diff --git a/include/osmocom/mgcp/mgcp_threads_queue.h b/include/osmocom/mgcp/mgcp_threads_queue.h new file mode 100644 index 000000000..bf094f54d --- /dev/null +++ b/include/osmocom/mgcp/mgcp_threads_queue.h @@ -0,0 +1,52 @@ +/* + * (C) 2021 by sysmocom s.f.m.c. GmbH + * 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 . + * + */ + +#include +#include +#include + +struct spsc { + atomic_uint readptr; + atomic_uint writeptr; + + int efd_r, efd_w; /* eventfds used to block/notify readers/writers */ + + int count; + int size_per_buf; + + void *buf; /* buffer size count*size_per_buf */ + uintptr_t data[0]; /* count sized array of pointers to size_per_buf chunks in buf array*/ +}; + +struct qchan { + struct spsc *a; + struct spsc *b; +}; + +bool spsc_push(struct spsc *q, void *elem); +bool spsc_pop(struct spsc *q, void *elem); +ssize_t spsc_prep_pop(struct spsc *q); +int spsc_get_a_rdfd(struct qchan *q); + +struct qchan spsc_chan_init(void *talloc_ctx, unsigned int count, unsigned int size_per_buf); +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); +void spsc_chan_close(struct qchan *q); diff --git a/src/libosmo-mgcp/mgcp_threads_queue.c b/src/libosmo-mgcp/mgcp_threads_queue.c new file mode 100644 index 000000000..8d10e36c4 --- /dev/null +++ b/src/libosmo-mgcp/mgcp_threads_queue.c @@ -0,0 +1,207 @@ +/* + * (C) 2021 by sysmocom s.f.m.c. GmbH + * 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 . + * + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include + +/* +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; +}