| /* |
| * (C) 2021 by sysmocom s.f.m.c. GmbH <info@sysmocom.de> |
| * All Rights Reserved |
| * |
| * Author: Eric Wild |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU Affero General Public License as published by |
| * the Free Software Foundation; either version 3 of the License, or |
| * (at your option) any later version. |
| * |
| * This program 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. See the |
| * GNU Affero General Public License for more details. |
| * |
| * You should have received a copy of the GNU Affero General Public License |
| * along with this program. If not, see <http://www.gnu.org/licenses/>. |
| * |
| */ |
| |
| #include <inttypes.h> |
| #include <stdatomic.h> |
| #include <stdbool.h> |
| #include <stdint.h> |
| #include <stdlib.h> |
| #include <string.h> |
| #include <sys/eventfd.h> |
| #include <sys/types.h> |
| #include <unistd.h> |
| #include <talloc.h> |
| |
| #include <osmocom/mgcp/mgcp_threads_queue.h> |
| |
| /* |
| classic lamport circular lockfree spsc queue: |
| every "side" only writes its own ptr, but may read the other sides ptr |
| |
| notify reader using eventfd as soon as element is added, reader then reads until |
| read fails |
| -> reader pops in a loop until FALSE and might get spurious events because it |
| read before it was notified, which is fine |
| -> writing pushes *the same data* in a loop until TRUE, blocks |
| |
| shutting this down requires |
| 1) to stop reading and pushing |
| 2) ONE side to take care of the eventfds |
| */ |
| |
| static struct spsc *spsc_init(void *talloc_ctx, unsigned int count, unsigned int size_per_buf, bool blockr, bool blockw) |
| { |
| struct spsc *q = talloc_zero_size(talloc_ctx, sizeof(struct spsc) + sizeof(uintptr_t) * count); |
| atomic_init(&q->readptr, 0); |
| atomic_init(&q->writeptr, 0); |
| q->efd_r = eventfd(0, blockr ? 0 : EFD_NONBLOCK); |
| q->efd_w = eventfd(1, blockw ? 0 : EFD_NONBLOCK); |
| q->count = count; |
| q->size_per_buf = size_per_buf; |
| q->buf = talloc_zero_size(q, size_per_buf * count); |
| |
| for (int i = 0; i < count; i++) |
| q->data[i] = (uintptr_t)q->buf + i * size_per_buf; |
| return q; |
| } |
| |
| static void spsc_deinit(struct spsc *q) |
| { |
| talloc_free(q->buf); |
| close(q->efd_r); |
| close(q->efd_w); |
| talloc_free(q); |
| } |
| |
| static ssize_t spsc_check_r(struct spsc *q) |
| { |
| uint64_t efdr; |
| return read(q->efd_r, &efdr, sizeof(uint64_t)); |
| } |
| static ssize_t spsc_check_w(struct spsc *q) |
| { |
| uint64_t efdr; |
| return read(q->efd_w, &efdr, sizeof(uint64_t)); |
| } |
| static void spsc_notify_r(struct spsc *q) |
| { |
| uint64_t efdu = 1; |
| write(q->efd_r, &efdu, sizeof(uint64_t)); |
| } |
| static void spsc_notify_w(struct spsc *q) |
| { |
| uint64_t efdu = 1; |
| write(q->efd_w, &efdu, sizeof(uint64_t)); |
| } |
| |
| /*! Adds element to the queue by copying the data. |
| * \param[in] q queue. |
| * \param[in] elem input buffer, must match the originally configured queue buffer size!. |
| * \returns true if queue was not full and element was successfully pushed */ |
| bool spsc_push(struct spsc *q, void *elem) |
| { |
| size_t cur_wp, cur_rp; |
| cur_wp = atomic_load_explicit(&q->writeptr, memory_order_relaxed); |
| cur_rp = atomic_load_explicit(&q->readptr, memory_order_acquire); |
| if ((cur_wp + 1) % q->count == cur_rp) { |
| spsc_check_w(q); /* blocks, ensures next (!) call succeeds */ |
| return false; |
| } |
| memcpy((void *)q->data[cur_wp], elem, q->size_per_buf); |
| atomic_store_explicit(&q->writeptr, (cur_wp + 1) % q->count, memory_order_release); |
| spsc_notify_r(q); /* fine after release */ |
| return true; |
| } |
| |
| /*! Reads the read-fd of the queue, which, depending on settings passed on queue creation, blocks. |
| * This function can be used to deliberately wait for a non-empty queue on the read side. |
| * \param[in] q queue. |
| * \returns result of reading the fd. */ |
| ssize_t spsc_prep_pop(struct spsc *q) |
| { |
| return spsc_check_r(q); |
| } |
| |
| /*! Removes element from the queue by copying the data. |
| * \param[in] q queue. |
| * \param[in] elem output buffer, must match the originally configured queue buffer size!. |
| * \returns true if queue was not empty and element was successfully removed */ |
| bool spsc_pop(struct spsc *q, void *elem) |
| { |
| size_t cur_wp, cur_rp; |
| cur_wp = atomic_load_explicit(&q->writeptr, memory_order_acquire); |
| cur_rp = atomic_load_explicit(&q->readptr, memory_order_relaxed); |
| |
| if (cur_wp == cur_rp) /* blocks via prep_pop */ |
| return false; |
| memcpy(elem, (void *)q->data[cur_rp], q->size_per_buf); |
| atomic_store_explicit(&q->readptr, (cur_rp + 1) % q->count, memory_order_release); |
| spsc_notify_w(q); |
| return true; |
| } |
| |
| /*! Creates a bidirectional queue channel that consists of two queues, one in each direction, |
| * commonly referred to as a and b side. |
| * \param[in] talloc_ctx allocation context. |
| * \param[in] count number of buffers per queue. |
| * \param[in] size_per_buf size of buffers per queue. |
| * \param[in] blockr_a should reading the a-side read fd block?. |
| * \param[in] blockw_a should reading the a-side write fd block?. |
| * \param[in] blockr_b should reading the b-side read fd block?. |
| * \param[in] blockw_b should reading the b-side write fd block?. |
| * \returns queue channel */ |
| struct qchan spsc_chan_init_ex(void *talloc_ctx, unsigned int count, unsigned int size_per_buf, bool blockr_a, |
| bool blockw_a, bool blockr_b, bool blockw_b) |
| { |
| struct qchan q; |
| q.a = spsc_init(talloc_ctx, count, size_per_buf, blockr_a, blockw_a); |
| q.b = spsc_init(talloc_ctx, count, size_per_buf, blockr_b, blockw_b); |
| return q; |
| } |
| |
| /*! Creates a bidirectional queue channel that consists of two queues, one in each direction, |
| * commonly referred to as a and b side. |
| * \param[in] talloc_ctx allocation context. |
| * \param[in] count number of buffers per queue. |
| * \param[in] size_per_buf size of buffers per queue. |
| * \returns queue channel */ |
| struct qchan spsc_chan_init(void *talloc_ctx, unsigned int count, unsigned int size_per_buf) |
| { |
| return spsc_chan_init_ex(talloc_ctx, count, size_per_buf, false, true, false, true); |
| } |
| |
| /*! Closes a bidirectional queue channel. |
| * \param[in] q queue */ |
| void spsc_chan_close(struct qchan *q) |
| { |
| spsc_deinit(q->a); |
| spsc_deinit(q->b); |
| free(q); |
| } |
| |
| /*! Gets queue channel read/write fd for a/b side according to function name. |
| * \param[in] q queue channel. |
| * \returns fd */ |
| int spsc_get_a_rdfd(struct qchan *q) |
| { |
| return q->a->efd_r; |
| } |
| /*! Gets queue channel read/write fd for a/b side according to function name. |
| * \param[in] q queue channel. |
| * \returns fd */ |
| int spsc_get_b_rdfd(struct qchan *q) |
| { |
| return q->b->efd_r; |
| } |
| /*! Gets queue channel read/write fd for a/b side according to function name. |
| * \param[in] q queue channel. |
| * \returns fd */ |
| int spsc_get_a_wrfd(struct qchan *q) |
| { |
| return q->a->efd_w; |
| } |
| /*! Gets queue channel read/write fd for a/b side according to function name. |
| * \param[in] q queue channel. |
| * \returns fd */ |
| int spsc_get_b_wrfd(struct qchan *q) |
| { |
| return q->b->efd_w; |
| } |