/src/httpd/server/mpm_fdqueue.c

Source (jump to first uncovered line)
/* Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "mpm_fdqueue.h"

#if APR_HAS_THREADS

#include <apr_atomic.h>

static const apr_uint32_t zero_pt = APR_UINT32_MAX/2;

struct recycled_pool
{
    apr_pool_t *pool;
    struct recycled_pool *next;
};

struct fd_queue_info_t
{
    apr_uint32_t volatile idlers; /**
                                   * >= zero_pt: number of idle worker threads
                                   * <  zero_pt: number of threads blocked,
                                   *             waiting for an idle worker
                                   */
    apr_thread_mutex_t *idlers_mutex;
    apr_thread_cond_t *wait_for_idler;
    int terminated;
    int max_idlers;
    int max_recycled_pools;
    apr_uint32_t recycled_pools_count;
    struct recycled_pool *volatile recycled_pools;
};

struct fd_queue_elem_t
{
    apr_socket_t *sd;
    void *sd_baton;
    apr_pool_t *p;
};

static apr_status_t queue_info_cleanup(void *data_)
{
    fd_queue_info_t *qi = data_;
    apr_thread_cond_destroy(qi->wait_for_idler);
    apr_thread_mutex_destroy(qi->idlers_mutex);

    /* Clean up any pools in the recycled list */
    for (;;) {
        struct recycled_pool *first_pool = qi->recycled_pools;
        if (first_pool == NULL) {
            break;
        }
        if (apr_atomic_casptr((void *)&qi->recycled_pools, first_pool->next,
                              first_pool) == first_pool) {
            apr_pool_destroy(first_pool->pool);
        }
    }

    return APR_SUCCESS;
}

apr_status_t ap_queue_info_create(fd_queue_info_t **queue_info,
                                  apr_pool_t *pool, int max_idlers,
                                  int max_recycled_pools)
{
    apr_status_t rv;
    fd_queue_info_t *qi;

    qi = apr_pcalloc(pool, sizeof(*qi));

    rv = apr_thread_mutex_create(&qi->idlers_mutex, APR_THREAD_MUTEX_DEFAULT,
                                 pool);
    if (rv != APR_SUCCESS) {
        return rv;
    }
    rv = apr_thread_cond_create(&qi->wait_for_idler, pool);
    if (rv != APR_SUCCESS) {
        return rv;
    }
    qi->recycled_pools = NULL;
    qi->max_recycled_pools = max_recycled_pools;
    qi->max_idlers = max_idlers;
    qi->idlers = zero_pt;
    apr_pool_cleanup_register(pool, qi, queue_info_cleanup,
                              apr_pool_cleanup_null);

    *queue_info = qi;

    return APR_SUCCESS;
}

apr_status_t ap_queue_info_set_idle(fd_queue_info_t *queue_info,
                                    apr_pool_t *pool_to_recycle)
{
    apr_status_t rv;

    ap_queue_info_push_pool(queue_info, pool_to_recycle);

    /* If other threads are waiting on a worker, wake one up */
    if (apr_atomic_inc32(&queue_info->idlers) < zero_pt) {
        rv = apr_thread_mutex_lock(queue_info->idlers_mutex);
        if (rv != APR_SUCCESS) {
            AP_DEBUG_ASSERT(0);
            return rv;
        }
        rv = apr_thread_cond_signal(queue_info->wait_for_idler);
        if (rv != APR_SUCCESS) {
            apr_thread_mutex_unlock(queue_info->idlers_mutex);
            return rv;
        }
        rv = apr_thread_mutex_unlock(queue_info->idlers_mutex);
        if (rv != APR_SUCCESS) {
            return rv;
        }
    }

    return APR_SUCCESS;
}

apr_status_t ap_queue_info_try_get_idler(fd_queue_info_t *queue_info)
{
    /* Don't block if there isn't any idle worker. */
    for (;;) {
        apr_uint32_t idlers = queue_info->idlers;
        if (idlers <= zero_pt) {
            return APR_EAGAIN;
        }
        if (apr_atomic_cas32(&queue_info->idlers, idlers - 1,
                             idlers) == idlers) {
            return APR_SUCCESS;
        }
    }
}

apr_status_t ap_queue_info_wait_for_idler(fd_queue_info_t *queue_info,
                                          int *had_to_block)
{
    apr_status_t rv;

    /* Block if there isn't any idle worker.
     * apr_atomic_add32(x, -1) does the same as dec32(x), except
     * that it returns the previous value (unlike dec32's bool).
     */
    if (apr_atomic_add32(&queue_info->idlers, -1) <= zero_pt) {
        rv = apr_thread_mutex_lock(queue_info->idlers_mutex);
        if (rv != APR_SUCCESS) {
            AP_DEBUG_ASSERT(0);
            apr_atomic_inc32(&(queue_info->idlers));    /* back out dec */
            return rv;
        }
        /* Re-check the idle worker count to guard against a
         * race condition.  Now that we're in the mutex-protected
         * region, one of two things may have happened:
         *   - If the idle worker count is still negative, the
         *     workers are all still busy, so it's safe to
         *     block on a condition variable.
         *   - If the idle worker count is non-negative, then a
         *     worker has become idle since the first check
         *     of queue_info->idlers above.  It's possible
         *     that the worker has also signaled the condition
         *     variable--and if so, the listener missed it
         *     because it wasn't yet blocked on the condition
         *     variable.  But if the idle worker count is
         *     now non-negative, it's safe for this function to
         *     return immediately.
         *
         *     A "negative value" (relative to zero_pt) in
         *     queue_info->idlers tells how many
         *     threads are waiting on an idle worker.
         */
        if (queue_info->idlers < zero_pt) {
            if (had_to_block) {
                *had_to_block = 1;
            }
            rv = apr_thread_cond_wait(queue_info->wait_for_idler,
                                      queue_info->idlers_mutex);
            if (rv != APR_SUCCESS) {
                AP_DEBUG_ASSERT(0);
                apr_thread_mutex_unlock(queue_info->idlers_mutex);
                return rv;
            }
        }
        rv = apr_thread_mutex_unlock(queue_info->idlers_mutex);
        if (rv != APR_SUCCESS) {
            return rv;
        }
    }

    if (queue_info->terminated) {
        return APR_EOF;
    }
    else {
        return APR_SUCCESS;
    }
}

apr_uint32_t ap_queue_info_num_idlers(fd_queue_info_t *queue_info)
{
    apr_uint32_t val;
    val = apr_atomic_read32(&queue_info->idlers);
    return (val > zero_pt) ? val - zero_pt : 0;
}

void ap_queue_info_push_pool(fd_queue_info_t *queue_info,
                             apr_pool_t *pool_to_recycle)
{
    struct recycled_pool *new_recycle;
    /* If we have been given a pool to recycle, atomically link
     * it into the queue_info's list of recycled pools
     */
    if (!pool_to_recycle)
        return;

    if (queue_info->max_recycled_pools >= 0) {
        apr_uint32_t n = apr_atomic_read32(&queue_info->recycled_pools_count);
        if (n >= queue_info->max_recycled_pools) {
            apr_pool_destroy(pool_to_recycle);
            return;
        }
        apr_atomic_inc32(&queue_info->recycled_pools_count);
    }

    apr_pool_clear(pool_to_recycle);
    new_recycle = apr_palloc(pool_to_recycle, sizeof *new_recycle);
    new_recycle->pool = pool_to_recycle;
    for (;;) {
        /*
         * Save queue_info->recycled_pool in local variable next because
         * new_recycle->next can be changed after apr_atomic_casptr
         * function call. For gory details see PR 44402.
         */
        struct recycled_pool *next = queue_info->recycled_pools;
        new_recycle->next = next;
        if (apr_atomic_casptr((void *)&queue_info->recycled_pools,
                              new_recycle, next) == next)
            break;
    }
}

void ap_queue_info_pop_pool(fd_queue_info_t *queue_info,
                            apr_pool_t **recycled_pool)
{
    /* Atomically pop a pool from the recycled list */

    /* This function is safe only as long as it is single threaded because
     * it reaches into the queue and accesses "next" which can change.
     * We are OK today because it is only called from the listener thread.
     * cas-based pushes do not have the same limitation - any number can
     * happen concurrently with a single cas-based pop.
     */

    *recycled_pool = NULL;


    /* Atomically pop a pool from the recycled list */
    for (;;) {
        struct recycled_pool *first_pool = queue_info->recycled_pools;
        if (first_pool == NULL) {
            break;
        }
        if (apr_atomic_casptr((void *)&queue_info->recycled_pools,
                              first_pool->next, first_pool) == first_pool) {
            *recycled_pool = first_pool->pool;
            if (queue_info->max_recycled_pools >= 0)
                apr_atomic_dec32(&queue_info->recycled_pools_count);
            break;
        }
    }
}

void ap_queue_info_free_idle_pools(fd_queue_info_t *queue_info)
{
    apr_pool_t *p;

    queue_info->max_recycled_pools = 0;
    for (;;) {
        ap_queue_info_pop_pool(queue_info, &p);
        if (p == NULL)
            break;
        apr_pool_destroy(p);
    }
    apr_atomic_set32(&queue_info->recycled_pools_count, 0);
}


apr_status_t ap_queue_info_term(fd_queue_info_t *queue_info)
{
    apr_status_t rv;

    rv = apr_thread_mutex_lock(queue_info->idlers_mutex);
    if (rv != APR_SUCCESS) {
        return rv;
    }

    queue_info->terminated = 1;
    apr_thread_cond_broadcast(queue_info->wait_for_idler);

    return apr_thread_mutex_unlock(queue_info->idlers_mutex);
}

/**
 * Detects when the fd_queue_t is full. This utility function is expected
 * to be called from within critical sections, and is not threadsafe.
 */
#define ap_queue_full(queue) ((queue)->nelts == (queue)->bounds)

/**
 * Detects when the fd_queue_t is empty. This utility function is expected
 * to be called from within critical sections, and is not threadsafe.
 */
#define ap_queue_empty(queue) ((queue)->nelts == 0 && \
                               APR_RING_EMPTY(&queue->timers, \
                                              timer_event_t, link))

/**
 * Callback routine that is called to destroy this
 * fd_queue_t when its pool is destroyed.
 */
static apr_status_t ap_queue_destroy(void *data)
{
    fd_queue_t *queue = data;

    /* Ignore errors here, we can't do anything about them anyway.
     * XXX: We should at least try to signal an error here, it is
     * indicative of a programmer error. -aaron */
    apr_thread_cond_destroy(queue->not_empty);
    apr_thread_mutex_destroy(queue->one_big_mutex);

    return APR_SUCCESS;
}

/**
 * Initialize the fd_queue_t.
 */
apr_status_t ap_queue_create(fd_queue_t **pqueue, int capacity, apr_pool_t *p)
{
    apr_status_t rv;
    fd_queue_t *queue;

    queue = apr_pcalloc(p, sizeof *queue);

    if ((rv = apr_thread_mutex_create(&queue->one_big_mutex,
                                      APR_THREAD_MUTEX_DEFAULT,
                                      p)) != APR_SUCCESS) {
        return rv;
    }
    if ((rv = apr_thread_cond_create(&queue->not_empty, p)) != APR_SUCCESS) {
        return rv;
    }

    APR_RING_INIT(&queue->timers, timer_event_t, link);

    queue->data = apr_pcalloc(p, capacity * sizeof(fd_queue_elem_t));
    queue->bounds = capacity;

    apr_pool_cleanup_register(p, queue, ap_queue_destroy,
                              apr_pool_cleanup_null);
    *pqueue = queue;

    return APR_SUCCESS;
}

/**
 * Push a new socket onto the queue.
 *
 * precondition: ap_queue_info_wait_for_idler has already been called
 *               to reserve an idle worker thread
 */
apr_status_t ap_queue_push_socket(fd_queue_t *queue,
                                  apr_socket_t *sd, void *sd_baton,
                                  apr_pool_t *p)
{
    fd_queue_elem_t *elem;
    apr_status_t rv;

    if ((rv = apr_thread_mutex_lock(queue->one_big_mutex)) != APR_SUCCESS) {
        return rv;
    }

    AP_DEBUG_ASSERT(!queue->terminated);
    AP_DEBUG_ASSERT(!ap_queue_full(queue));

    elem = &queue->data[queue->in++];
    if (queue->in >= queue->bounds)
        queue->in -= queue->bounds;
    elem->sd = sd;
    elem->sd_baton = sd_baton;
    elem->p = p;
    queue->nelts++;

    apr_thread_cond_signal(queue->not_empty);

    return apr_thread_mutex_unlock(queue->one_big_mutex);
}

apr_status_t ap_queue_push_timer(fd_queue_t *queue, timer_event_t *te)
{
    apr_status_t rv;

    if ((rv = apr_thread_mutex_lock(queue->one_big_mutex)) != APR_SUCCESS) {
        return rv;
    }

    AP_DEBUG_ASSERT(!queue->terminated);

    APR_RING_INSERT_TAIL(&queue->timers, te, timer_event_t, link);

    apr_thread_cond_signal(queue->not_empty);

    return apr_thread_mutex_unlock(queue->one_big_mutex);
}

/**
 * Retrieves the next available socket from the queue. If there are no
 * sockets available, it will block until one becomes available.
 * Once retrieved, the socket is placed into the address specified by
 * 'sd'.
 */
apr_status_t ap_queue_pop_something(fd_queue_t *queue,
                                    apr_socket_t **sd, void **sd_baton,
                                    apr_pool_t **p, timer_event_t **te_out)
{
    fd_queue_elem_t *elem;
    timer_event_t *te;
    apr_status_t rv;

    if ((rv = apr_thread_mutex_lock(queue->one_big_mutex)) != APR_SUCCESS) {
        return rv;
    }

    /* Keep waiting until we wake up and find that the queue is not empty. */
    if (ap_queue_empty(queue)) {
        if (!queue->terminated) {
            apr_thread_cond_wait(queue->not_empty, queue->one_big_mutex);
        }
        /* If we wake up and it's still empty, then we were interrupted */
        if (ap_queue_empty(queue)) {
            rv = apr_thread_mutex_unlock(queue->one_big_mutex);
            if (rv != APR_SUCCESS) {
                return rv;
            }
            if (queue->terminated) {
                return APR_EOF; /* no more elements ever again */
            }
            else {
                return APR_EINTR;
            }
        }
    }

    te = NULL;
    if (te_out) {
        if (!APR_RING_EMPTY(&queue->timers, timer_event_t, link)) {
            te = APR_RING_FIRST(&queue->timers);
            APR_RING_REMOVE(te, link);
        }
        *te_out = te;
    }
    if (!te) {
        elem = &queue->data[queue->out++];
        if (queue->out >= queue->bounds)
            queue->out -= queue->bounds;
        queue->nelts--;

        *sd = elem->sd;
        if (sd_baton) {
            *sd_baton = elem->sd_baton;
        }
        *p = elem->p;
#ifdef AP_DEBUG
        elem->sd = NULL;
        elem->p = NULL;
#endif /* AP_DEBUG */
    }

    return apr_thread_mutex_unlock(queue->one_big_mutex);
}

static apr_status_t queue_interrupt(fd_queue_t *queue, int all, int term)
{
    apr_status_t rv;

    if (queue->terminated) {
        return APR_EOF;
    }

    if ((rv = apr_thread_mutex_lock(queue->one_big_mutex)) != APR_SUCCESS) {
        return rv;
    }

    /* we must hold one_big_mutex when setting this... otherwise,
     * we could end up setting it and waking everybody up just after a
     * would-be popper checks it but right before they block
     */
    if (term) {
        queue->terminated = 1;
    }
    if (all)
        apr_thread_cond_broadcast(queue->not_empty);
    else
        apr_thread_cond_signal(queue->not_empty);

    return apr_thread_mutex_unlock(queue->one_big_mutex);
}

apr_status_t ap_queue_interrupt_all(fd_queue_t *queue)
{
    return queue_interrupt(queue, 1, 0);
}

apr_status_t ap_queue_interrupt_one(fd_queue_t *queue)
{
    return queue_interrupt(queue, 0, 0);
}

apr_status_t ap_queue_term(fd_queue_t *queue)
{
    return queue_interrupt(queue, 1, 1);
}

#endif /* APR_HAS_THREADS */

Coverage Report

Created: 2023-03-26 06:28

Line	Count	Source (jump to first uncovered line)
1		/* Licensed to the Apache Software Foundation (ASF) under one or more
2		* contributor license agreements. See the NOTICE file distributed with
3		* this work for additional information regarding copyright ownership.
4		* The ASF licenses this file to You under the Apache License, Version 2.0
5		* (the "License"); you may not use this file except in compliance with
6		* the License. You may obtain a copy of the License at
7		*
8		* http://www.apache.org/licenses/LICENSE-2.0
9		*
10		* Unless required by applicable law or agreed to in writing, software
11		* distributed under the License is distributed on an "AS IS" BASIS,
12		* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13		* See the License for the specific language governing permissions and
14		* limitations under the License.
15		*/
16
17		#include "mpm_fdqueue.h"
18
19		#if APR_HAS_THREADS
20
21		#include <apr_atomic.h>
22
23		static const apr_uint32_t zero_pt = APR_UINT32_MAX/2;
24
25		struct recycled_pool
26		{
27		apr_pool_t *pool;
28		struct recycled_pool *next;
29		};
30
31		struct fd_queue_info_t
32		{
33		apr_uint32_t volatile idlers; /**
34		* >= zero_pt: number of idle worker threads
35		* < zero_pt: number of threads blocked,
36		* waiting for an idle worker
37		*/
38		apr_thread_mutex_t *idlers_mutex;
39		apr_thread_cond_t *wait_for_idler;
40		int terminated;
41		int max_idlers;
42		int max_recycled_pools;
43		apr_uint32_t recycled_pools_count;
44		struct recycled_pool *volatile recycled_pools;
45		};
46
47		struct fd_queue_elem_t
48		{
49		apr_socket_t *sd;
50		void *sd_baton;
51		apr_pool_t *p;
52		};
53
54		static apr_status_t queue_info_cleanup(void *data_)
55	0	{
56	0	fd_queue_info_t *qi = data_;
57	0	apr_thread_cond_destroy(qi->wait_for_idler);
58	0	apr_thread_mutex_destroy(qi->idlers_mutex);
59
60		/* Clean up any pools in the recycled list */
61	0	for (;;) {
62	0	struct recycled_pool *first_pool = qi->recycled_pools;
63	0	if (first_pool == NULL) {
64	0	break;
65	0	}
66	0	if (apr_atomic_casptr((void *)&qi->recycled_pools, first_pool->next,
67	0	first_pool) == first_pool) {
68	0	apr_pool_destroy(first_pool->pool);
69	0	}
70	0	}
71
72	0	return APR_SUCCESS;
73	0	}
74
75		apr_status_t ap_queue_info_create(fd_queue_info_t **queue_info,
76		apr_pool_t *pool, int max_idlers,
77		int max_recycled_pools)
78	0	{
79	0	apr_status_t rv;
80	0	fd_queue_info_t *qi;
81
82	0	qi = apr_pcalloc(pool, sizeof(*qi));
83
84	0	rv = apr_thread_mutex_create(&qi->idlers_mutex, APR_THREAD_MUTEX_DEFAULT,
85	0	pool);
86	0	if (rv != APR_SUCCESS) {
87	0	return rv;
88	0	}
89	0	rv = apr_thread_cond_create(&qi->wait_for_idler, pool);
90	0	if (rv != APR_SUCCESS) {
91	0	return rv;
92	0	}
93	0	qi->recycled_pools = NULL;
94	0	qi->max_recycled_pools = max_recycled_pools;
95	0	qi->max_idlers = max_idlers;
96	0	qi->idlers = zero_pt;
97	0	apr_pool_cleanup_register(pool, qi, queue_info_cleanup,
98	0	apr_pool_cleanup_null);
99
100	0	*queue_info = qi;
101
102	0	return APR_SUCCESS;
103	0	}
104
105		apr_status_t ap_queue_info_set_idle(fd_queue_info_t *queue_info,
106		apr_pool_t *pool_to_recycle)
107	0	{
108	0	apr_status_t rv;
109
110	0	ap_queue_info_push_pool(queue_info, pool_to_recycle);
111
112		/* If other threads are waiting on a worker, wake one up */
113	0	if (apr_atomic_inc32(&queue_info->idlers) < zero_pt) {
114	0	rv = apr_thread_mutex_lock(queue_info->idlers_mutex);
115	0	if (rv != APR_SUCCESS) {
116	0	AP_DEBUG_ASSERT(0);
117	0	return rv;
118	0	}
119	0	rv = apr_thread_cond_signal(queue_info->wait_for_idler);
120	0	if (rv != APR_SUCCESS) {
121	0	apr_thread_mutex_unlock(queue_info->idlers_mutex);
122	0	return rv;
123	0	}
124	0	rv = apr_thread_mutex_unlock(queue_info->idlers_mutex);
125	0	if (rv != APR_SUCCESS) {
126	0	return rv;
127	0	}
128	0	}
129
130	0	return APR_SUCCESS;
131	0	}
132
133		apr_status_t ap_queue_info_try_get_idler(fd_queue_info_t *queue_info)
134	0	{
135		/* Don't block if there isn't any idle worker. */
136	0	for (;;) {
137	0	apr_uint32_t idlers = queue_info->idlers;
138	0	if (idlers <= zero_pt) {
139	0	return APR_EAGAIN;
140	0	}
141	0	if (apr_atomic_cas32(&queue_info->idlers, idlers - 1,
142	0	idlers) == idlers) {
143	0	return APR_SUCCESS;
144	0	}
145	0	}
146	0	}
147
148		apr_status_t ap_queue_info_wait_for_idler(fd_queue_info_t *queue_info,
149		int *had_to_block)
150	0	{
151	0	apr_status_t rv;
152
153		/* Block if there isn't any idle worker.
154		* apr_atomic_add32(x, -1) does the same as dec32(x), except
155		* that it returns the previous value (unlike dec32's bool).
156		*/
157	0	if (apr_atomic_add32(&queue_info->idlers, -1) <= zero_pt) {
158	0	rv = apr_thread_mutex_lock(queue_info->idlers_mutex);
159	0	if (rv != APR_SUCCESS) {
160	0	AP_DEBUG_ASSERT(0);
161	0	apr_atomic_inc32(&(queue_info->idlers)); /* back out dec */
162	0	return rv;
163	0	}
164		/* Re-check the idle worker count to guard against a
165		* race condition. Now that we're in the mutex-protected
166		* region, one of two things may have happened:
167		* - If the idle worker count is still negative, the
168		* workers are all still busy, so it's safe to
169		* block on a condition variable.
170		* - If the idle worker count is non-negative, then a
171		* worker has become idle since the first check
172		* of queue_info->idlers above. It's possible
173		* that the worker has also signaled the condition
174		* variable--and if so, the listener missed it
175		* because it wasn't yet blocked on the condition
176		* variable. But if the idle worker count is
177		* now non-negative, it's safe for this function to
178		* return immediately.
179		*
180		* A "negative value" (relative to zero_pt) in
181		* queue_info->idlers tells how many
182		* threads are waiting on an idle worker.
183		*/
184	0	if (queue_info->idlers < zero_pt) {
185	0	if (had_to_block) {
186	0	*had_to_block = 1;
187	0	}
188	0	rv = apr_thread_cond_wait(queue_info->wait_for_idler,
189	0	queue_info->idlers_mutex);
190	0	if (rv != APR_SUCCESS) {
191	0	AP_DEBUG_ASSERT(0);
192	0	apr_thread_mutex_unlock(queue_info->idlers_mutex);
193	0	return rv;
194	0	}
195	0	}
196	0	rv = apr_thread_mutex_unlock(queue_info->idlers_mutex);
197	0	if (rv != APR_SUCCESS) {
198	0	return rv;
199	0	}
200	0	}
201
202	0	if (queue_info->terminated) {
203	0	return APR_EOF;
204	0	}
205	0	else {
206	0	return APR_SUCCESS;
207	0	}
208	0	}
209
210		apr_uint32_t ap_queue_info_num_idlers(fd_queue_info_t *queue_info)
211	0	{
212	0	apr_uint32_t val;
213	0	val = apr_atomic_read32(&queue_info->idlers);
214	0	return (val > zero_pt) ? val - zero_pt : 0;
215	0	}
216
217		void ap_queue_info_push_pool(fd_queue_info_t *queue_info,
218		apr_pool_t *pool_to_recycle)
219	0	{
220	0	struct recycled_pool *new_recycle;
221		/* If we have been given a pool to recycle, atomically link
222		* it into the queue_info's list of recycled pools
223		*/
224	0	if (!pool_to_recycle)
225	0	return;
226
227	0	if (queue_info->max_recycled_pools >= 0) {
228	0	apr_uint32_t n = apr_atomic_read32(&queue_info->recycled_pools_count);
229	0	if (n >= queue_info->max_recycled_pools) {
230	0	apr_pool_destroy(pool_to_recycle);
231	0	return;
232	0	}
233	0	apr_atomic_inc32(&queue_info->recycled_pools_count);
234	0	}
235
236	0	apr_pool_clear(pool_to_recycle);
237	0	new_recycle = apr_palloc(pool_to_recycle, sizeof *new_recycle);
238	0	new_recycle->pool = pool_to_recycle;
239	0	for (;;) {
240		/*
241		* Save queue_info->recycled_pool in local variable next because
242		* new_recycle->next can be changed after apr_atomic_casptr
243		* function call. For gory details see PR 44402.
244		*/
245	0	struct recycled_pool *next = queue_info->recycled_pools;
246	0	new_recycle->next = next;
247	0	if (apr_atomic_casptr((void *)&queue_info->recycled_pools,
248	0	new_recycle, next) == next)
249	0	break;
250	0	}
251	0	}
252
253		void ap_queue_info_pop_pool(fd_queue_info_t *queue_info,
254		apr_pool_t **recycled_pool)
255	0	{
256		/* Atomically pop a pool from the recycled list */
257
258		/* This function is safe only as long as it is single threaded because
259		* it reaches into the queue and accesses "next" which can change.
260		* We are OK today because it is only called from the listener thread.
261		* cas-based pushes do not have the same limitation - any number can
262		* happen concurrently with a single cas-based pop.
263		*/
264
265	0	*recycled_pool = NULL;
266
267
268		/* Atomically pop a pool from the recycled list */
269	0	for (;;) {
270	0	struct recycled_pool *first_pool = queue_info->recycled_pools;
271	0	if (first_pool == NULL) {
272	0	break;
273	0	}
274	0	if (apr_atomic_casptr((void *)&queue_info->recycled_pools,
275	0	first_pool->next, first_pool) == first_pool) {
276	0	*recycled_pool = first_pool->pool;
277	0	if (queue_info->max_recycled_pools >= 0)
278	0	apr_atomic_dec32(&queue_info->recycled_pools_count);
279	0	break;
280	0	}
281	0	}
282	0	}
283
284		void ap_queue_info_free_idle_pools(fd_queue_info_t *queue_info)
285	0	{
286	0	apr_pool_t *p;
287
288	0	queue_info->max_recycled_pools = 0;
289	0	for (;;) {
290	0	ap_queue_info_pop_pool(queue_info, &p);
291	0	if (p == NULL)
292	0	break;
293	0	apr_pool_destroy(p);
294	0	}
295	0	apr_atomic_set32(&queue_info->recycled_pools_count, 0);
296	0	}
297
298
299		apr_status_t ap_queue_info_term(fd_queue_info_t *queue_info)
300	0	{
301	0	apr_status_t rv;
302
303	0	rv = apr_thread_mutex_lock(queue_info->idlers_mutex);
304	0	if (rv != APR_SUCCESS) {
305	0	return rv;
306	0	}
307
308	0	queue_info->terminated = 1;
309	0	apr_thread_cond_broadcast(queue_info->wait_for_idler);
310
311	0	return apr_thread_mutex_unlock(queue_info->idlers_mutex);
312	0	}
313
314		/**
315		* Detects when the fd_queue_t is full. This utility function is expected
316		* to be called from within critical sections, and is not threadsafe.
317		*/
318		#define ap_queue_full(queue) ((queue)->nelts == (queue)->bounds)
319
320		/**
321		* Detects when the fd_queue_t is empty. This utility function is expected
322		* to be called from within critical sections, and is not threadsafe.
323		*/
324	0	#define ap_queue_empty(queue) ((queue)->nelts == 0 && \
325	0	APR_RING_EMPTY(&queue->timers, \
326	0	timer_event_t, link))
327
328		/**
329		* Callback routine that is called to destroy this
330		* fd_queue_t when its pool is destroyed.
331		*/
332		static apr_status_t ap_queue_destroy(void *data)
333	0	{
334	0	fd_queue_t *queue = data;
335
336		/* Ignore errors here, we can't do anything about them anyway.
337		* XXX: We should at least try to signal an error here, it is
338		* indicative of a programmer error. -aaron */
339	0	apr_thread_cond_destroy(queue->not_empty);
340	0	apr_thread_mutex_destroy(queue->one_big_mutex);
341
342	0	return APR_SUCCESS;
343	0	}
344
345		/**
346		* Initialize the fd_queue_t.
347		*/
348		apr_status_t ap_queue_create(fd_queue_t *pqueue, int capacity, apr_pool_t p)
349	0	{
350	0	apr_status_t rv;
351	0	fd_queue_t *queue;
352
353	0	queue = apr_pcalloc(p, sizeof *queue);
354
355	0	if ((rv = apr_thread_mutex_create(&queue->one_big_mutex,
356	0	APR_THREAD_MUTEX_DEFAULT,
357	0	p)) != APR_SUCCESS) {
358	0	return rv;
359	0	}
360	0	if ((rv = apr_thread_cond_create(&queue->not_empty, p)) != APR_SUCCESS) {
361	0	return rv;
362	0	}
363
364	0	APR_RING_INIT(&queue->timers, timer_event_t, link);
365
366	0	queue->data = apr_pcalloc(p, capacity * sizeof(fd_queue_elem_t));
367	0	queue->bounds = capacity;
368
369	0	apr_pool_cleanup_register(p, queue, ap_queue_destroy,
370	0	apr_pool_cleanup_null);
371	0	*pqueue = queue;
372
373	0	return APR_SUCCESS;
374	0	}
375
376		/**
377		* Push a new socket onto the queue.
378		*
379		* precondition: ap_queue_info_wait_for_idler has already been called
380		* to reserve an idle worker thread
381		*/
382		apr_status_t ap_queue_push_socket(fd_queue_t *queue,
383		apr_socket_t sd, void sd_baton,
384		apr_pool_t *p)
385	0	{
386	0	fd_queue_elem_t *elem;
387	0	apr_status_t rv;
388
389	0	if ((rv = apr_thread_mutex_lock(queue->one_big_mutex)) != APR_SUCCESS) {
390	0	return rv;
391	0	}
392
393	0	AP_DEBUG_ASSERT(!queue->terminated);
394	0	AP_DEBUG_ASSERT(!ap_queue_full(queue));
395
396	0	elem = &queue->data[queue->in++];
397	0	if (queue->in >= queue->bounds)
398	0	queue->in -= queue->bounds;
399	0	elem->sd = sd;
400	0	elem->sd_baton = sd_baton;
401	0	elem->p = p;
402	0	queue->nelts++;
403
404	0	apr_thread_cond_signal(queue->not_empty);
405
406	0	return apr_thread_mutex_unlock(queue->one_big_mutex);
407	0	}
408
409		apr_status_t ap_queue_push_timer(fd_queue_t queue, timer_event_t te)
410	0	{
411	0	apr_status_t rv;
412
413	0	if ((rv = apr_thread_mutex_lock(queue->one_big_mutex)) != APR_SUCCESS) {
414	0	return rv;
415	0	}
416
417	0	AP_DEBUG_ASSERT(!queue->terminated);
418
419	0	APR_RING_INSERT_TAIL(&queue->timers, te, timer_event_t, link);
420
421	0	apr_thread_cond_signal(queue->not_empty);
422
423	0	return apr_thread_mutex_unlock(queue->one_big_mutex);
424	0	}
425
426		/**
427		* Retrieves the next available socket from the queue. If there are no
428		* sockets available, it will block until one becomes available.
429		* Once retrieved, the socket is placed into the address specified by
430		* 'sd'.
431		*/
432		apr_status_t ap_queue_pop_something(fd_queue_t *queue,
433		apr_socket_t sd, void sd_baton,
434		apr_pool_t p, timer_event_t te_out)
435	0	{
436	0	fd_queue_elem_t *elem;
437	0	timer_event_t *te;
438	0	apr_status_t rv;
439
440	0	if ((rv = apr_thread_mutex_lock(queue->one_big_mutex)) != APR_SUCCESS) {
441	0	return rv;
442	0	}
443
444		/* Keep waiting until we wake up and find that the queue is not empty. */
445	0	if (ap_queue_empty(queue)) {
446	0	if (!queue->terminated) {
447	0	apr_thread_cond_wait(queue->not_empty, queue->one_big_mutex);
448	0	}
449		/* If we wake up and it's still empty, then we were interrupted */
450	0	if (ap_queue_empty(queue)) {
451	0	rv = apr_thread_mutex_unlock(queue->one_big_mutex);
452	0	if (rv != APR_SUCCESS) {
453	0	return rv;
454	0	}
455	0	if (queue->terminated) {
456	0	return APR_EOF; /* no more elements ever again */
457	0	}
458	0	else {
459	0	return APR_EINTR;
460	0	}
461	0	}
462	0	}
463
464	0	te = NULL;
465	0	if (te_out) {
466	0	if (!APR_RING_EMPTY(&queue->timers, timer_event_t, link)) {
467	0	te = APR_RING_FIRST(&queue->timers);
468	0	APR_RING_REMOVE(te, link);
469	0	}
470	0	*te_out = te;
471	0	}
472	0	if (!te) {
473	0	elem = &queue->data[queue->out++];
474	0	if (queue->out >= queue->bounds)
475	0	queue->out -= queue->bounds;
476	0	queue->nelts--;
477
478	0	*sd = elem->sd;
479	0	if (sd_baton) {
480	0	*sd_baton = elem->sd_baton;
481	0	}
482	0	*p = elem->p;
483		#ifdef AP_DEBUG
484		elem->sd = NULL;
485		elem->p = NULL;
486		#endif /* AP_DEBUG */
487	0	}
488
489	0	return apr_thread_mutex_unlock(queue->one_big_mutex);
490	0	}
491
492		static apr_status_t queue_interrupt(fd_queue_t *queue, int all, int term)
493	0	{
494	0	apr_status_t rv;
495
496	0	if (queue->terminated) {
497	0	return APR_EOF;
498	0	}
499
500	0	if ((rv = apr_thread_mutex_lock(queue->one_big_mutex)) != APR_SUCCESS) {
501	0	return rv;
502	0	}
503
504		/* we must hold one_big_mutex when setting this... otherwise,
505		* we could end up setting it and waking everybody up just after a
506		* would-be popper checks it but right before they block
507		*/
508	0	if (term) {
509	0	queue->terminated = 1;
510	0	}
511	0	if (all)
512	0	apr_thread_cond_broadcast(queue->not_empty);
513	0	else
514	0	apr_thread_cond_signal(queue->not_empty);
515
516	0	return apr_thread_mutex_unlock(queue->one_big_mutex);
517	0	}
518
519		apr_status_t ap_queue_interrupt_all(fd_queue_t *queue)
520	0	{
521	0	return queue_interrupt(queue, 1, 0);
522	0	}
523
524		apr_status_t ap_queue_interrupt_one(fd_queue_t *queue)
525	0	{
526	0	return queue_interrupt(queue, 0, 0);
527	0	}
528
529		apr_status_t ap_queue_term(fd_queue_t *queue)
530	0	{
531	0	return queue_interrupt(queue, 1, 1);
532	0	}
533
534		#endif /* APR_HAS_THREADS */