Adding upstream version 2.4.38.upstream/2.4.38upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 530 insertions, 0 deletions

diff --git a/server/mpm_fdqueue.c b/server/mpm_fdqueue.c
new file mode 100644
index 0000000..c812450
--- /dev/null
+++ b/server/mpm_fdqueue.c
@@ -0,0 +1,530 @@
+/* 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 ((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 */