar Takhar
parent
9393850884
commit
9d0c5a4890
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@ -262,6 +262,19 @@ AC_SUBST(DMG_STRING)
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ACX_PTHREAD([], [AC_MSG_FAILURE([You must have working pthreads.])])
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CC="$PTHREAD_CC";
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AC_AGI_COMPILE([pthread_rwlock_*], [pthread_rwlock], [$PTHREAD_CFLAGS], [$PTHREAD_LIBS],[
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#include <pthread.h>
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#define _XOPEN_SOURCE 500
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int main(void) {
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pthread_rwlock_t l; pthread_rwlock_init(&l, NULL);
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pthread_rwlock_rdlock(&l);
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return 0;
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}])
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if test "$agi_cv_with_pthread_rwlock" = "yes"; then
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AC_DEFINE(HAVE_RWLOCK,1,[define if the compiler implements pthread_rwlock_*])
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fi
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######################
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# Check compiler flags
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@ -24,6 +24,7 @@
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#include <string.h>
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#include "libaegisub/log.h"
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#include "libaegisub/mutex.h"
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namespace agi {
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namespace log {
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@ -0,0 +1,11 @@
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#ifndef AGI_PRE
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#ifdef _WIN32 // Windows specific settings
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#define HAVE_PTHREAD 1
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#else
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// Generated by configure.in
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#include "../acconf.h"
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#endif // _WIN32
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#endif // LAGI_PRE
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@ -0,0 +1,325 @@
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// Copyright (c) 2007, Google Inc.
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following disclaimer
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// in the documentation and/or other materials provided with the
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// distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived from
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// this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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//
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// ---
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// Author: Craig Silverstein.
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//
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// A simple mutex wrapper, supporting locks and read-write locks.
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// You should assume the locks are *not* re-entrant.
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//
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// To use: you should define the following macros in your configure.ac:
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// ACX_PTHREAD
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// AC_RWLOCK
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// The latter is defined in ../autoconf.
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//
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// This class is meant to be internal-only and should be wrapped by an
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// internal namespace. Before you use this module, please give the
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// name of your internal namespace for this module. Or, if you want
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// to expose it, you'll want to move it to the Google namespace. We
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// cannot put this class in global namespace because there can be some
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// problems when we have multiple versions of Mutex in each shared object.
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//
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// NOTE: by default, we have #ifdef'ed out the TryLock() method.
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// This is for two reasons:
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// 1) TryLock() under Windows is a bit annoying (it requires a
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// #define to be defined very early).
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// 2) TryLock() is broken for NO_THREADS mode, at least in NDEBUG
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// mode.
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// If you need TryLock(), and either these two caveats are not a
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// problem for you, or you're willing to work around them, then
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// feel free to #define GMUTEX_TRYLOCK, or to remove the #ifdefs
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// in the code below.
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//
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// CYGWIN NOTE: Cygwin support for rwlock seems to be buggy:
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// http://www.cygwin.com/ml/cygwin/2008-12/msg00017.html
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// Because of that, we might as well use windows locks for
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// cygwin. They seem to be more reliable than the cygwin pthreads layer.
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//
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// TRICKY IMPLEMENTATION NOTE:
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// This class is designed to be safe to use during
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// dynamic-initialization -- that is, by global constructors that are
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// run before main() starts. The issue in this case is that
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// dynamic-initialization happens in an unpredictable order, and it
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// could be that someone else's dynamic initializer could call a
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// function that tries to acquire this mutex -- but that all happens
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// before this mutex's constructor has run. (This can happen even if
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// the mutex and the function that uses the mutex are in the same .cc
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// file.) Basically, because Mutex does non-trivial work in its
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// constructor, it's not, in the naive implementation, safe to use
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// before dynamic initialization has run on it.
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//
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// The solution used here is to pair the actual mutex primitive with a
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// bool that is set to true when the mutex is dynamically initialized.
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// (Before that it's false.) Then we modify all mutex routines to
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// look at the bool, and not try to lock/unlock until the bool makes
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// it to true (which happens after the Mutex constructor has run.)
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//
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// This works because before main() starts -- particularly, during
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// dynamic initialization -- there are no threads, so a) it's ok that
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// the mutex operations are a no-op, since we don't need locking then
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// anyway; and b) we can be quite confident our bool won't change
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// state between a call to Lock() and a call to Unlock() (that would
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// require a global constructor in one translation unit to call Lock()
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// and another global constructor in another translation unit to call
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// Unlock() later, which is pretty perverse).
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//
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// That said, it's tricky, and can conceivably fail; it's safest to
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// avoid trying to acquire a mutex in a global constructor, if you
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// can. One way it can fail is that a really smart compiler might
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// initialize the bool to true at static-initialization time (too
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// early) rather than at dynamic-initialization time. To discourage
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// that, we set is_safe_ to true in code (not the constructor
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// colon-initializer) and set it to true via a function that always
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// evaluates to true, but that the compiler can't know always
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// evaluates to true. This should be good enough.
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#ifndef GOOGLE_MUTEX_H_
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#define GOOGLE_MUTEX_H_
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#include "../../config.h" // to figure out pthreads support
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#if defined(NO_THREADS)
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typedef int MutexType; // to keep a lock-count
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#elif defined(_WIN32) || defined(__CYGWIN32__) || defined(__CYGWIN64__)
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# define WIN32_LEAN_AND_MEAN // We only need minimal includes
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# ifdef GMUTEX_TRYLOCK
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// We need Windows NT or later for TryEnterCriticalSection(). If you
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// don't need that functionality, you can remove these _WIN32_WINNT
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// lines, and change TryLock() to assert(0) or something.
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# ifndef _WIN32_WINNT
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# define _WIN32_WINNT 0x0400
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# endif
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# endif
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// To avoid macro definition of ERROR.
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# define NOGDI
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// To avoid macro definition of min/max.
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# define NOMINMAX
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# include <windows.h>
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typedef CRITICAL_SECTION MutexType;
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#elif defined(HAVE_PTHREAD) && defined(HAVE_RWLOCK)
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// Needed for pthread_rwlock_*. If it causes problems, you could take it
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// out, but then you'd have to unset HAVE_RWLOCK (at least on linux -- it
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// *does* cause problems for FreeBSD, or MacOSX, but isn't needed
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// for locking there.)
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# ifdef __linux__
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# define _XOPEN_SOURCE 500 // may be needed to get the rwlock calls
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# endif
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# include <pthread.h>
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typedef pthread_rwlock_t MutexType;
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#elif defined(HAVE_PTHREAD)
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# include <pthread.h>
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typedef pthread_mutex_t MutexType;
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#else
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# error Need to implement mutex.h for your architecture, or #define NO_THREADS
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#endif
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// We need to include these header files after defining _XOPEN_SOURCE
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// as they may define the _XOPEN_SOURCE macro.
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#include <assert.h>
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#include <stdlib.h> // for abort()
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#define MUTEX_NAMESPACE glog_internal_namespace_
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namespace MUTEX_NAMESPACE {
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class Mutex {
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public:
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// Create a Mutex that is not held by anybody. This constructor is
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// typically used for Mutexes allocated on the heap or the stack.
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// See below for a recommendation for constructing global Mutex
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// objects.
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inline Mutex();
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// Destructor
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inline ~Mutex();
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inline void Lock(); // Block if needed until free then acquire exclusively
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inline void Unlock(); // Release a lock acquired via Lock()
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#ifdef GMUTEX_TRYLOCK
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inline bool TryLock(); // If free, Lock() and return true, else return false
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#endif
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// Note that on systems that don't support read-write locks, these may
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// be implemented as synonyms to Lock() and Unlock(). So you can use
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// these for efficiency, but don't use them anyplace where being able
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// to do shared reads is necessary to avoid deadlock.
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inline void ReaderLock(); // Block until free or shared then acquire a share
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inline void ReaderUnlock(); // Release a read share of this Mutex
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inline void WriterLock() { Lock(); } // Acquire an exclusive lock
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inline void WriterUnlock() { Unlock(); } // Release a lock from WriterLock()
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// TODO(hamaji): Do nothing, implement correctly.
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inline void AssertHeld() {}
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private:
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MutexType mutex_;
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// We want to make sure that the compiler sets is_safe_ to true only
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// when we tell it to, and never makes assumptions is_safe_ is
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// always true. volatile is the most reliable way to do that.
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volatile bool is_safe_;
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inline void SetIsSafe() { is_safe_ = true; }
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// Catch the error of writing Mutex when intending MutexLock.
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Mutex(Mutex* /*ignored*/) {}
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// Disallow "evil" constructors
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Mutex(const Mutex&);
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void operator=(const Mutex&);
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};
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// Now the implementation of Mutex for various systems
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#if defined(NO_THREADS)
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// When we don't have threads, we can be either reading or writing,
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// but not both. We can have lots of readers at once (in no-threads
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// mode, that's most likely to happen in recursive function calls),
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// but only one writer. We represent this by having mutex_ be -1 when
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// writing and a number > 0 when reading (and 0 when no lock is held).
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//
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// In debug mode, we assert these invariants, while in non-debug mode
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// we do nothing, for efficiency. That's why everything is in an
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// assert.
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Mutex::Mutex() : mutex_(0) { }
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Mutex::~Mutex() { assert(mutex_ == 0); }
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void Mutex::Lock() { assert(--mutex_ == -1); }
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void Mutex::Unlock() { assert(mutex_++ == -1); }
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#ifdef GMUTEX_TRYLOCK
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bool Mutex::TryLock() { if (mutex_) return false; Lock(); return true; }
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#endif
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void Mutex::ReaderLock() { assert(++mutex_ > 0); }
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void Mutex::ReaderUnlock() { assert(mutex_-- > 0); }
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#elif defined(_WIN32) || defined(__CYGWIN32__) || defined(__CYGWIN64__)
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Mutex::Mutex() { InitializeCriticalSection(&mutex_); SetIsSafe(); }
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Mutex::~Mutex() { DeleteCriticalSection(&mutex_); }
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void Mutex::Lock() { if (is_safe_) EnterCriticalSection(&mutex_); }
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void Mutex::Unlock() { if (is_safe_) LeaveCriticalSection(&mutex_); }
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#ifdef GMUTEX_TRYLOCK
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bool Mutex::TryLock() { return is_safe_ ?
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TryEnterCriticalSection(&mutex_) != 0 : true; }
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#endif
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void Mutex::ReaderLock() { Lock(); } // we don't have read-write locks
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void Mutex::ReaderUnlock() { Unlock(); }
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#elif defined(HAVE_PTHREAD) && defined(HAVE_RWLOCK)
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#define SAFE_PTHREAD(fncall) do { /* run fncall if is_safe_ is true */ \
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if (is_safe_ && fncall(&mutex_) != 0) abort(); \
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} while (0)
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Mutex::Mutex() {
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SetIsSafe();
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if (is_safe_ && pthread_rwlock_init(&mutex_, NULL) != 0) abort();
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}
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Mutex::~Mutex() { SAFE_PTHREAD(pthread_rwlock_destroy); }
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void Mutex::Lock() { SAFE_PTHREAD(pthread_rwlock_wrlock); }
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void Mutex::Unlock() { SAFE_PTHREAD(pthread_rwlock_unlock); }
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#ifdef GMUTEX_TRYLOCK
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bool Mutex::TryLock() { return is_safe_ ?
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pthread_rwlock_trywrlock(&mutex_) == 0 :
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true; }
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#endif
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void Mutex::ReaderLock() { SAFE_PTHREAD(pthread_rwlock_rdlock); }
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void Mutex::ReaderUnlock() { SAFE_PTHREAD(pthread_rwlock_unlock); }
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#undef SAFE_PTHREAD
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#elif defined(HAVE_PTHREAD)
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#define SAFE_PTHREAD(fncall) do { /* run fncall if is_safe_ is true */ \
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if (is_safe_ && fncall(&mutex_) != 0) abort(); \
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} while (0)
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Mutex::Mutex() {
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SetIsSafe();
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if (is_safe_ && pthread_mutex_init(&mutex_, NULL) != 0) abort();
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}
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Mutex::~Mutex() { SAFE_PTHREAD(pthread_mutex_destroy); }
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void Mutex::Lock() { SAFE_PTHREAD(pthread_mutex_lock); }
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void Mutex::Unlock() { SAFE_PTHREAD(pthread_mutex_unlock); }
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#ifdef GMUTEX_TRYLOCK
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bool Mutex::TryLock() { return is_safe_ ?
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pthread_mutex_trylock(&mutex_) == 0 : true; }
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#endif
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void Mutex::ReaderLock() { Lock(); }
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void Mutex::ReaderUnlock() { Unlock(); }
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#undef SAFE_PTHREAD
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#endif
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// --------------------------------------------------------------------------
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// Some helper classes
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// MutexLock(mu) acquires mu when constructed and releases it when destroyed.
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class MutexLock {
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public:
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explicit MutexLock(Mutex *mu) : mu_(mu) { mu_->Lock(); }
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~MutexLock() { mu_->Unlock(); }
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private:
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Mutex * const mu_;
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// Disallow "evil" constructors
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MutexLock(const MutexLock&);
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void operator=(const MutexLock&);
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};
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// ReaderMutexLock and WriterMutexLock do the same, for rwlocks
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class ReaderMutexLock {
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public:
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explicit ReaderMutexLock(Mutex *mu) : mu_(mu) { mu_->ReaderLock(); }
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~ReaderMutexLock() { mu_->ReaderUnlock(); }
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private:
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Mutex * const mu_;
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// Disallow "evil" constructors
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ReaderMutexLock(const ReaderMutexLock&);
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void operator=(const ReaderMutexLock&);
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};
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class WriterMutexLock {
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public:
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explicit WriterMutexLock(Mutex *mu) : mu_(mu) { mu_->WriterLock(); }
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~WriterMutexLock() { mu_->WriterUnlock(); }
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private:
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Mutex * const mu_;
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// Disallow "evil" constructors
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WriterMutexLock(const WriterMutexLock&);
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void operator=(const WriterMutexLock&);
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};
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// Catch bug where variable name is omitted, e.g. MutexLock (&mu);
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#define MutexLock(x) COMPILE_ASSERT(0, mutex_lock_decl_missing_var_name)
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#define ReaderMutexLock(x) COMPILE_ASSERT(0, rmutex_lock_decl_missing_var_name)
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#define WriterMutexLock(x) COMPILE_ASSERT(0, wmutex_lock_decl_missing_var_name)
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} // namespace MUTEX_NAMESPACE
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using namespace MUTEX_NAMESPACE;
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#undef MUTEX_NAMESPACE
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#endif /* #define GOOGLE_MUTEX_H__ */
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