tls.h

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/* -*- mode:C++; c-basic-offset:4 -*-
     Shore-MT -- Multi-threaded port of the SHORE storage manager
   
                       Copyright (c) 2007-2009
      Data Intensive Applications and Systems Labaratory (DIAS)
               Ecole Polytechnique Federale de Lausanne
   
                         All Rights Reserved.
   
   Permission to use, copy, modify and distribute this software and
   its documentation is hereby granted, provided that both the
   copyright notice and this permission notice appear in all copies of
   the software, derivative works or modified versions, and any
   portions thereof, and that both notices appear in supporting
   documentation.
   
   This code is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. THE AUTHORS
   DISCLAIM ANY LIABILITY OF ANY KIND FOR ANY DAMAGES WHATSOEVER
   RESULTING FROM THE USE OF THIS SOFTWARE.
*/

// -*- mode:c++; c-basic-offset:4 -*-
/*<std-header orig-src='shore' incl-file-exclusion='TLS_H'>

 $Id: tls.h,v 1.3 2010/06/23 23:42:57 nhall Exp $

SHORE -- Scalable Heterogeneous Object REpository

Copyright (c) 1994-99 Computer Sciences Department, University of
                      Wisconsin -- Madison
All Rights Reserved.

Permission to use, copy, modify and distribute this software and its
documentation is hereby granted, provided that both the copyright
notice and this permission notice appear in all copies of the
software, derivative works or modified versions, and any portions
thereof, and that both notices appear in supporting documentation.

THE AUTHORS AND THE COMPUTER SCIENCES DEPARTMENT OF THE UNIVERSITY
OF WISCONSIN - MADISON ALLOW FREE USE OF THIS SOFTWARE IN ITS
"AS IS" CONDITION, AND THEY DISCLAIM ANY LIABILITY OF ANY KIND
FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.

This software was developed with support by the Advanced Research
Project Agency, ARPA order number 018 (formerly 8230), monitored by
the U.S. Army Research Laboratory under contract DAAB07-91-C-Q518.
Further funding for this work was provided by DARPA through
Rome Research Laboratory Contract No. F30602-97-2-0247.

*/
#ifndef __TLS_H
#define __TLS_H

#include <pthread.h>
#include <new>

namespace tls_tricks {

    class tls_manager {
    public:
        static void global_init();

        static void global_fini();

        static void register_tls(void (* init)(), void (* fini)());

        static void thread_init();

        static void thread_fini();

        static __thread bool _thread_initialized;
    };

    struct tls_manager_schwarz {
        tls_manager_schwarz() {
            tls_manager::global_init();
        }

        ~tls_manager_schwarz() {
            tls_manager::global_fini();
        }
    };

    static struct tls_manager_schwarz tlsm_schwarz_one_and_only;

    template<typename T>
    struct tls_blob {
        enum {
            MAX_BYTES_NEEDED = sizeof(T) + sizeof(long) - 1,
            ARRAY_SIZE = MAX_BYTES_NEEDED / sizeof(long)
        };

        // force proper alignment...
        long _reserved_space[ARRAY_SIZE];

        void init() {
            new(get()) T;
        }

        void fini() {
            get()->~T();
        }

        T* get() {
            union {
                long* a;
                T* t;
            } u = {_reserved_space};
            return u.t;
        }
    };

/* WARNING: These thread-local variables essentially use the namespace
   of types, not variables for the purposes of detecting naming
   collisions. So, just as the following two declarations could lead
   to serious and hard-to-identify bugs: 

   -- file1.cpp --
   struct foo {
       int a; int b;
   };
   -- file2.cpp --
   
   struct foo {
    double a; char* b;
   };

   So, too, would the following:
   
   -- file1.cpp -- 
   DECLARE_TLS(foo, my_tls);
   -- file2.cpp --
   DECLARE_TLS(bar, my_tls);

   If you are lucky and the two types have different names the
   compiler may notice, otherwise you're on your own.
*/

#define TLS_STRUCT(Type, Name, InitFn)                    \
struct Name {                                            \
    typedef tls_tricks::tls_blob< Type > Wrapper;                \
    Type &operator*() { return *get(); }                \
    Type* operator->() { return get(); }                \
    operator Type*() { return get(); }                \
    static Wrapper* get_wrapper() {                    \
        static __thread Wrapper val;                \
        return &val;                        \
    }                                \
    static Type* get() { return get_wrapper()->get(); }        \
    static void init() { get_wrapper()->init(); }            \
    static void fini() { get_wrapper()->fini(); }            \
    InitFn() {                            \
        static bool initialized = false;                \
        if(initialized)                        \
        return;                            \
        tls_tricks::tls_manager::register_tls(&init, &fini);            \
        initialized = true;                        \
    }                                \
}


#define DECLARE_TLS(Type, Name) \
    static \
    TLS_STRUCT(Type, Name##_tls_wrapper, Name##_tls_wrapper) Name


#define DECLARE_TLS_SCHWARZ(Name)        \
    static struct Name##_tls_wrapper_schwarz {    \
            Name##_tls_wrapper_schwarz();        \
    } Name##_schwarz

#define DEFINE_TLS_SCHWARZ(Type, Name)                    \
    static TLS_STRUCT(Type, Name##_tls_wrapper, static void init_wrapper) Name; \
    Name##_tls_wrapper_schwarz::Name##_tls_wrapper_schwarz() {        \
        Name##_tls_wrapper::init_wrapper();                \
    }
} /* namespace tls_tricks */

#endif // __TLS_H