221 lines
6.5 KiB
C
221 lines
6.5 KiB
C
/* fibers.c -- extremely simple lightweight thread (fiber) implementation
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Copyright (C) 2016-2019 Free Software Foundation, Inc.
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Contributed by Pekka Jaaskelainen <pekka.jaaskelainen@parmance.com>
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for General Processor Tech.
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Copyright (C) 2015-2019 Free Software Foundation, Inc.
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Contributed by Pekka Jaaskelainen <pekka.jaaskelainen@parmance.com>
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for General Processor Tech.
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Permission is hereby granted, free of charge, to any person obtaining a
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copy of this software and associated documentation files
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(the "Software"), to deal in the Software without restriction, including
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without limitation the rights to use, copy, modify, merge, publish,
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distribute, sublicense, and/or sell copies of the Software, and to
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permit persons to whom the Software is furnished to do so, subject to
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the following conditions:
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The above copyright notice and this permission notice shall be included
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in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
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DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
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OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
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USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <stdint.h>
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#include "target-config.h"
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#include "fibers.h"
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void
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phsa_fatal_error (int code);
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ucontext_t main_context;
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/* The last fiber in the linked list. */
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static fiber_t *tail_fiber = NULL;
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/* The first fiber in the linked list. */
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static fiber_t *head_fiber = NULL;
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/* The fiber currently being executed. */
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static fiber_t *current_fiber = NULL;
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/* Makecontext accepts only integer arguments. We need to split the
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pointer argument in case pointer does not fit into int. This helper
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function can be used to restore the pointer from the arguments. */
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void *
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fiber_int_args_to_ptr (int arg0, int arg1)
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{
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void *ptr = NULL;
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#if SIZEOF_VOIDP == 8 && SIZEOF_INT == 4
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ptr = (void*)(((uint64_t) arg0 & (uint64_t) 0xFFFFFFFF)
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| ((uint64_t) arg1 << 32));
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#elif SIZEOF_VOIDP == 4 && SIZEOF_INT == 4
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ptr = (void*)arg0;
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#else
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# error Unsupported pointer/int size.
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#endif
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return ptr;
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}
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void
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fiber_init (fiber_t *fiber, fiber_function_t start_function, void *arg,
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size_t stack_size, size_t stack_align)
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{
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int arg0, arg1;
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if (getcontext (&fiber->context) != 0)
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phsa_fatal_error (3);
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if (posix_memalign (&fiber->context.uc_stack.ss_sp, stack_align, stack_size)
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!= 0)
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phsa_fatal_error (4);
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fiber->context.uc_stack.ss_size = stack_size;
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fiber->context.uc_link = &main_context;
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/* makecontext () accepts only integer arguments. Split the
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pointer argument to two args in the case pointer does not fit
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into one int. */
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#if SIZEOF_VOIDP == 8 && SIZEOF_INT == 4
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arg0 = (int32_t) 0xFFFFFFFF & (uint64_t)arg;
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arg1 = (int32_t) 0xFFFFFFFF & ((uint64_t)arg >> 32);
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#elif SIZEOF_VOIDP == 4 && SIZEOF_INT == 4
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arg0 = (int)arg;
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arg1 = 0;
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#else
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# error Unsupported pointer/int size.
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#endif
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makecontext (&fiber->context, (void*)start_function, 2, arg0, arg1);
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fiber->status = FIBER_STATUS_READY;
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fiber->next = NULL;
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fiber->prev = NULL;
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/* Create a linked list of the created fibers. Append the new one at
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the end. */
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if (tail_fiber == NULL)
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tail_fiber = fiber;
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else
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{
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tail_fiber->next = fiber;
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fiber->prev = tail_fiber;
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tail_fiber = fiber;
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}
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if (head_fiber == NULL)
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head_fiber = fiber;
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}
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void
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fiber_exit ()
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{
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fiber_status_t old_status = current_fiber->status;
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current_fiber->status = FIBER_STATUS_EXITED;
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if (old_status == FIBER_STATUS_JOINED)
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/* In case this thread has been joined, return back to the joiner. */
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swapcontext (¤t_fiber->context, &main_context);
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else
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/* In case the thread exited while being yielded from another thread,
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switch back to another fiber. */
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fiber_yield ();
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}
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void
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fiber_join (fiber_t *fiber)
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{
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fiber_t *next_ready_fiber = NULL;
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current_fiber = fiber;
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if (fiber->status != FIBER_STATUS_EXITED)
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{
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fiber->status = FIBER_STATUS_JOINED;
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while (fiber->status != FIBER_STATUS_EXITED)
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swapcontext (&main_context, &fiber->context);
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}
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/* Remove the successfully joined fiber from the linked list so we won't
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access it later (the fiber itself might be freed after the join). */
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if (fiber->prev != NULL)
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fiber->prev->next = fiber->next;
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if (fiber->next != NULL)
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fiber->next->prev = fiber->prev;
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if (head_fiber == fiber)
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head_fiber = fiber->next;
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if (tail_fiber == fiber)
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tail_fiber = fiber->prev;
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free (fiber->context.uc_stack.ss_sp);
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}
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void
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fiber_yield ()
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{
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fiber_t *next_ready_fiber = current_fiber;
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if (current_fiber == head_fiber
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&& current_fiber == tail_fiber)
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{
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/* If the last fiber exits independently, there is no
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fiber to switch to. Switch to the main context in that
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case. */
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if (current_fiber->status == FIBER_STATUS_EXITED)
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swapcontext (¤t_fiber->context, &main_context);
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}
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do {
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next_ready_fiber = next_ready_fiber->next != NULL
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? next_ready_fiber->next : head_fiber;
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} while (next_ready_fiber != current_fiber
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&& next_ready_fiber->status == FIBER_STATUS_EXITED);
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fiber_t *old_current_fiber = current_fiber;
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current_fiber = next_ready_fiber;
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swapcontext (&old_current_fiber->context, &next_ready_fiber->context);
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}
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size_t
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fiber_barrier_reach (fiber_barrier_t *barrier)
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{
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/* Yield once to ensure that there are no fibers waiting for
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a previous triggering of the barrier in the waiting_count
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loop. This should release them before we update the reached
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counter again. */
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fiber_yield ();
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barrier->reached++;
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++barrier->waiting_count;
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while (barrier->reached < barrier->threshold)
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fiber_yield ();
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--barrier->waiting_count;
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/* Wait until all the fibers have reached this point. */
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while (barrier->waiting_count > 0)
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fiber_yield ();
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/* Now all fibers have been released from the barrier waiting
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loop. We can now safely reset the reach count for new triggering. */
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if (barrier->reached > 0)
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{
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barrier->reached = 0;
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return 0;
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}
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return 1;
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}
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void
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fiber_barrier_init (fiber_barrier_t *barrier, size_t threshold)
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{
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barrier->threshold = threshold;
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barrier->waiting_count = 0;
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barrier->reached = 0;
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}
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