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async.c revision 1.2.4.2 
      1 /*	$NetBSD: async.c,v 1.2.4.2 2025/08/02 05:53:51 perseant Exp $	*/
      2 
      3 /*
      4  * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
      5  *
      6  * SPDX-License-Identifier: MPL-2.0
      7  *
      8  * This Source Code Form is subject to the terms of the Mozilla Public
      9  * License, v. 2.0. If a copy of the MPL was not distributed with this
     10  * file, you can obtain one at https://mozilla.org/MPL/2.0/.
     11  *
     12  * See the COPYRIGHT file distributed with this work for additional
     13  * information regarding copyright ownership.
     14  */
     15 
     16 #include <stdlib.h>
     17 #include <sys/types.h>
     18 #include <unistd.h>
     19 
     20 #include <isc/async.h>
     21 #include <isc/atomic.h>
     22 #include <isc/barrier.h>
     23 #include <isc/condition.h>
     24 #include <isc/job.h>
     25 #include <isc/loop.h>
     26 #include <isc/magic.h>
     27 #include <isc/mem.h>
     28 #include <isc/mutex.h>
     29 #include <isc/refcount.h>
     30 #include <isc/result.h>
     31 #include <isc/signal.h>
     32 #include <isc/strerr.h>
     33 #include <isc/thread.h>
     34 #include <isc/util.h>
     35 #include <isc/uv.h>
     36 #include <isc/work.h>
     37 
     38 #include "async_p.h"
     39 #include "job_p.h"
     40 #include "loop_p.h"
     41 
     42 void
     43 isc_async_run(isc_loop_t *loop, isc_job_cb cb, void *cbarg) {
     44 	REQUIRE(VALID_LOOP(loop));
     45 	REQUIRE(cb != NULL);
     46 
     47 	isc_job_t *job = isc_mem_get(loop->mctx, sizeof(*job));
     48 	*job = (isc_job_t){
     49 		.cb = cb,
     50 		.cbarg = cbarg,
     51 	};
     52 
     53 	cds_wfcq_node_init(&job->wfcq_node);
     54 
     55 	/*
     56 	 * cds_wfcq_enqueue() is non-blocking and enqueues the job to async
     57 	 * queue.
     58 	 *
     59 	 * The function returns 'false' in case the queue was empty - in such
     60 	 * case we need to trigger the async callback.
     61 	 */
     62 	if (!cds_wfcq_enqueue(&loop->async_jobs.head, &loop->async_jobs.tail,
     63 			      &job->wfcq_node))
     64 	{
     65 		int r = uv_async_send(&loop->async_trigger);
     66 		UV_RUNTIME_CHECK(uv_async_send, r);
     67 	}
     68 }
     69 
     70 void
     71 isc__async_cb(uv_async_t *handle) {
     72 	isc_loop_t *loop = uv_handle_get_data(handle);
     73 	isc_jobqueue_t jobs;
     74 
     75 	REQUIRE(VALID_LOOP(loop));
     76 
     77 	/* Initialize local wfcqueue */
     78 	__cds_wfcq_init(&jobs.head, &jobs.tail);
     79 
     80 	/*
     81 	 * Move all the elements from loop->async_jobs to a local jobs queue.
     82 	 *
     83 	 * __cds_wfcq_splice_blocking() assumes that synchronization is
     84 	 * done externally - there's no internal locking, unlike
     85 	 * cds_wfcq_splice_blocking(), and we do not need to check whether
     86 	 * it needs to block, unlike __cds_wfcq_splice_nonblocking().
     87 	 *
     88 	 * The reason we can use __cds_wfcq_splice_blocking() is that the
     89 	 * only other function we use is cds_wfcq_enqueue() which doesn't
     90 	 * require any synchronization (see the table in urcu/wfcqueue.h
     91 	 * for more details).
     92 	 */
     93 	enum cds_wfcq_ret ret = __cds_wfcq_splice_blocking(
     94 		&jobs.head, &jobs.tail, &loop->async_jobs.head,
     95 		&loop->async_jobs.tail);
     96 	INSIST(ret != CDS_WFCQ_RET_WOULDBLOCK);
     97 	if (ret == CDS_WFCQ_RET_SRC_EMPTY) {
     98 		/*
     99 		 * Nothing to do, the source queue was empty - most
    100 		 * probably we were called from isc__async_close() below.
    101 		 */
    102 		return;
    103 	}
    104 
    105 	/*
    106 	 * Walk through the local queue which has now all the members copied
    107 	 * locally, and call the callbacks and free all the isc_job_t(s).
    108 	 */
    109 	struct cds_wfcq_node *node, *next;
    110 	__cds_wfcq_for_each_blocking_safe(&jobs.head, &jobs.tail, node, next) {
    111 		isc_job_t *job = caa_container_of(node, isc_job_t, wfcq_node);
    112 
    113 		job->cb(job->cbarg);
    114 
    115 		isc_mem_put(loop->mctx, job, sizeof(*job));
    116 	}
    117 }
    118 
    119 void
    120 isc__async_close(uv_handle_t *handle) {
    121 	isc_loop_t *loop = uv_handle_get_data(handle);
    122 
    123 	isc__async_cb(&loop->async_trigger);
    124 }
    125