task.h

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/*
    Copyright (c) 2005-2020 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.
*/

#include "internal/_deprecated_header_message_guard.h"

#if !defined(__TBB_show_deprecation_message_task_H) && defined(__TBB_show_deprecated_header_message)
#define  __TBB_show_deprecation_message_task_H
#pragma message("TBB Warning: tbb/task.h is deprecated. For details, please see Deprecated Features appendix in the TBB reference manual.")
#endif

#if defined(__TBB_show_deprecated_header_message)
#undef __TBB_show_deprecated_header_message
#endif

#ifndef __TBB_task_H
#define __TBB_task_H

#define __TBB_task_H_include_area
#include "internal/_warning_suppress_enable_notice.h"

#include "tbb_stddef.h"
#include "tbb_machine.h"
#include "tbb_profiling.h"
#include <climits>

typedef struct ___itt_caller *__itt_caller;

namespace tbb {

class task;
class task_list;
class task_group_context;

// MSVC does not allow taking the address of a member that was defined
// privately in task_base and made public in class task via a using declaration.
#if _MSC_VER || (__GNUC__==3 && __GNUC_MINOR__<3)
#define __TBB_TASK_BASE_ACCESS public
#else
#define __TBB_TASK_BASE_ACCESS private
#endif

namespace internal { //< @cond INTERNAL

    class allocate_additional_child_of_proxy: no_assign {
        task* self;
        task& parent;
    public:
        explicit allocate_additional_child_of_proxy( task& parent_ ) : self(NULL), parent(parent_) {
            suppress_unused_warning( self );
        }
        task& __TBB_EXPORTED_METHOD allocate( size_t size ) const;
        void __TBB_EXPORTED_METHOD free( task& ) const;
    };

    struct cpu_ctl_env_space { int space[sizeof(internal::uint64_t)/sizeof(int)]; };
} //< namespace internal @endcond

namespace interface5 {
    namespace internal {

        class task_base: tbb::internal::no_copy {
        __TBB_TASK_BASE_ACCESS:
            friend class tbb::task;

            static void spawn( task& t );

            static void spawn( task_list& list );


            static tbb::internal::allocate_additional_child_of_proxy allocate_additional_child_of( task& t ) {
                return tbb::internal::allocate_additional_child_of_proxy(t);
            }


            static void __TBB_EXPORTED_FUNC destroy( task& victim );
        };
    } // internal
} // interface5

namespace internal {

    class scheduler: no_copy {
    public:
        virtual void spawn( task& first, task*& next ) = 0;

        virtual void wait_for_all( task& parent, task* child ) = 0;

        virtual void spawn_root_and_wait( task& first, task*& next ) = 0;

        //  Have to have it just to shut up overzealous compilation warnings
        virtual ~scheduler() = 0;

        virtual void enqueue( task& t, void* reserved ) = 0;
    };


    typedef intptr_t reference_count;

#if __TBB_PREVIEW_RESUMABLE_TASKS
    static const reference_count abandon_flag = reference_count(1) << (sizeof(reference_count)*CHAR_BIT - 2);
#endif

    typedef unsigned short affinity_id;

#if __TBB_TASK_ISOLATION
    typedef intptr_t isolation_tag;
    const isolation_tag no_isolation = 0;
#endif /* __TBB_TASK_ISOLATION */

#if __TBB_TASK_GROUP_CONTEXT
    class generic_scheduler;

    struct context_list_node_t {
        context_list_node_t *my_prev,
                            *my_next;
    };

    class allocate_root_with_context_proxy: no_assign {
        task_group_context& my_context;
    public:
        allocate_root_with_context_proxy ( task_group_context& ctx ) : my_context(ctx) {}
        task& __TBB_EXPORTED_METHOD allocate( size_t size ) const;
        void __TBB_EXPORTED_METHOD free( task& ) const;
    };
#endif /* __TBB_TASK_GROUP_CONTEXT */

    class allocate_root_proxy: no_assign {
    public:
        static task& __TBB_EXPORTED_FUNC allocate( size_t size );
        static void __TBB_EXPORTED_FUNC free( task& );
    };

    class allocate_continuation_proxy: no_assign {
    public:
        task& __TBB_EXPORTED_METHOD allocate( size_t size ) const;
        void __TBB_EXPORTED_METHOD free( task& ) const;
    };

    class allocate_child_proxy: no_assign {
    public:
        task& __TBB_EXPORTED_METHOD allocate( size_t size ) const;
        void __TBB_EXPORTED_METHOD free( task& ) const;
    };

#if __TBB_PREVIEW_CRITICAL_TASKS
    // TODO: move to class methods when critical task API becomes public
    void make_critical( task& t );
    bool is_critical( task& t );
#endif


    class task_prefix {
    private:
        friend class tbb::task;
        friend class tbb::interface5::internal::task_base;
        friend class tbb::task_list;
        friend class internal::scheduler;
        friend class internal::allocate_root_proxy;
        friend class internal::allocate_child_proxy;
        friend class internal::allocate_continuation_proxy;
        friend class internal::allocate_additional_child_of_proxy;
#if __TBB_PREVIEW_CRITICAL_TASKS
        friend void make_critical( task& );
        friend bool is_critical( task& );
#endif

#if __TBB_TASK_ISOLATION
        isolation_tag isolation;
#else
        intptr_t reserved_space_for_task_isolation_tag;
#endif /* __TBB_TASK_ISOLATION */

#if __TBB_TASK_GROUP_CONTEXT

        task_group_context  *context;
#endif /* __TBB_TASK_GROUP_CONTEXT */


        scheduler* origin;

#if __TBB_TASK_PRIORITY || __TBB_PREVIEW_RESUMABLE_TASKS
        union {
#endif /* __TBB_TASK_PRIORITY */

        scheduler* owner;

#if __TBB_TASK_PRIORITY

        task* next_offloaded;
#endif

#if __TBB_PREVIEW_RESUMABLE_TASKS
        scheduler* abandoned_scheduler;
#endif
#if __TBB_TASK_PRIORITY || __TBB_PREVIEW_RESUMABLE_TASKS
        };
#endif /* __TBB_TASK_PRIORITY || __TBB_PREVIEW_RESUMABLE_TASKS */


        tbb::task* parent;


        __TBB_atomic reference_count ref_count;


        int depth;


        unsigned char state;


        unsigned char extra_state;

        affinity_id affinity;

        tbb::task* next;

        tbb::task& task() {return *reinterpret_cast<tbb::task*>(this+1);}
    };

} // namespace internal

#if __TBB_TASK_GROUP_CONTEXT

#if __TBB_TASK_PRIORITY
namespace internal {
    static const int priority_stride_v4 = INT_MAX / 4;
#if __TBB_PREVIEW_CRITICAL_TASKS
    // TODO: move into priority_t enum when critical tasks become public feature
    static const int priority_critical = priority_stride_v4 * 3 + priority_stride_v4 / 3 * 2;
#endif
}

enum priority_t {
    priority_normal = internal::priority_stride_v4 * 2,
    priority_low = priority_normal - internal::priority_stride_v4,
    priority_high = priority_normal + internal::priority_stride_v4
};

#endif /* __TBB_TASK_PRIORITY */

#if TBB_USE_CAPTURED_EXCEPTION
    class tbb_exception;
#else
    namespace internal {
        class tbb_exception_ptr;
    }
#endif /* !TBB_USE_CAPTURED_EXCEPTION */

class task_scheduler_init;
namespace interface7 { class task_arena; }
using interface7::task_arena;


class task_group_context : internal::no_copy {
private:
    friend class internal::generic_scheduler;
    friend class task_scheduler_init;
    friend class task_arena;

#if TBB_USE_CAPTURED_EXCEPTION
    typedef tbb_exception exception_container_type;
#else
    typedef internal::tbb_exception_ptr exception_container_type;
#endif

    enum version_traits_word_layout {
        traits_offset = 16,
        version_mask = 0xFFFF,
        traits_mask = 0xFFFFul << traits_offset
    };

public:
    enum kind_type {
        isolated,
        bound
    };

    enum traits_type {
        exact_exception = 0x0001ul << traits_offset,
#if __TBB_FP_CONTEXT
        fp_settings     = 0x0002ul << traits_offset,
#endif
        concurrent_wait = 0x0004ul << traits_offset,
#if TBB_USE_CAPTURED_EXCEPTION
        default_traits = 0
#else
        default_traits = exact_exception
#endif /* !TBB_USE_CAPTURED_EXCEPTION */
    };

private:
    enum state {
        may_have_children = 1,
        // the following enumerations must be the last, new 2^x values must go above
        next_state_value, low_unused_state_bit = (next_state_value-1)*2
    };

    union {
        // TODO: describe asynchronous use, and whether any memory semantics are needed
        __TBB_atomic kind_type my_kind;
        uintptr_t _my_kind_aligner;
    };

    task_group_context *my_parent;


    internal::context_list_node_t my_node;

    __itt_caller itt_caller;


    char _leading_padding[internal::NFS_MaxLineSize
                          - 2 * sizeof(uintptr_t)- sizeof(void*) - sizeof(internal::context_list_node_t)
                          - sizeof(__itt_caller)
#if __TBB_FP_CONTEXT
                          - sizeof(internal::cpu_ctl_env_space)
#endif
                         ];

#if __TBB_FP_CONTEXT

    internal::cpu_ctl_env_space my_cpu_ctl_env;
#endif

    uintptr_t my_cancellation_requested;


    uintptr_t my_version_and_traits;

    exception_container_type *my_exception;

    internal::generic_scheduler *my_owner;

    uintptr_t my_state;

#if __TBB_TASK_PRIORITY
    intptr_t my_priority;
#endif /* __TBB_TASK_PRIORITY */

    internal::string_index my_name;


    char _trailing_padding[internal::NFS_MaxLineSize - 2 * sizeof(uintptr_t) - 2 * sizeof(void*)
#if __TBB_TASK_PRIORITY
                           - sizeof(intptr_t)
#endif /* __TBB_TASK_PRIORITY */
                           - sizeof(internal::string_index)
                          ];

public:

    task_group_context ( kind_type relation_with_parent = bound,
                         uintptr_t t = default_traits )
        : my_kind(relation_with_parent)
        , my_version_and_traits(3 | t)
        , my_name(internal::CUSTOM_CTX)
    {
        init();
    }

    // Custom constructor for instrumentation of tbb algorithm
    task_group_context ( internal::string_index name )
        : my_kind(bound)
        , my_version_and_traits(3 | default_traits)
        , my_name(name)
    {
        init();
    }

    // Do not introduce standalone unbind method since it will break state propagation assumptions
    __TBB_EXPORTED_METHOD ~task_group_context ();


    void __TBB_EXPORTED_METHOD reset ();


    bool __TBB_EXPORTED_METHOD cancel_group_execution ();

    bool __TBB_EXPORTED_METHOD is_group_execution_cancelled () const;


    void __TBB_EXPORTED_METHOD register_pending_exception ();

#if __TBB_FP_CONTEXT

    void __TBB_EXPORTED_METHOD capture_fp_settings ();
#endif

#if __TBB_TASK_PRIORITY
    __TBB_DEPRECATED_IN_VERBOSE_MODE void set_priority ( priority_t );

    __TBB_DEPRECATED_IN_VERBOSE_MODE priority_t priority () const;
#endif /* __TBB_TASK_PRIORITY */

    uintptr_t traits() const { return my_version_and_traits & traits_mask; }

protected:

    void __TBB_EXPORTED_METHOD init ();

private:
    friend class task;
    friend class internal::allocate_root_with_context_proxy;

    static const kind_type binding_required = bound;
    static const kind_type binding_completed = kind_type(bound+1);
    static const kind_type detached = kind_type(binding_completed+1);
    static const kind_type dying = kind_type(detached+1);

    template <typename T>
    void propagate_task_group_state ( T task_group_context::*mptr_state, task_group_context& src, T new_state );

    void bind_to ( internal::generic_scheduler *local_sched );

    void register_with ( internal::generic_scheduler *local_sched );

#if __TBB_FP_CONTEXT
    // TODO: Consider adding #else stub in order to omit #if sections in other code
    void copy_fp_settings( const task_group_context &src );
#endif /* __TBB_FP_CONTEXT */
}; // class task_group_context

#endif /* __TBB_TASK_GROUP_CONTEXT */


class __TBB_DEPRECATED_IN_VERBOSE_MODE task: __TBB_TASK_BASE_ACCESS interface5::internal::task_base {

    void __TBB_EXPORTED_METHOD internal_set_ref_count( int count );

    internal::reference_count __TBB_EXPORTED_METHOD internal_decrement_ref_count();

protected:
    task() {prefix().extra_state=1;}

public:
    virtual ~task() {}

    virtual task* execute() = 0;

    enum state_type {
        executing,
        reexecute,
        ready,
        allocated,
        freed,
        recycle
#if __TBB_RECYCLE_TO_ENQUEUE
        ,to_enqueue
#endif
#if __TBB_PREVIEW_RESUMABLE_TASKS
        ,to_resume
#endif
    };

    //------------------------------------------------------------------------
    // Allocating tasks
    //------------------------------------------------------------------------

    static internal::allocate_root_proxy allocate_root() {
        return internal::allocate_root_proxy();
    }

#if __TBB_TASK_GROUP_CONTEXT
    static internal::allocate_root_with_context_proxy allocate_root( task_group_context& ctx ) {
        return internal::allocate_root_with_context_proxy(ctx);
    }
#endif /* __TBB_TASK_GROUP_CONTEXT */


    internal::allocate_continuation_proxy& allocate_continuation() {
        return *reinterpret_cast<internal::allocate_continuation_proxy*>(this);
    }

    internal::allocate_child_proxy& allocate_child() {
        return *reinterpret_cast<internal::allocate_child_proxy*>(this);
    }

    using task_base::allocate_additional_child_of;

#if __TBB_DEPRECATED_TASK_INTERFACE

    void __TBB_EXPORTED_METHOD destroy( task& t );
#else /* !__TBB_DEPRECATED_TASK_INTERFACE */
    using task_base::destroy;
#endif /* !__TBB_DEPRECATED_TASK_INTERFACE */

    //------------------------------------------------------------------------
    // Recycling of tasks
    //------------------------------------------------------------------------


    void recycle_as_continuation() {
        __TBB_ASSERT( prefix().state==executing, "execute not running?" );
        prefix().state = allocated;
    }


    void recycle_as_safe_continuation() {
        __TBB_ASSERT( prefix().state==executing, "execute not running?" );
        prefix().state = recycle;
    }

    void recycle_as_child_of( task& new_parent ) {
        internal::task_prefix& p = prefix();
        __TBB_ASSERT( prefix().state==executing||prefix().state==allocated, "execute not running, or already recycled" );
        __TBB_ASSERT( prefix().ref_count==0, "no child tasks allowed when recycled as a child" );
        __TBB_ASSERT( p.parent==NULL, "parent must be null" );
        __TBB_ASSERT( new_parent.prefix().state<=recycle, "corrupt parent's state" );
        __TBB_ASSERT( new_parent.prefix().state!=freed, "parent already freed" );
        p.state = allocated;
        p.parent = &new_parent;
#if __TBB_TASK_GROUP_CONTEXT
        p.context = new_parent.prefix().context;
#endif /* __TBB_TASK_GROUP_CONTEXT */
    }


    void recycle_to_reexecute() {
        __TBB_ASSERT( prefix().state==executing, "execute not running, or already recycled" );
        __TBB_ASSERT( prefix().ref_count==0, "no child tasks allowed when recycled for reexecution" );
        prefix().state = reexecute;
    }

#if __TBB_RECYCLE_TO_ENQUEUE

    void recycle_to_enqueue() {
        __TBB_ASSERT( prefix().state==executing, "execute not running, or already recycled" );
        prefix().state = to_enqueue;
    }
#endif /* __TBB_RECYCLE_TO_ENQUEUE */

    //------------------------------------------------------------------------
    // Spawning and blocking
    //------------------------------------------------------------------------

    void set_ref_count( int count ) {
#if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT
        internal_set_ref_count(count);
#else
        prefix().ref_count = count;
#endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT */
    }


    void increment_ref_count() {
        __TBB_FetchAndIncrementWacquire( &prefix().ref_count );
    }


    int add_ref_count( int count ) {
        internal::call_itt_notify( internal::releasing, &prefix().ref_count );
        internal::reference_count k = count+__TBB_FetchAndAddW( &prefix().ref_count, count );
        __TBB_ASSERT( k>=0, "task's reference count underflowed" );
        if( k==0 )
            internal::call_itt_notify( internal::acquired, &prefix().ref_count );
        return int(k);
    }


    int decrement_ref_count() {
#if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT
        return int(internal_decrement_ref_count());
#else
        return int(__TBB_FetchAndDecrementWrelease( &prefix().ref_count ))-1;
#endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT */
    }

    using task_base::spawn;

    void spawn_and_wait_for_all( task& child ) {
        prefix().owner->wait_for_all( *this, &child );
    }

    void __TBB_EXPORTED_METHOD spawn_and_wait_for_all( task_list& list );

    static void spawn_root_and_wait( task& root ) {
        root.prefix().owner->spawn_root_and_wait( root, root.prefix().next );
    }


    static void spawn_root_and_wait( task_list& root_list );


    void wait_for_all() {
        prefix().owner->wait_for_all( *this, NULL );
    }

#if __TBB_TASK_PRIORITY

#endif /* __TBB_TASK_PRIORITY */
    static void enqueue( task& t ) {
        t.prefix().owner->enqueue( t, NULL );
    }

#if __TBB_TASK_PRIORITY
    static void enqueue( task& t, priority_t p ) {
#if __TBB_PREVIEW_CRITICAL_TASKS
        __TBB_ASSERT(p == priority_low || p == priority_normal || p == priority_high
                     || p == internal::priority_critical, "Invalid priority level value");
#else
        __TBB_ASSERT(p == priority_low || p == priority_normal || p == priority_high, "Invalid priority level value");
#endif
        t.prefix().owner->enqueue( t, (void*)p );
    }
#endif /* __TBB_TASK_PRIORITY */

#if __TBB_TASK_PRIORITY
    inline static void enqueue( task& t, task_arena& arena, priority_t p = priority_t(0) );
#else
    inline static void enqueue( task& t, task_arena& arena);
#endif

    static task& __TBB_EXPORTED_FUNC self();

    task* parent() const {return prefix().parent;}

    void set_parent(task* p) {
#if __TBB_TASK_GROUP_CONTEXT
        __TBB_ASSERT(!p || prefix().context == p->prefix().context, "The tasks must be in the same context");
#endif
        prefix().parent = p;
    }

#if __TBB_TASK_GROUP_CONTEXT

    task_group_context* context() {return prefix().context;}

    task_group_context* group () { return prefix().context; }
#endif /* __TBB_TASK_GROUP_CONTEXT */

    bool is_stolen_task() const {
        return (prefix().extra_state & 0x80)!=0;
    }

    bool is_enqueued_task() const {
        // es_task_enqueued = 0x10
        return (prefix().extra_state & 0x10)!=0;
    }

#if __TBB_PREVIEW_RESUMABLE_TASKS
    typedef void* suspend_point;

    template <typename F>
    static void suspend(F f);

    static void resume(suspend_point tag);
#endif

    //------------------------------------------------------------------------
    // Debugging
    //------------------------------------------------------------------------

    state_type state() const {return state_type(prefix().state);}

    int ref_count() const {
#if TBB_USE_ASSERT
#if __TBB_PREVIEW_RESUMABLE_TASKS
        internal::reference_count ref_count_ = prefix().ref_count & ~internal::abandon_flag;
#else
        internal::reference_count ref_count_ = prefix().ref_count;
#endif
        __TBB_ASSERT( ref_count_==int(ref_count_), "integer overflow error");
#endif
#if __TBB_PREVIEW_RESUMABLE_TASKS
        return int(prefix().ref_count & ~internal::abandon_flag);
#else
        return int(prefix().ref_count);
#endif
    }

    bool __TBB_EXPORTED_METHOD is_owned_by_current_thread() const;

    //------------------------------------------------------------------------
    // Affinity
    //------------------------------------------------------------------------


    typedef internal::affinity_id affinity_id;

    void set_affinity( affinity_id id ) {prefix().affinity = id;}

    affinity_id affinity() const {return prefix().affinity;}


    virtual void __TBB_EXPORTED_METHOD note_affinity( affinity_id id );

#if __TBB_TASK_GROUP_CONTEXT

    void __TBB_EXPORTED_METHOD change_group ( task_group_context& ctx );


    bool cancel_group_execution () { return prefix().context->cancel_group_execution(); }

    bool is_cancelled () const { return prefix().context->is_group_execution_cancelled(); }
#else
    bool is_cancelled () const { return false; }
#endif /* __TBB_TASK_GROUP_CONTEXT */

#if __TBB_TASK_PRIORITY
    __TBB_DEPRECATED void set_group_priority ( priority_t p ) {  prefix().context->set_priority(p); }

    __TBB_DEPRECATED priority_t group_priority () const { return prefix().context->priority(); }

#endif /* __TBB_TASK_PRIORITY */

private:
    friend class interface5::internal::task_base;
    friend class task_list;
    friend class internal::scheduler;
    friend class internal::allocate_root_proxy;
#if __TBB_TASK_GROUP_CONTEXT
    friend class internal::allocate_root_with_context_proxy;
#endif /* __TBB_TASK_GROUP_CONTEXT */
    friend class internal::allocate_continuation_proxy;
    friend class internal::allocate_child_proxy;
    friend class internal::allocate_additional_child_of_proxy;


    internal::task_prefix& prefix( internal::version_tag* = NULL ) const {
        return reinterpret_cast<internal::task_prefix*>(const_cast<task*>(this))[-1];
    }
#if __TBB_PREVIEW_CRITICAL_TASKS
    friend void internal::make_critical( task& );
    friend bool internal::is_critical( task& );
#endif
}; // class task

#if __TBB_PREVIEW_CRITICAL_TASKS
namespace internal {
inline void make_critical( task& t ) { t.prefix().extra_state |= 0x8; }
inline bool is_critical( task& t ) { return bool((t.prefix().extra_state & 0x8) != 0); }
} // namespace internal
#endif /* __TBB_PREVIEW_CRITICAL_TASKS */

#if __TBB_PREVIEW_RESUMABLE_TASKS
namespace internal {
    template <typename F>
    static void suspend_callback(void* user_callback, task::suspend_point tag) {
        // Copy user function to a new stack to avoid a race when the previous scheduler is resumed.
        F user_callback_copy = *static_cast<F*>(user_callback);
        user_callback_copy(tag);
    }
    void __TBB_EXPORTED_FUNC internal_suspend(void* suspend_callback, void* user_callback);
    void __TBB_EXPORTED_FUNC internal_resume(task::suspend_point);
    task::suspend_point __TBB_EXPORTED_FUNC internal_current_suspend_point();
}

template <typename F>
inline void task::suspend(F f) {
    internal::internal_suspend((void*)internal::suspend_callback<F>, &f);
}
inline void task::resume(suspend_point tag) {
    internal::internal_resume(tag);
}
#endif


class __TBB_DEPRECATED_IN_VERBOSE_MODE empty_task: public task {
    task* execute() __TBB_override {
        return NULL;
    }
};

namespace internal {
    template<typename F>
    class function_task : public task {
#if __TBB_ALLOW_MUTABLE_FUNCTORS
        // TODO: deprecated behavior, remove
        F my_func;
#else
        const F my_func;
#endif
        task* execute() __TBB_override {
            my_func();
            return NULL;
        }
    public:
        function_task( const F& f ) : my_func(f) {}
#if __TBB_CPP11_RVALUE_REF_PRESENT
        function_task( F&& f ) : my_func( std::move(f) ) {}
#endif
    };
} // namespace internal


class __TBB_DEPRECATED_IN_VERBOSE_MODE task_list: internal::no_copy {
private:
    task* first;
    task** next_ptr;
    friend class task;
    friend class interface5::internal::task_base;
public:
    task_list() : first(NULL), next_ptr(&first) {}

    ~task_list() {}

    bool empty() const {return !first;}

    void push_back( task& task ) {
        task.prefix().next = NULL;
        *next_ptr = &task;
        next_ptr = &task.prefix().next;
    }
#if __TBB_TODO
    // TODO: add this method and implement&document the local execution ordering. See more in generic_scheduler::local_spawn
    void push_front( task& task ) {
        if( empty() ) {
            push_back(task);
        } else {
            task.prefix().next = first;
            first = &task;
        }
    }
#endif
    task& pop_front() {
        __TBB_ASSERT( !empty(), "attempt to pop item from empty task_list" );
        task* result = first;
        first = result->prefix().next;
        if( !first ) next_ptr = &first;
        return *result;
    }

    void clear() {
        first=NULL;
        next_ptr=&first;
    }
};

inline void interface5::internal::task_base::spawn( task& t ) {
    t.prefix().owner->spawn( t, t.prefix().next );
}

inline void interface5::internal::task_base::spawn( task_list& list ) {
    if( task* t = list.first ) {
        t->prefix().owner->spawn( *t, *list.next_ptr );
        list.clear();
    }
}

inline void task::spawn_root_and_wait( task_list& root_list ) {
    if( task* t = root_list.first ) {
        t->prefix().owner->spawn_root_and_wait( *t, *root_list.next_ptr );
        root_list.clear();
    }
}

} // namespace tbb

inline void *operator new( size_t bytes, const tbb::internal::allocate_root_proxy& ) {
    return &tbb::internal::allocate_root_proxy::allocate(bytes);
}

inline void operator delete( void* task, const tbb::internal::allocate_root_proxy& ) {
    tbb::internal::allocate_root_proxy::free( *static_cast<tbb::task*>(task) );
}

#if __TBB_TASK_GROUP_CONTEXT
inline void *operator new( size_t bytes, const tbb::internal::allocate_root_with_context_proxy& p ) {
    return &p.allocate(bytes);
}

inline void operator delete( void* task, const tbb::internal::allocate_root_with_context_proxy& p ) {
    p.free( *static_cast<tbb::task*>(task) );
}
#endif /* __TBB_TASK_GROUP_CONTEXT */

inline void *operator new( size_t bytes, const tbb::internal::allocate_continuation_proxy& p ) {
    return &p.allocate(bytes);
}

inline void operator delete( void* task, const tbb::internal::allocate_continuation_proxy& p ) {
    p.free( *static_cast<tbb::task*>(task) );
}

inline void *operator new( size_t bytes, const tbb::internal::allocate_child_proxy& p ) {
    return &p.allocate(bytes);
}

inline void operator delete( void* task, const tbb::internal::allocate_child_proxy& p ) {
    p.free( *static_cast<tbb::task*>(task) );
}

inline void *operator new( size_t bytes, const tbb::internal::allocate_additional_child_of_proxy& p ) {
    return &p.allocate(bytes);
}

inline void operator delete( void* task, const tbb::internal::allocate_additional_child_of_proxy& p ) {
    p.free( *static_cast<tbb::task*>(task) );
}

#include "internal/_warning_suppress_disable_notice.h"
#undef __TBB_task_H_include_area

#endif /* __TBB_task_H */