ceph/src/boost/boost/context/execution_context_v1.hpp

   1
   2 //          Copyright Oliver Kowalke 2014.
   3 // Distributed under the Boost Software License, Version 1.0.
   4 //    (See accompanying file LICENSE_1_0.txt or copy at
   5 //          http://www.boost.org/LICENSE_1_0.txt)
   6
   7 #ifndef BOOST_CONTEXT_EXECUTION_CONTEXT_V1_H
   8 #define BOOST_CONTEXT_EXECUTION_CONTEXT_V1_H
   9
  10 #include <boost/context/detail/config.hpp>
  11
  12 #include <algorithm>
  13 #include <atomic>
  14 #include <cstddef>
  15 #include <cstdint>
  16 #include <cstdlib>
  17 #include <functional>
  18 #include <memory>
  19 #include <ostream>
  20 #include <tuple>
  21 #include <utility>
  22
  23 #include <boost/assert.hpp>
  24 #include <boost/config.hpp>
  25 #include <boost/intrusive_ptr.hpp>
  26
  27 #if defined(BOOST_NO_CXX17_STD_APPLY)
  28 #include <boost/context/detail/apply.hpp>
  29 #endif
  30 #include <boost/context/detail/disable_overload.hpp>
  31 #include <boost/context/detail/externc.hpp>
  32 #include <boost/context/detail/fcontext.hpp>
  33 #include <boost/context/fixedsize_stack.hpp>
  34 #include <boost/context/flags.hpp>
  35 #include <boost/context/preallocated.hpp>
  36 #include <boost/context/segmented_stack.hpp>
  37 #include <boost/context/stack_context.hpp>
  38
  39 #ifdef BOOST_HAS_ABI_HEADERS
  40 # include BOOST_ABI_PREFIX
  41 #endif
  42
  43 namespace boost {
  44 namespace context {
  45 namespace detail {
  46
  47 template< typename Fn >
  48 transfer_t ecv1_context_ontop( transfer_t);
  49
  50 struct ecv1_activation_record;
  51
  52 struct ecv1_data_t {
  53     ecv1_activation_record  *   from;
  54     void                    *   data;
  55 };
  56
  57 struct BOOST_CONTEXT_DECL ecv1_activation_record {
  58     typedef boost::intrusive_ptr< ecv1_activation_record >    ptr_t;
  59
  60     static ptr_t & current() noexcept;
  61
  62     std::atomic< std::size_t >  use_count{ 0 };
  63     fcontext_t                  fctx{ nullptr };
  64     stack_context               sctx{};
  65     bool                        main_ctx{ true };
  66
  67     // used for toplevel-context
  68     // (e.g. main context, thread-entry context)
  69     ecv1_activation_record() = default;
  70
  71     ecv1_activation_record( fcontext_t fctx_, stack_context sctx_) noexcept :
  72         fctx{ fctx_ },
  73         sctx( sctx_ ), // sctx{ sctx_ } - clang-3.6: no viable conversion from 'boost::context::stack_context' to 'std::size_t'
  74         main_ctx{ false } {
  75     }
  76
  77     virtual ~ecv1_activation_record() = default;
  78
  79     bool is_main_context() const noexcept {
  80         return main_ctx;
  81     }
  82
  83     void * resume( void * vp) {
  84         // store current activation record in local variable
  85         auto from = current().get();
  86         // store `this` in static, thread local pointer
  87         // `this` will become the active (running) context
  88         // returned by execution_context::current()
  89         current() = this;
  90 #if defined(BOOST_USE_SEGMENTED_STACKS)
  91         // adjust segmented stack properties
  92         __splitstack_getcontext( from->sctx.segments_ctx);
  93         __splitstack_setcontext( sctx.segments_ctx);
  94 #endif
  95         ecv1_data_t d = { from, vp };
  96         // context switch from parent context to `this`-context
  97         transfer_t t = jump_fcontext( fctx, & d);
  98         ecv1_data_t * dp = reinterpret_cast< ecv1_data_t * >( t.data);
  99         dp->from->fctx = t.fctx;
 100         // parent context resumed
 101         return dp->data;
 102     }
 103
 104     template< typename Fn >
 105     void * resume_ontop( void *  data, Fn && fn) {
 106         // store current activation record in local variable
 107         ecv1_activation_record * from = current().get();
 108         // store `this` in static, thread local pointer
 109         // `this` will become the active (running) context
 110         // returned by execution_context::current()
 111         current() = this;
 112 #if defined(BOOST_USE_SEGMENTED_STACKS)
 113         // adjust segmented stack properties
 114         __splitstack_getcontext( from->sctx.segments_ctx);
 115         __splitstack_setcontext( sctx.segments_ctx);
 116 #endif
 117         std::tuple< void *, Fn > p = std::forward_as_tuple( data, fn);
 118         ecv1_data_t d = { from, & p };
 119         // context switch from parent context to `this`-context
 120         // execute Fn( Tpl) on top of `this`
 121         transfer_t t = ontop_fcontext( fctx, & d, ecv1_context_ontop< Fn >);
 122         ecv1_data_t * dp = reinterpret_cast< ecv1_data_t * >( t.data);
 123         dp->from->fctx = t.fctx;
 124         // parent context resumed
 125         return dp->data;
 126     }
 127
 128     virtual void deallocate() noexcept {
 129     }
 130
 131     friend void intrusive_ptr_add_ref( ecv1_activation_record * ar) noexcept {
 132         ++ar->use_count;
 133     }
 134
 135     friend void intrusive_ptr_release( ecv1_activation_record * ar) noexcept {
 136         BOOST_ASSERT( nullptr != ar);
 137         if ( 0 == --ar->use_count) {
 138             ar->deallocate();
 139         }
 140     }
 141 };
 142
 143 struct BOOST_CONTEXT_DECL ecv1_activation_record_initializer {
 144     ecv1_activation_record_initializer() noexcept;
 145     ~ecv1_activation_record_initializer();
 146 };
 147
 148 template< typename Fn >
 149 transfer_t ecv1_context_ontop( transfer_t t) {
 150     ecv1_data_t * dp = reinterpret_cast< ecv1_data_t * >( t.data);
 151     dp->from->fctx = t.fctx;
 152     auto tpl = reinterpret_cast< std::tuple< void *, Fn > * >( dp->data);
 153     BOOST_ASSERT( nullptr != tpl);
 154     auto data = std::get< 0 >( * tpl);
 155     typename std::decay< Fn >::type fn = std::forward< Fn >( std::get< 1 >( * tpl) );
 156 #if defined(BOOST_NO_CXX17_STD_APPLY)
 157     dp->data = boost::context::detail::apply( fn, std::tie( data) );
 158 #else
 159     dp->data = std::apply( fn, std::tie( data) );
 160 #endif
 161     return { t.fctx, dp };
 162 }
 163
 164 template< typename StackAlloc, typename Fn, typename ... Args >
 165 class ecv1_capture_record : public ecv1_activation_record {
 166 private:
 167     typename std::decay< StackAlloc >::type             salloc_;
 168     typename std::decay< Fn >::type                     fn_;
 169     std::tuple< typename std::decay< Args >::type ... > args_;
 170     ecv1_activation_record                               *   caller_;
 171
 172     static void destroy( ecv1_capture_record * p) noexcept {
 173         typename std::decay< StackAlloc >::type salloc = std::move( p->salloc_);
 174         stack_context sctx = p->sctx;
 175         // deallocate activation record
 176         p->~ecv1_capture_record();
 177         // destroy stack with stack allocator
 178         salloc.deallocate( sctx);
 179     }
 180
 181 public:
 182     ecv1_capture_record( stack_context sctx, StackAlloc && salloc,
 183                     fcontext_t fctx,
 184                     ecv1_activation_record * caller,
 185                     Fn && fn, Args && ... args) noexcept :
 186         ecv1_activation_record{ fctx, sctx },
 187         salloc_{ std::forward< StackAlloc >( salloc) },
 188         fn_( std::forward< Fn >( fn) ),
 189         args_( std::forward< Args >( args) ... ),
 190         caller_{ caller } {
 191     }
 192
 193     void deallocate() noexcept override final {
 194         destroy( this);
 195     }
 196
 197     void run() {
 198         auto data = caller_->resume( nullptr);
 199 #if defined(BOOST_NO_CXX17_STD_APPLY)
 200         boost::context::detail::apply( fn_, std::tuple_cat( args_, std::tie( data) ) );
 201 #else
 202         std::apply( fn_, std::tuple_cat( args_, std::tie( data) ) );
 203 #endif
 204         BOOST_ASSERT_MSG( ! main_ctx, "main-context does not execute activation-record::run()");
 205     }
 206 };
 207
 208 }
 209
 210 namespace v1 {
 211
 212 class BOOST_CONTEXT_DECL execution_context {
 213 private:
 214     // tampoline function
 215     // entered if the execution context
 216     // is resumed for the first time
 217     template< typename AR >
 218     static void entry_func( detail::transfer_t t) noexcept {
 219         detail::ecv1_data_t * dp = reinterpret_cast< detail::ecv1_data_t * >( t.data);
 220         AR * ar = static_cast< AR * >( dp->data);
 221         BOOST_ASSERT( nullptr != ar);
 222         dp->from->fctx = t.fctx;
 223         // start execution of toplevel context-function
 224         ar->run();
 225     }
 226
 227     typedef boost::intrusive_ptr< detail::ecv1_activation_record >    ptr_t;
 228
 229     ptr_t   ptr_;
 230
 231     template< typename StackAlloc, typename Fn, typename ... Args >
 232     static detail::ecv1_activation_record * create_context( StackAlloc && salloc,
 233                                                        Fn && fn, Args && ... args) {
 234         typedef detail::ecv1_capture_record<
 235             StackAlloc, Fn, Args ...
 236         >                                           capture_t;
 237
 238         auto sctx = salloc.allocate();
 239         // reserve space for control structure
 240 #if defined(BOOST_NO_CXX11_CONSTEXPR) || defined(BOOST_NO_CXX11_STD_ALIGN)
 241         const std::size_t size = sctx.size - sizeof( capture_t);
 242         void * sp = static_cast< char * >( sctx.sp) - sizeof( capture_t);
 243 #else
 244         constexpr std::size_t func_alignment = 64; // alignof( capture_t);
 245         constexpr std::size_t func_size = sizeof( capture_t);
 246         // reserve space on stack
 247         void * sp = static_cast< char * >( sctx.sp) - func_size - func_alignment;
 248         // align sp pointer
 249         std::size_t space = func_size + func_alignment;
 250         sp = std::align( func_alignment, func_size, sp, space);
 251         BOOST_ASSERT( nullptr != sp);
 252         // calculate remaining size
 253         const std::size_t size = sctx.size - ( static_cast< char * >( sctx.sp) - static_cast< char * >( sp) );
 254 #endif
 255         // create fast-context
 256         const detail::fcontext_t fctx = detail::make_fcontext( sp, size, & execution_context::entry_func< capture_t >);
 257         BOOST_ASSERT( nullptr != fctx);
 258         // get current activation record
 259         auto curr = execution_context::current().ptr_;
 260         // placment new for control structure on fast-context stack
 261         return ::new ( sp) capture_t{
 262                 sctx, std::forward< StackAlloc >( salloc), fctx, curr.get(), std::forward< Fn >( fn), std::forward< Args >( args) ... };
 263     }
 264
 265     template< typename StackAlloc, typename Fn, typename ... Args >
 266     static detail::ecv1_activation_record * create_context( preallocated palloc, StackAlloc && salloc,
 267                                                        Fn && fn, Args && ... args) {
 268         typedef detail::ecv1_capture_record<
 269             StackAlloc, Fn, Args ...
 270         >                                           capture_t;
 271
 272         // reserve space for control structure
 273 #if defined(BOOST_NO_CXX11_CONSTEXPR) || defined(BOOST_NO_CXX11_STD_ALIGN)
 274         const std::size_t size = palloc.size - sizeof( capture_t);
 275         void * sp = static_cast< char * >( palloc.sp) - sizeof( capture_t);
 276 #else
 277         constexpr std::size_t func_alignment = 64; // alignof( capture_t);
 278         constexpr std::size_t func_size = sizeof( capture_t);
 279         // reserve space on stack
 280         void * sp = static_cast< char * >( palloc.sp) - func_size - func_alignment;
 281         // align sp pointer
 282         std::size_t space = func_size + func_alignment;
 283         sp = std::align( func_alignment, func_size, sp, space);
 284         BOOST_ASSERT( nullptr != sp);
 285         // calculate remaining size
 286         const std::size_t size = palloc.size - ( static_cast< char * >( palloc.sp) - static_cast< char * >( sp) );
 287 #endif
 288         // create fast-context
 289         const detail::fcontext_t fctx = detail::make_fcontext( sp, size, & execution_context::entry_func< capture_t >);
 290         BOOST_ASSERT( nullptr != fctx);
 291         // get current activation record
 292         auto curr = execution_context::current().ptr_;
 293         // placment new for control structure on fast-context stack
 294         return ::new ( sp) capture_t{
 295                 palloc.sctx, std::forward< StackAlloc >( salloc), fctx, curr.get(), std::forward< Fn >( fn), std::forward< Args >( args) ... };
 296     }
 297
 298     execution_context() noexcept :
 299         // default constructed with current ecv1_activation_record
 300         ptr_{ detail::ecv1_activation_record::current() } {
 301     }
 302
 303 public:
 304     static execution_context current() noexcept;
 305
 306 #if defined(BOOST_USE_SEGMENTED_STACKS)
 307     template< typename Fn,
 308               typename ... Args,
 309               typename = detail::disable_overload< execution_context, Fn >
 310     >
 311     execution_context( Fn && fn, Args && ... args) :
 312         // deferred execution of fn and its arguments
 313         // arguments are stored in std::tuple<>
 314         // non-type template parameter pack via std::index_sequence_for<>
 315         // preserves the number of arguments
 316         // used to extract the function arguments from std::tuple<>
 317         ptr_{ create_context( segmented_stack(),
 318                               std::forward< Fn >( fn),
 319                               std::forward< Args >( args) ...) } {
 320         ptr_->resume( ptr_.get() );
 321     }
 322
 323     template< typename Fn,
 324               typename ... Args
 325     >
 326     execution_context( std::allocator_arg_t, segmented_stack salloc, Fn && fn, Args && ... args) :
 327         // deferred execution of fn and its arguments
 328         // arguments are stored in std::tuple<>
 329         // non-type template parameter pack via std::index_sequence_for<>
 330         // preserves the number of arguments
 331         // used to extract the function arguments from std::tuple<>
 332         ptr_{ create_context( salloc,
 333                               std::forward< Fn >( fn),
 334                               std::forward< Args >( args) ...) } {
 335         ptr_->resume( ptr_.get() );
 336     }
 337
 338     template< typename Fn,
 339               typename ... Args
 340     >
 341     execution_context( std::allocator_arg_t, preallocated palloc, segmented_stack salloc, Fn && fn, Args && ... args) :
 342         // deferred execution of fn and its arguments
 343         // arguments are stored in std::tuple<>
 344         // non-type template parameter pack via std::index_sequence_for<>
 345         // preserves the number of arguments
 346         // used to extract the function arguments from std::tuple<>
 347         ptr_{ create_context( palloc, salloc,
 348                               std::forward< Fn >( fn),
 349                               std::forward< Args >( args) ...) } {
 350         ptr_->resume( ptr_.get() );
 351     }
 352 #else
 353     template< typename Fn,
 354               typename ... Args,
 355               typename = detail::disable_overload< execution_context, Fn >
 356     >
 357     execution_context( Fn && fn, Args && ... args) :
 358         // deferred execution of fn and its arguments
 359         // arguments are stored in std::tuple<>
 360         // non-type template parameter pack via std::index_sequence_for<>
 361         // preserves the number of arguments
 362         // used to extract the function arguments from std::tuple<>
 363         ptr_{ create_context( fixedsize_stack(),
 364                               std::forward< Fn >( fn),
 365                               std::forward< Args >( args) ...) } {
 366         ptr_->resume( ptr_.get() );
 367     }
 368
 369     template< typename StackAlloc,
 370               typename Fn,
 371               typename ... Args
 372     >
 373     execution_context( std::allocator_arg_t, StackAlloc && salloc, Fn && fn, Args && ... args) :
 374         // deferred execution of fn and its arguments
 375         // arguments are stored in std::tuple<>
 376         // non-type template parameter pack via std::index_sequence_for<>
 377         // preserves the number of arguments
 378         // used to extract the function arguments from std::tuple<>
 379         ptr_{ create_context( std::forward< StackAlloc >( salloc),
 380                               std::forward< Fn >( fn),
 381                               std::forward< Args >( args) ...) } {
 382         ptr_->resume( ptr_.get() );
 383     }
 384
 385     template< typename StackAlloc,
 386               typename Fn,
 387               typename ... Args
 388     >
 389     execution_context( std::allocator_arg_t, preallocated palloc, StackAlloc && salloc, Fn && fn, Args && ... args) :
 390         // deferred execution of fn and its arguments
 391         // arguments are stored in std::tuple<>
 392         // non-type template parameter pack via std::index_sequence_for<>
 393         // preserves the number of arguments
 394         // used to extract the function arguments from std::tuple<>
 395         ptr_{ create_context( palloc, std::forward< StackAlloc >( salloc),
 396                               std::forward< Fn >( fn),
 397                               std::forward< Args >( args) ...) } {
 398         ptr_->resume( ptr_.get() );
 399     }
 400 #endif
 401
 402     execution_context( execution_context const& other) noexcept :
 403         ptr_{ other.ptr_ } {
 404     }
 405
 406     execution_context( execution_context && other) noexcept :
 407         ptr_{ other.ptr_ } {
 408         other.ptr_.reset();
 409     }
 410
 411     execution_context & operator=( execution_context const& other) noexcept {
 412         // intrusive_ptr<> does not test for self-assignment
 413         if ( this == & other) return * this;
 414         ptr_ = other.ptr_;
 415         return * this;
 416     }
 417
 418     execution_context & operator=( execution_context && other) noexcept {
 419         if ( this == & other) return * this;
 420         execution_context tmp{ std::move( other) };
 421         swap( tmp);
 422         return * this;
 423     }
 424
 425     void * operator()( void * vp = nullptr) {
 426         return ptr_->resume( vp);
 427     }
 428
 429     template< typename Fn >
 430     void * operator()( exec_ontop_arg_t, Fn && fn, void * vp = nullptr) {
 431         return ptr_->resume_ontop( vp,
 432                                    std::forward< Fn >( fn) );
 433     }
 434
 435     explicit operator bool() const noexcept {
 436         return nullptr != ptr_.get();
 437     }
 438
 439     bool operator!() const noexcept {
 440         return nullptr == ptr_.get();
 441     }
 442
 443     bool operator==( execution_context const& other) const noexcept {
 444         return ptr_ == other.ptr_;
 445     }
 446
 447     bool operator!=( execution_context const& other) const noexcept {
 448         return ptr_ != other.ptr_;
 449     }
 450
 451     bool operator<( execution_context const& other) const noexcept {
 452         return ptr_ < other.ptr_;
 453     }
 454
 455     bool operator>( execution_context const& other) const noexcept {
 456         return other.ptr_ < ptr_;
 457     }
 458
 459     bool operator<=( execution_context const& other) const noexcept {
 460         return ! ( * this > other);
 461     }
 462
 463     bool operator>=( execution_context const& other) const noexcept {
 464         return ! ( * this < other);
 465     }
 466
 467     template< typename charT, class traitsT >
 468     friend std::basic_ostream< charT, traitsT > &
 469     operator<<( std::basic_ostream< charT, traitsT > & os, execution_context const& other) {
 470         if ( nullptr != other.ptr_) {
 471             return os << other.ptr_;
 472         } else {
 473             return os << "{not-a-context}";
 474         }
 475     }
 476
 477     void swap( execution_context & other) noexcept {
 478         ptr_.swap( other.ptr_);
 479     }
 480 };
 481
 482 inline
 483 void swap( execution_context & l, execution_context & r) noexcept {
 484     l.swap( r);
 485 }
 486
 487 }}}
 488
 489 #ifdef BOOST_HAS_ABI_HEADERS
 490 # include BOOST_ABI_SUFFIX
 491 #endif
 492
 493 #endif // BOOST_CONTEXT_EXECUTION_CONTEXT_V1_H