semaphore.h

Go to the documentation of this file.

/*
    Copyright (c) 2005-2018 Intel Corporation

    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at

        http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.




*/

#ifndef __TBB_tbb_semaphore_H
#define __TBB_tbb_semaphore_H

#include "tbb/tbb_stddef.h"

#if _WIN32||_WIN64
#include "tbb/machine/windows_api.h"

#elif __APPLE__
#include <mach/semaphore.h>
#include <mach/task.h>
#include <mach/mach_init.h>
#include <mach/error.h>

#else
#include <semaphore.h>
#ifdef TBB_USE_DEBUG
#include <errno.h>
#endif
#endif /*_WIN32||_WIN64*/

namespace tbb {
namespace internal {


#if _WIN32||_WIN64
typedef LONG sem_count_t;
class semaphore : no_copy {
    static const int max_semaphore_cnt = MAXLONG;
public:
    semaphore(size_t start_cnt_ = 0) {init_semaphore(start_cnt_);}
    ~semaphore() {CloseHandle( sem );}
    void P() {WaitForSingleObjectEx( sem, INFINITE, FALSE );}
    void V() {ReleaseSemaphore( sem, 1, NULL );}
private:
    HANDLE sem;
    void init_semaphore(size_t start_cnt_) {
        sem = CreateSemaphoreEx( NULL, LONG(start_cnt_), max_semaphore_cnt, NULL, 0, SEMAPHORE_ALL_ACCESS );
    }
};
#elif __APPLE__
class semaphore : no_copy {
public:
    semaphore(int start_cnt_ = 0) : sem(start_cnt_) { init_semaphore(start_cnt_); }
    ~semaphore() {
        kern_return_t ret = semaphore_destroy( mach_task_self(), sem );
        __TBB_ASSERT_EX( ret==err_none, NULL );
    }
    void P() {
        int ret;
        do {
            ret = semaphore_wait( sem );
        } while( ret==KERN_ABORTED );
        __TBB_ASSERT( ret==KERN_SUCCESS, "semaphore_wait() failed" );
    }
    void V() { semaphore_signal( sem ); }
private:
    semaphore_t sem;
    void init_semaphore(int start_cnt_) {
        kern_return_t ret = semaphore_create( mach_task_self(), &sem, SYNC_POLICY_FIFO, start_cnt_ );
        __TBB_ASSERT_EX( ret==err_none, "failed to create a semaphore" );
    }
};
#else /* Linux/Unix */
typedef uint32_t sem_count_t;
class semaphore : no_copy {
public:
    semaphore(int start_cnt_ = 0 ) { init_semaphore( start_cnt_ ); }

    ~semaphore() {
        int ret = sem_destroy( &sem );
        __TBB_ASSERT_EX( !ret, NULL );
    }
    void P() {
        while( sem_wait( &sem )!=0 )
            __TBB_ASSERT( errno==EINTR, NULL );
    }
    void V() { sem_post( &sem ); }
private:
    sem_t sem;
    void init_semaphore(int start_cnt_) {
        int ret = sem_init( &sem, /*shared among threads*/ 0, start_cnt_ );
        __TBB_ASSERT_EX( !ret, NULL );
    }
};
#endif /* _WIN32||_WIN64 */


#if _WIN32||_WIN64
#if !__TBB_USE_SRWLOCK
class binary_semaphore : no_copy {
public:
    binary_semaphore() { my_sem = CreateEventEx( NULL, NULL, 0, EVENT_ALL_ACCESS );  }
    ~binary_semaphore() { CloseHandle( my_sem ); }
    void P() { WaitForSingleObjectEx( my_sem, INFINITE, FALSE ); }
    void V() { SetEvent( my_sem ); }
private:
    HANDLE my_sem;
};
#else /* __TBB_USE_SRWLOCK */

union srwl_or_handle {
    SRWLOCK lock;
    HANDLE  h;
};

class binary_semaphore : no_copy {
public:
    binary_semaphore();
    ~binary_semaphore();
    void P();
    void V();
private:
    srwl_or_handle my_sem;
};
#endif /* !__TBB_USE_SRWLOCK */
#elif __APPLE__
class binary_semaphore : no_copy {
public:
    binary_semaphore() : my_sem(0) {
        kern_return_t ret = semaphore_create( mach_task_self(), &my_sem, SYNC_POLICY_FIFO, 0 );
        __TBB_ASSERT_EX( ret==err_none, "failed to create a semaphore" );
    }
    ~binary_semaphore() {
        kern_return_t ret = semaphore_destroy( mach_task_self(), my_sem );
        __TBB_ASSERT_EX( ret==err_none, NULL );
    }
    void P() {
        int ret;
        do {
            ret = semaphore_wait( my_sem );
        } while( ret==KERN_ABORTED );
        __TBB_ASSERT( ret==KERN_SUCCESS, "semaphore_wait() failed" );
    }
    void V() { semaphore_signal( my_sem ); }
private:
    semaphore_t my_sem;
};
#else /* Linux/Unix */

#if __TBB_USE_FUTEX
class binary_semaphore : no_copy {
// The implementation is equivalent to the "Mutex, Take 3" one
// in the paper "Futexes Are Tricky" by Ulrich Drepper
public:
    binary_semaphore() { my_sem = 1; }
    ~binary_semaphore() {}
    void P() {
        int s;
        if( (s = my_sem.compare_and_swap( 1, 0 ))!=0 ) {
            if( s!=2 )
                s = my_sem.fetch_and_store( 2 );
            while( s!=0 ) { // This loop deals with spurious wakeup
                futex_wait( &my_sem, 2 );
                s = my_sem.fetch_and_store( 2 );
            }
        }
    }
    void V() {
        __TBB_ASSERT( my_sem>=1, "multiple V()'s in a row?" );
        if( my_sem.fetch_and_store( 0 )==2 )
            futex_wakeup_one( &my_sem );
    }
private:
    atomic<int> my_sem; // 0 - open; 1 - closed, no waits; 2 - closed, possible waits
};
#else
typedef uint32_t sem_count_t;
class binary_semaphore : no_copy {
public:
    binary_semaphore() {
        int ret = sem_init( &my_sem, /*shared among threads*/ 0, 0 );
        __TBB_ASSERT_EX( !ret, NULL );
    }
    ~binary_semaphore() {
        int ret = sem_destroy( &my_sem );
        __TBB_ASSERT_EX( !ret, NULL );
    }
    void P() {
        while( sem_wait( &my_sem )!=0 )
            __TBB_ASSERT( errno==EINTR, NULL );
    }
    void V() { sem_post( &my_sem ); }
private:
    sem_t my_sem;
};
#endif /* __TBB_USE_FUTEX */
#endif /* _WIN32||_WIN64 */

} // namespace internal
} // namespace tbb

#endif /* __TBB_tbb_semaphore_H */