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Copyright 2008 Larry Gritz and the other authors and contributors.
All Rights Reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
* Neither the name of the software's owners nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
(This is the Modified BSD License)
*/
/////////////////////////////////////////////////////////////////////////
/// @file thread.h
///
/// @brief Wrappers and utilities for multithreading.
/////////////////////////////////////////////////////////////////////////
#ifndef OPENIMAGEIO_THREAD_H
#define OPENIMAGEIO_THREAD_H
#include "version.h"
#include "sysutil.h"
// defining NOMINMAX to prevent problems with std::min/std::max
// and std::numeric_limits<type>::min()/std::numeric_limits<type>::max()
// when boost include windows.h
#ifdef _MSC_VER
# define WIN32_LEAN_AND_MEAN
# define VC_EXTRALEAN
# ifndef NOMINMAX
# define NOMINMAX
# endif
#endif
#include <boost/version.hpp>
#if defined(__GNUC__) && (BOOST_VERSION == 104500)
// gcc reports errors inside some of the boost headers with boost 1.45
// See: https://svn.boost.org/trac/boost/ticket/4818
#pragma GCC diagnostic ignored "-Wunused-variable"
#endif
#include <boost/thread.hpp>
#include <boost/thread/tss.hpp>
#include <boost/version.hpp>
#if defined(__GNUC__) && (BOOST_VERSION == 104500)
// can't restore via push/pop in all versions of gcc (warning push/pop implemented for 4.6+ only)
#pragma GCC diagnostic error "-Wunused-variable"
#endif
#ifndef USE_TBB
# define USE_TBB 0
#endif
// Include files we need for atomic counters.
// Some day, we hope this is all replaced by use of std::atomic<>.
#if USE_TBB
# include <tbb/atomic.h>
# include <tbb/spin_mutex.h>
# define USE_TBB_ATOMIC 1
# define USE_TBB_SPINLOCK 1
#else
# define USE_TBB_ATOMIC 0
# define USE_TBB_SPINLOCK 0
#endif
#if defined(_MSC_VER) && !USE_TBB
# include <windows.h>
# include <winbase.h>
# pragma intrinsic (_InterlockedExchangeAdd)
# pragma intrinsic (_InterlockedCompareExchange)
# pragma intrinsic (_InterlockedCompareExchange64)
# pragma intrinsic (_ReadWriteBarrier)
# if defined(_WIN64)
# pragma intrinsic(_InterlockedExchangeAdd64)
# endif
// InterlockedExchangeAdd64 is not available for XP
# if defined(_WIN32_WINNT) && _WIN32_WINNT <= 0x0501
inline long long
InterlockedExchangeAdd64 (volatile long long *Addend, long long Value)
{
long long Old;
do {
Old = *Addend;
} while (_InterlockedCompareExchange64(Addend, Old + Value, Old) != Old);
return Old;
}
# endif
#endif
#if defined(__GNUC__) && (defined(_GLIBCXX_ATOMIC_BUILTINS) || (__GNUC__ * 100 + __GNUC_MINOR__ >= 401))
#define USE_GCC_ATOMICS
#endif
OIIO_NAMESPACE_ENTER
{
/// Null mutex that can be substituted for a real one to test how much
/// overhead is associated with a particular mutex.
class null_mutex {
public:
null_mutex () { }
~null_mutex () { }
void lock () { }
void unlock () { }
void lock_shared () { }
void unlock_shared () { }
bool try_lock () { return true; }
};
/// Null lock that can be substituted for a real one to test how much
/// overhead is associated with a particular lock.
template<typename T>
class null_lock {
public:
null_lock (T &m) { }
};
// Null thread-specific ptr that just wraps a single ordinary pointer
//
template<typename T>
class null_thread_specific_ptr {
public:
typedef void (*destructor_t)(T *);
null_thread_specific_ptr (destructor_t dest=NULL)
: m_ptr(NULL), m_dest(dest) { }
~null_thread_specific_ptr () { reset (NULL); }
T * get () { return m_ptr; }
void reset (T *newptr=NULL) {
if (m_ptr) {
if (m_dest)
(*m_dest) (m_ptr);
else
delete m_ptr;
}
m_ptr = newptr;
}
private:
T *m_ptr;
destructor_t m_dest;
};
#ifdef NOTHREADS
// Definitions that we use for debugging to turn off all mutexes, locks,
// and atomics in order to test the performance hit of our thread safety.
// Null thread-specific ptr that just wraps a single ordinary pointer
//
template<typename T>
class thread_specific_ptr {
public:
typedef void (*destructor_t)(T *);
thread_specific_ptr (destructor_t dest=NULL)
: m_ptr(NULL), m_dest(dest) { }
~thread_specific_ptr () { reset (NULL); }
T * get () { return m_ptr; }
void reset (T *newptr=NULL) {
if (m_ptr) {
if (m_dest)
(*m_dest) (m_ptr);
else
delete m_ptr;
}
m_ptr = newptr;
}
private:
T *m_ptr;
destructor_t m_dest;
};
typedef null_mutex mutex;
typedef null_mutex recursive_mutex;
typedef null_lock<mutex> lock_guard;
typedef null_lock<recursive_mutex> recursive_lock_guard;
#else
// Fairly modern Boost has all the mutex and lock types we need.
typedef boost::mutex mutex;
typedef boost::recursive_mutex recursive_mutex;
typedef boost::lock_guard< boost::mutex > lock_guard;
typedef boost::lock_guard< boost::recursive_mutex > recursive_lock_guard;
using boost::thread_specific_ptr;
#endif
/// Atomic version of: r = *at, *at += x, return r
/// For each of several architectures.
inline int
atomic_exchange_and_add (volatile int *at, int x)
{
#ifdef NOTHREADS
int r = *at; *at += x; return r;
#elif defined(USE_GCC_ATOMICS)
return __atomic_fetch_add ((int *)at, x, __ATOMIC_SEQ_CST);
#elif USE_TBB
atomic<int> *a = (atomic<int> *)at;
return a->fetch_and_add (x);
#elif defined(_MSC_VER)
// Windows
return _InterlockedExchangeAdd ((volatile LONG *)at, x);
#else
# error No atomics on this platform.
#endif
}
inline long long
atomic_exchange_and_add (volatile long long *at, long long x)
{
#ifdef NOTHREADS
long long r = *at; *at += x; return r;
#elif defined(USE_GCC_ATOMICS)
return __atomic_fetch_add (at, x, __ATOMIC_SEQ_CST);
#elif USE_TBB
atomic<long long> *a = (atomic<long long> *)at;
return a->fetch_and_add (x);
#elif defined(_MSC_VER)
// Windows
# if defined(_WIN64)
return _InterlockedExchangeAdd64 ((volatile LONGLONG *)at, x);
# else
return InterlockedExchangeAdd64 ((volatile LONGLONG *)at, x);
# endif
#else
# error No atomics on this platform.
#endif
}
/// Atomic version of:
/// if (*at == compareval) {
/// *at = newval; return true;
/// } else {
/// return false;
/// }
inline bool
atomic_compare_and_exchange (volatile int *at, int compareval, int newval)
{
#ifdef NOTHREADS
if (*at == compareval) {
*at = newval; return true;
} else {
return false;
}
#elif defined(USE_GCC_ATOMICS)
return __atomic_compare_exchange_n (at, &compareval, newval, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
#elif USE_TBB
atomic<int> *a = (atomic<int> *)at;
return a->compare_and_swap (newval, compareval) == newval;
#elif defined(_MSC_VER)
return (_InterlockedCompareExchange ((volatile LONG *)at, newval, compareval) == compareval);
#else
# error No atomics on this platform.
#endif
}
inline bool
atomic_compare_and_exchange (volatile long long *at, long long compareval, long long newval)
{
#ifdef NOTHREADS
if (*at == compareval) {
*at = newval; return true;
} else {
return false;
}
#elif defined(USE_GCC_ATOMICS)
return __atomic_compare_exchange_n (at, &compareval, newval, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
#elif USE_TBB
atomic<long long> *a = (atomic<long long> *)at;
return a->compare_and_swap (newval, compareval) == newval;
#elif defined(_MSC_VER)
return (_InterlockedCompareExchange64 ((volatile LONGLONG *)at, newval, compareval) == compareval);
#else
# error No atomics on this platform.
#endif
}
/// Yield the processor for the rest of the timeslice.
///
inline void
yield ()
{
#if defined(__GNUC__)
sched_yield ();
#elif defined(_MSC_VER)
SwitchToThread ();
#else
# error No yield on this platform.
#endif
}
// Slight pause
inline void
pause (int delay)
{
#if defined(__GNUC__) && (defined(__x86_64__) || defined(__i386__))
for (int i = 0; i < delay; ++i)
__asm__ __volatile__("pause;");
#elif defined(__GNUC__) && (defined(__arm__) || defined(__s390__))
for (int i = 0; i < delay; ++i)
__asm__ __volatile__("NOP;");
#elif USE_TBB
__TBB_Pause(delay);
#elif defined(_MSC_VER)
for (int i = 0; i < delay; ++i) {
#if defined (_WIN64)
YieldProcessor();
#else
_asm pause
#endif /* _WIN64 */
}
#else
// No pause on this platform, just punt
for (int i = 0; i < delay; ++i) ;
#endif
}
// Helper class to deliver ever longer pauses until we yield our timeslice.
class atomic_backoff {
public:
atomic_backoff () : m_count(1) { }
void operator() () {
if (m_count <= 16) {
pause (m_count);
m_count *= 2;
} else {
yield();
}
}
private:
int m_count;
};
#if USE_TBB_ATOMIC
using tbb::atomic;
#else
// If we're not using TBB's atomic, we need to define our own atomic<>.
/// Atomic integer. Increment, decrement, add, and subtract in a
/// totally thread-safe manner.
template<class T>
class atomic {
public:
/// Construct with initial value.
///
atomic (T val=0) : m_val(val) { }
~atomic () { }
/// Retrieve value
///
T operator() () const { return atomic_exchange_and_add (&m_val, 0); }
/// Retrieve value
///
operator T() const { return atomic_exchange_and_add (&m_val, 0); }
/// Fast retrieval of value, no interchange, don't care about memory
/// fences.
T fast_value () const { return m_val; }
/// Assign new value.
///
T operator= (T x) {
//incorrect? return (m_val = x);
while (1) {
T result = m_val;
if (atomic_compare_and_exchange (&m_val, result, x))
break;
}
return x;
}
/// Pre-increment: ++foo
///
T operator++ () { return atomic_exchange_and_add (&m_val, 1) + 1; }
/// Post-increment: foo++
///
T operator++ (int) { return atomic_exchange_and_add (&m_val, 1); }
/// Pre-decrement: --foo
///
T operator-- () { return atomic_exchange_and_add (&m_val, -1) - 1; }
/// Post-decrement: foo--
///
T operator-- (int) { return atomic_exchange_and_add (&m_val, -1); }
/// Add to the value, return the new result
///
T operator+= (T x) { return atomic_exchange_and_add (&m_val, x) + x; }
/// Subtract from the value, return the new result
///
T operator-= (T x) { return atomic_exchange_and_add (&m_val, -x) - x; }
bool bool_compare_and_swap (T compareval, T newval) {
return atomic_compare_and_exchange (&m_val, compareval, newval);
}
T operator= (const atomic &x) {
T r = x();
*this = r;
return r;
}
private:
#ifdef __arm__
OIIO_ALIGN(8)
#endif
volatile mutable T m_val;
// Disallow copy construction by making private and unimplemented.
atomic (atomic const &);
};
#endif /* ! USE_TBB_ATOMIC */
#ifdef NOTHREADS
typedef int atomic_int;
typedef long long atomic_ll;
#else
typedef atomic<int> atomic_int;
typedef atomic<long long> atomic_ll;
#endif
#ifdef NOTHREADS
typedef null_mutex spin_mutex;
typedef null_lock<spin_mutex> spin_lock;
#elif USE_TBB_SPINLOCK
// Use TBB's spin locks
typedef tbb::spin_mutex spin_mutex;
typedef tbb::spin_mutex::scoped_lock spin_lock;
#else
// Define our own spin locks. Do we trust them?
/// A spin_mutex is semantically equivalent to a regular mutex, except
/// for the following:
/// - A spin_mutex is just 4 bytes, whereas a regular mutex is quite
/// large (44 bytes for pthread).
/// - A spin_mutex is extremely fast to lock and unlock, whereas a regular
/// mutex is surprisingly expensive just to acquire a lock.
/// - A spin_mutex takes CPU while it waits, so this can be very
/// wasteful compared to a regular mutex that blocks (gives up its
/// CPU slices until it acquires the lock).
///
/// The bottom line is that mutex is the usual choice, but in cases where
/// you need to acquire locks very frequently, but only need to hold the
/// lock for a very short period of time, you may save runtime by using
/// a spin_mutex, even though it's non-blocking.
///
/// N.B. A spin_mutex is only the size of an int. To avoid "false
/// sharing", be careful not to put two spin_mutex objects on the same
/// cache line (within 128 bytes of each other), or the two mutexes may
/// effectively (and wastefully) lock against each other.
///
class spin_mutex {
public:
/// Default constructor -- initialize to unlocked.
///
spin_mutex (void) { m_locked = 0; }
~spin_mutex (void) { }
/// Copy constructor -- initialize to unlocked.
///
spin_mutex (const spin_mutex &) { m_locked = 0; }
/// Assignment does not do anything, since lockedness should not
/// transfer.
const spin_mutex& operator= (const spin_mutex&) { return *this; }
/// Acquire the lock, spin until we have it.
///
void lock () {
// To avoid spinning too tightly, we use the atomic_backoff to
// provide increasingly longer pauses, and if the lock is under
// lots of contention, eventually yield the timeslice.
atomic_backoff backoff;
// Try to get ownership of the lock. Though experimentation, we
// found that OIIO_UNLIKELY makes this just a bit faster on
// gcc x86/x86_64 systems.
while (! OIIO_UNLIKELY(try_lock())) {
do {
backoff();
} while (m_locked);
// The full try_lock() involves a compare_and_swap, which
// writes memory, and that will lock the bus. But a normal
// read of m_locked will let us spin until the value
// changes, without locking the bus. So it's faster to
// check in this manner until the mutex appears to be free.
}
}
/// Release the lock that we hold.
///
void unlock () {
#if defined(__GNUC__) && (defined(__x86_64__) || defined(__i386__))
// Fastest way to do it is with a store with "release" semantics
__asm__ __volatile__("": : :"memory");
m_locked = 0;
// N.B. GCC gives us an intrinsic that is even better, an atomic
// assignment of 0 with "release" barrier semantics:
// __sync_lock_release (&m_locked);
// But empirically we found it not as performant as the above.
#elif defined(_MSC_VER)
_ReadWriteBarrier();
m_locked = 0;
#else
// Otherwise, just assign zero to the atomic (but that's a full
// memory barrier).
*(atomic_int *)&m_locked = 0;
#endif
}
/// Try to acquire the lock. Return true if we have it, false if
/// somebody else is holding the lock.
bool try_lock () {
#if USE_TBB_ATOMIC
// TBB's compare_and_swap returns the original value
return (*(atomic_int *)&m_locked).compare_and_swap (0, 1) == 0;
#elif defined(__GNUC__)
// GCC gives us an intrinsic that is even better -- an atomic
// exchange with "acquire" barrier semantics.
return __sync_lock_test_and_set (&m_locked, 1) == 0;
#else
// Our compare_and_swap returns true if it swapped
return atomic_compare_and_exchange (&m_locked, 0, 1);
#endif
}
/// Helper class: scoped lock for a spin_mutex -- grabs the lock upon
/// construction, releases the lock when it exits scope.
class lock_guard {
public:
lock_guard (spin_mutex &fm) : m_fm(fm) { m_fm.lock(); }
~lock_guard () { m_fm.unlock(); }
private:
lock_guard(); // Do not implement (even though TBB does)
lock_guard(const lock_guard& other); // Do not implement
lock_guard& operator = (const lock_guard& other); // Do not implement
spin_mutex & m_fm;
};
private:
volatile int m_locked; ///< Atomic counter is zero if nobody holds the lock
};
typedef spin_mutex::lock_guard spin_lock;
#endif
/// Spinning reader/writer mutex. This is just like spin_mutex, except
/// that there are separate locking mechanisms for "writers" (exclusive
/// holders of the lock, presumably because they are modifying whatever
/// the lock is protecting) and "readers" (non-exclusive, non-modifying
/// tasks that may access the protectee simultaneously).
class spin_rw_mutex {
public:
/// Default constructor -- initialize to unlocked.
///
spin_rw_mutex (void) { m_readers = 0; }
~spin_rw_mutex (void) { }
/// Copy constructor -- initialize to unlocked.
///
spin_rw_mutex (const spin_rw_mutex &) { m_readers = 0; }
/// Assignment does not do anything, since lockedness should not
/// transfer.
const spin_rw_mutex& operator= (const spin_rw_mutex&) { return *this; }
/// Acquire the reader lock.
///
void read_lock () {
// Spin until there are no writers active
m_locked.lock();
// Register ourself as a reader
++m_readers;
// Release the lock, to let other readers work
m_locked.unlock();
}
/// Release the reader lock.
///
void read_unlock () {
--m_readers; // it's atomic, no need to lock to release
}
/// Acquire the writer lock.
///
void write_lock () {
// Make sure no new readers (or writers) can start
m_locked.lock();
// Spin until the last reader is done, at which point we will be
// the sole owners and nobody else (reader or writer) can acquire
// the resource until we release it.
while (*(volatile int *)&m_readers > 0)
;
}
/// Release the writer lock.
///
void write_unlock () {
// Let other readers or writers get the lock
m_locked.unlock ();
}
/// Helper class: scoped read lock for a spin_rw_mutex -- grabs the
/// read lock upon construction, releases the lock when it exits scope.
class read_lock_guard {
public:
read_lock_guard (spin_rw_mutex &fm) : m_fm(fm) { m_fm.read_lock(); }
~read_lock_guard () { m_fm.read_unlock(); }
private:
read_lock_guard(); // Do not implement
read_lock_guard(const read_lock_guard& other); // Do not implement
read_lock_guard& operator = (const read_lock_guard& other); // Do not implement
spin_rw_mutex & m_fm;
};
/// Helper class: scoped write lock for a spin_rw_mutex -- grabs the
/// read lock upon construction, releases the lock when it exits scope.
class write_lock_guard {
public:
write_lock_guard (spin_rw_mutex &fm) : m_fm(fm) { m_fm.write_lock(); }
~write_lock_guard () { m_fm.write_unlock(); }
private:
write_lock_guard(); // Do not implement
write_lock_guard(const write_lock_guard& other); // Do not implement
write_lock_guard& operator = (const write_lock_guard& other); // Do not implement
spin_rw_mutex & m_fm;
};
private:
OIIO_CACHE_ALIGN
spin_mutex m_locked; // write lock
char pad1_[OIIO_CACHE_LINE_SIZE-sizeof(spin_mutex)];
OIIO_CACHE_ALIGN
atomic_int m_readers; // number of readers
char pad2_[OIIO_CACHE_LINE_SIZE-sizeof(atomic_int)];
};
typedef spin_rw_mutex::read_lock_guard spin_rw_read_lock;
typedef spin_rw_mutex::write_lock_guard spin_rw_write_lock;
}
OIIO_NAMESPACE_EXIT
#endif // OPENIMAGEIO_THREAD_H
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