330 lines
14 KiB
C++
330 lines
14 KiB
C++
// Ceres Solver - A fast non-linear least squares minimizer
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// Copyright 2015 Google Inc. All rights reserved.
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// http://ceres-solver.org/
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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 met:
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//
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// * Redistributions of source code must retain the above copyright notice,
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// this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above copyright notice,
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// this list of conditions and the following disclaimer in the documentation
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// and/or other materials provided with the distribution.
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// * Neither the name of Google Inc. nor the names of its contributors may be
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// used to endorse or promote products derived from this software without
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// specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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// POSSIBILITY OF SUCH DAMAGE.
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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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// 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 CERES_INTERNAL_MUTEX_H_
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#define CERES_INTERNAL_MUTEX_H_
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#include "ceres/internal/port.h"
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#if defined(CERES_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 CERES_WIN32_LEAN_AND_MEAN // We only need minimal includes
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# ifdef CERES_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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// Unfortunately, windows.h defines a bunch of macros with common
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// names. Two in particular need avoiding: ERROR and min/max.
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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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# ifndef NOMINMAX
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# define NOMINMAX
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# endif
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# include <windows.h>
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typedef CRITICAL_SECTION MutexType;
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#elif defined(CERES_HAVE_PTHREAD) && defined(CERES_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 CERES_HAVE_RWLOCK (at least on linux --
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// it *does* cause problems for FreeBSD, or MacOSX, but isn't needed for
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// locking there.)
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# if defined(__linux__) && !defined(_XOPEN_SOURCE)
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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(CERES_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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namespace ceres {
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namespace internal {
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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 CERES_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(CERES_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 CERES_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(CERES_HAVE_PTHREAD) && defined(CERES_HAVE_RWLOCK)
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#define CERES_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() { CERES_SAFE_PTHREAD(pthread_rwlock_destroy); }
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void Mutex::Lock() { CERES_SAFE_PTHREAD(pthread_rwlock_wrlock); }
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void Mutex::Unlock() { CERES_SAFE_PTHREAD(pthread_rwlock_unlock); }
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#ifdef CERES_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() { CERES_SAFE_PTHREAD(pthread_rwlock_rdlock); }
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void Mutex::ReaderUnlock() { CERES_SAFE_PTHREAD(pthread_rwlock_unlock); }
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#undef CERES_SAFE_PTHREAD
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#elif defined(CERES_HAVE_PTHREAD)
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#define CERES_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() { CERES_SAFE_PTHREAD(pthread_mutex_destroy); }
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void Mutex::Lock() { CERES_SAFE_PTHREAD(pthread_mutex_lock); }
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void Mutex::Unlock() { CERES_SAFE_PTHREAD(pthread_mutex_unlock); }
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#ifdef CERES_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 CERES_SAFE_PTHREAD
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#endif
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// --------------------------------------------------------------------------
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// Some helper classes
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// Note: The weird "Ceres" prefix for the class is a workaround for having two
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// similar mutex.h files included in the same translation unit. This is a
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// problem because macros do not respect C++ namespaces, and as a result, this
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// does not work well (e.g. inside Chrome). The offending macros are
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// "MutexLock(x) COMPILE_ASSERT(false)". To work around this, "Ceres" is
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// prefixed to the class names; this permits defining the classes.
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// CeresMutexLock(mu) acquires mu when constructed and releases it
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// when destroyed.
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class CeresMutexLock {
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public:
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explicit CeresMutexLock(Mutex *mu) : mu_(mu) { mu_->Lock(); }
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~CeresMutexLock() { 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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CeresMutexLock(const CeresMutexLock&);
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void operator=(const CeresMutexLock&);
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};
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// CeresReaderMutexLock and CeresWriterMutexLock do the same, for rwlocks
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class CeresReaderMutexLock {
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public:
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explicit CeresReaderMutexLock(Mutex *mu) : mu_(mu) { mu_->ReaderLock(); }
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~CeresReaderMutexLock() { 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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CeresReaderMutexLock(const CeresReaderMutexLock&);
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void operator=(const CeresReaderMutexLock&);
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};
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class CeresWriterMutexLock {
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public:
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explicit CeresWriterMutexLock(Mutex *mu) : mu_(mu) { mu_->WriterLock(); }
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~CeresWriterMutexLock() { 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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CeresWriterMutexLock(const CeresWriterMutexLock&);
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void operator=(const CeresWriterMutexLock&);
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};
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// Catch bug where variable name is omitted, e.g. MutexLock (&mu);
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#define CeresMutexLock(x) \
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COMPILE_ASSERT(0, ceres_mutex_lock_decl_missing_var_name)
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#define CeresReaderMutexLock(x) \
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COMPILE_ASSERT(0, ceres_rmutex_lock_decl_missing_var_name)
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#define CeresWriterMutexLock(x) \
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COMPILE_ASSERT(0, ceres_wmutex_lock_decl_missing_var_name)
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} // namespace internal
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} // namespace ceres
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#endif // CERES_INTERNAL_MUTEX_H_
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