source: libcfa/src/concurrency/coroutine.cfa@ b2f6113

//
// Cforall Version 1.0.0 Copyright (C) 2016 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// coroutine.c --
//
// Author           : Thierry Delisle
// Created On       : Mon Nov 28 12:27:26 2016
// Last Modified By : Peter A. Buhr
// Last Modified On : Fri Mar 30 17:20:57 2018
// Update Count     : 9
//

#include "coroutine.hfa"

extern "C" {
#include <stddef.h>
#include <malloc.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
// use this define to make unwind.h play nice, definetely a hack
#define HIDE_EXPORTS
#include <unwind.h>
#undef HIDE_EXPORTS
#include <sys/mman.h>
}

#include "kernel_private.hfa"

#define __CFA_INVOKE_PRIVATE__
#include "invoke.h"

extern "C" {
        void _CtxCoroutine_Unwind(struct _Unwind_Exception * storage, struct coroutine_desc *) __attribute__ ((__noreturn__));
        static void _CtxCoroutine_UnwindCleanup(_Unwind_Reason_Code, struct _Unwind_Exception *) __attribute__ ((__noreturn__));
        static void _CtxCoroutine_UnwindCleanup(_Unwind_Reason_Code, struct _Unwind_Exception *) {
                abort();
        }
}

//-----------------------------------------------------------------------------
// Global state variables

// minimum feasible stack size in bytes
#define MinStackSize 1000
extern size_t __page_size;                              // architecture pagesize HACK, should go in proper runtime singleton

void __stack_prepare( __stack_info_t * this, size_t create_size );

//-----------------------------------------------------------------------------
// Coroutine ctors and dtors
void ?{}( __stack_info_t & this, void * storage, size_t storageSize ) {
        this.storage   = (__stack_t *)storage;

        // Did we get a piece of storage ?
        if (this.storage || storageSize != 0) {
                // We either got a piece of storage or the user asked for a specific size
                // Immediately create the stack
                // (This is slightly unintuitive that non-default sized coroutines create are eagerly created
                // but it avoids that all coroutines carry an unnecessary size)
                verify( storageSize != 0 );
                __stack_prepare( &this, storageSize );
        }
}

void ^?{}(__stack_info_t & this) {
        if ( ! this.userStack && this.storage ) {
                void * storage = (char*)(this.storage) - this.storage->size;
                __cfaabi_dbg_debug_do(
                        storage = (char*)(storage) - __page_size;
                        if ( mprotect( storage, __page_size, PROT_READ | PROT_WRITE ) == -1 ) {
                                abort( "(coStack_t *)%p.^?{}() : internal error, mprotect failure, error(%d) %s.", &this, errno, strerror( errno ) );
                        }
                );
                __cfaabi_dbg_print_safe("Kernel : Deleting stack %p\n", storage);
                free( storage );
        }
}

void ?{}( coroutine_desc & this, const char * name, void * storage, size_t storageSize ) with( this ) {
        (this.stack){storage, storageSize};
        this.name = name;
        state = Start;
        starter = NULL;
        last = NULL;
        cancellation = NULL;
}

void ^?{}(coroutine_desc& this) {
        if(this.state != Halted && this.state != Start) {
                coroutine_desc * src = TL_GET( this_thread )->curr_cor;
                coroutine_desc * dst = &this;

                struct _Unwind_Exception storage;
                storage.exception_class = -1;
                storage.exception_cleanup = _CtxCoroutine_UnwindCleanup;
                this.cancellation = &storage;
                this.last = src;

                // not resuming self ?
                if ( src == dst ) {
                        abort( "Attempt by coroutine %.256s (%p) to terminate itself.\n", src->name, src );
                }

                CoroutineCtxSwitch( src, dst );
        }
}

// Part of the Public API
// Not inline since only ever called once per coroutine
forall(dtype T | is_coroutine(T))
void prime(T& cor) {
        coroutine_desc* this = get_coroutine(cor);
        assert(this->state == Start);

        this->state = Primed;
        resume(cor);
}

// Wrapper for co
void CoroutineCtxSwitch(coroutine_desc* src, coroutine_desc* dst) {
        // Safety note : Preemption must be disabled since there is a race condition
        // kernelTLS.this_thread->curr_cor and $rsp/$rbp must agree at all times
        verify( TL_GET( preemption_state.enabled ) || TL_GET( this_processor )->do_terminate );
        disable_interrupts();

        // set state of current coroutine to inactive
        src->state = src->state == Halted ? Halted : Inactive;

        // set new coroutine that task is executing
        TL_GET( this_thread )->curr_cor = dst;

        // context switch to specified coroutine
        CtxSwitch( &src->context, &dst->context );
        // when CtxSwitch returns we are back in the src coroutine

        // set state of new coroutine to active
        src->state = Active;

        enable_interrupts( __cfaabi_dbg_ctx );
        verify( TL_GET( preemption_state.enabled ) || TL_GET( this_processor )->do_terminate );

        if( unlikely(src->cancellation != NULL) ) {
                _CtxCoroutine_Unwind(src->cancellation, src);
        }
}

[void *, size_t] __stack_alloc( size_t storageSize ) {
        static const size_t stack_data_size = libCeiling( sizeof(__stack_t), 16 ); // minimum alignment
        assert(__page_size != 0l);
        size_t size = libCeiling( storageSize, 16 ) + stack_data_size;

        // If we are running debug, we also need to allocate a guardpage to catch stack overflows.
        void * storage;
        __cfaabi_dbg_debug_do(
                storage = memalign( __page_size, size + __page_size );
        );
        __cfaabi_dbg_no_debug_do(
                storage = (void*)malloc(size);
        );

        __cfaabi_dbg_print_safe("Kernel : Created stack %p of size %zu\n", storage, size);
        __cfaabi_dbg_debug_do(
                if ( mprotect( storage, __page_size, PROT_NONE ) == -1 ) {
                        abort( "__stack_alloc : internal error, mprotect failure, error(%d) %s.", (int)errno, strerror( (int)errno ) );
                }
                storage = (void *)(((intptr_t)storage) + __page_size);
        );

        verify( ((intptr_t)storage & (libAlign() - 1)) == 0ul );
        return [storage, size];
}

void __stack_prepare( __stack_info_t * this, size_t create_size ) {
        static const size_t stack_data_size = libCeiling( sizeof(__stack_t), 16 ); // minimum alignment
        bool userStack;
        void * storage;
        size_t size;
        if ( !this->storage ) {
                userStack = false;
                [storage, size] = __stack_alloc( create_size );
        } else {
                userStack = true;
                __cfaabi_dbg_print_safe("Kernel : stack obj %p using user stack %p(%zu bytes)\n", this, this->storage, this->storage->size);

                // The stack must be aligned, advance the pointer to the next align data
                storage = (void*)libCeiling( (intptr_t)this->storage, libAlign());

                // The size needs to be shrinked to fit all the extra data structure and be aligned
                ptrdiff_t diff = (intptr_t)storage - (intptr_t)this->storage;
                size = libFloor(create_size - stack_data_size - diff, libAlign());
        } // if
        assertf( size >= MinStackSize, "Stack size %zd provides less than minimum of %d bytes for a stack.", size, MinStackSize );

        this->storage = (__stack_t *)((intptr_t)storage + size);
        this->storage->size  = size;
        this->storage->limit = storage;
        this->storage->base  = (void*)((intptr_t)storage + size);
        this->userStack = userStack;
}

// We need to call suspend from invoke.c, so we expose this wrapper that
// is not inline (We can't inline Cforall in C)
extern "C" {
        void __suspend_internal(void) {
                suspend();
        }

        void __leave_coroutine( coroutine_desc * src ) {
                coroutine_desc * starter = src->cancellation != 0 ? src->last : src->starter;

                src->state = Halted;

                assertf( starter != 0,
                        "Attempt to suspend/leave coroutine \"%.256s\" (%p) that has never been resumed.\n"
                        "Possible cause is a suspend executed in a member called by a coroutine user rather than by the coroutine main.",
                        src->name, src );
                assertf( starter->state != Halted,
                        "Attempt by coroutine \"%.256s\" (%p) to suspend/leave back to terminated coroutine \"%.256s\" (%p).\n"
                        "Possible cause is terminated coroutine's main routine has already returned.",
                        src->name, src, starter->name, starter );

                CoroutineCtxSwitch( src, starter );
        }
}

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