/* 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.
*/
/* The purpose of this MPM is to fix the design flaws in the threaded * model. Because of the way that pthreads and mutex locks interact, * it is basically impossible to cleanly gracefully shutdown a child * process if multiple threads are all blocked in accept. This model * fixes those problems.
*/
#include <signal.h> #include <limits.h> /* for INT_MAX */
/* Limit on the total --- clients will be locked out if more servers than * this are needed. It is intended solely to keep the server from crashing * when things get out of hand. * * We keep a hard maximum number of servers, for two reasons --- first off, * in case something goes seriously wrong, we want to stop the fork bomb * short of actually crashing the machine we're running on by filling some * kernel table. Secondly, it keeps the size of the scoreboard file small * enough that we can read the whole thing without worrying too much about * the overhead.
*/ #ifndef DEFAULT_SERVER_LIMIT #define DEFAULT_SERVER_LIMIT 16 #endif
/* Admin can't tune ServerLimit beyond MAX_SERVER_LIMIT. We want * some sort of compile-time limit to help catch typos.
*/ #ifndef MAX_SERVER_LIMIT #define MAX_SERVER_LIMIT 20000 #endif
/* Limit on the threads per process. Clients will be locked out if more than * this * server_limit are needed. * * We keep this for one reason it keeps the size of the scoreboard file small * enough that we can read the whole thing without worrying too much about * the overhead.
*/ #ifndef DEFAULT_THREAD_LIMIT #define DEFAULT_THREAD_LIMIT 64 #endif
/* Admin can't tune ThreadLimit beyond MAX_THREAD_LIMIT. We want * some sort of compile-time limit to help catch typos.
*/ #ifndef MAX_THREAD_LIMIT #define MAX_THREAD_LIMIT 20000 #endif
/* data retained by worker across load/unload of the module * allocated on first call to pre-config hook; located on * subsequent calls to pre-config hook
*/ typedefstruct worker_retained_data {
ap_unixd_mpm_retained_data *mpm;
int first_server_limit; int first_thread_limit; int sick_child_detected; int maxclients_reported; int near_maxclients_reported; /* * The max child slot ever assigned, preserved across restarts. Necessary * to deal with MaxRequestWorkers changes across AP_SIG_GRACEFUL restarts. * We use this value to optimize routines that have to scan the entire * scoreboard.
*/ int max_daemons_limit; /* * idle_spawn_rate is the number of children that will be spawned on the * next maintenance cycle if there aren't enough idle servers. It is * maintained per listeners bucket, doubled up to MAX_SPAWN_RATE, and * reset only when a cycle goes by without the need to spawn.
*/ int *idle_spawn_rate; #ifndef MAX_SPAWN_RATE #define MAX_SPAWN_RATE (32) #endif int hold_off_on_exponential_spawning;
} worker_retained_data; static worker_retained_data *retained;
/* The structure used to pass unique initialization info to each thread */ typedefstruct { int pid; int tid; int sd;
} proc_info;
/* Structure used to pass information to the thread responsible for * creating the rest of the threads.
*/ typedefstruct {
apr_thread_t **threads;
apr_thread_t *listener; int child_num_arg;
apr_threadattr_t *threadattr;
} thread_starter;
/* The worker MPM respects a couple of runtime flags that can aid * in debugging. Setting the -DNO_DETACH flag will prevent the root process * from detaching from its controlling terminal. Additionally, setting * the -DONE_PROCESS flag (which implies -DNO_DETACH) will get you the * child_main loop running in the process which originally started up. * This gives you a pretty nice debugging environment. (You'll get a SIGHUP * early in standalone_main; just continue through. This is the server * trying to kill off any child processes which it might have lying * around --- Apache doesn't keep track of their pids, it just sends * SIGHUP to the process group, ignoring it in the root process. * Continue through and you'll be fine.).
*/
staticint one_process = 0;
#ifdef DEBUG_SIGSTOP int raise_sigstop_flags; #endif
static apr_pool_t *pconf; /* Pool for config stuff */ static apr_pool_t *pchild; /* Pool for httpd child stuff */ static apr_pool_t *pruntime; /* Pool for MPM threads stuff */
static pid_t ap_my_pid; /* Linux getpid() doesn't work except in main
thread. Use this instead */ static pid_t parent_pid; static apr_os_thread_t *listener_os_thread;
/* The LISTENER_SIGNAL signal will be sent from the main thread to the * listener thread to wake it up for graceful termination (what a child * process from an old generation does when the admin does "apachectl * graceful"). This signal will be blocked in all threads of a child * process except for the listener thread.
*/ #define LISTENER_SIGNAL SIGHUP
/* The WORKER_SIGNAL signal will be sent from the main thread to the * worker threads during an ungraceful restart or shutdown. * This ensures that on systems (i.e., Linux) where closing the worker * socket doesn't awake the worker thread when it is polling on the socket * (especially in apr_wait_for_io_or_timeout() when handling * Keep-Alive connections), close_worker_sockets() and join_workers() * still function in timely manner and allow ungraceful shutdowns to * proceed to completion. Otherwise join_workers() doesn't return * before the main process decides the child process is non-responsive * and sends a SIGKILL.
*/ #define WORKER_SIGNAL AP_SIG_GRACEFUL
/* An array of socket descriptors in use by each thread used to
* perform a non-graceful (forced) shutdown of the server. */ static apr_socket_t **worker_sockets;
staticvoid close_worker_sockets(void)
{ int i; for (i = 0; i < threads_per_child; i++) { if (worker_sockets[i]) {
apr_socket_close(worker_sockets[i]);
worker_sockets[i] = NULL;
}
}
}
/* Unblock the listener if it's poll()ing */ if (worker_pollset && listener_is_wakeable) {
apr_pollset_wakeup(worker_pollset);
}
/* unblock the listener if it's waiting for a worker */
ap_queue_info_term(worker_queue_info);
if (!listener_os_thread) { /* XXX there is an obscure path that this doesn't handle perfectly: * right after listener thread is created but before * listener_os_thread is set, the first worker thread hits an * error and starts graceful termination
*/ return;
} /* * we should just be able to "kill(ap_my_pid, LISTENER_SIGNAL)" on all * platforms and wake up the listener thread since it is the only thread * with SIGHUP unblocked, but that doesn't work on Linux
*/ #ifdef HAVE_PTHREAD_KILL
pthread_kill(*listener_os_thread, LISTENER_SIGNAL); #else
kill(ap_my_pid, LISTENER_SIGNAL); #endif
}
/* in case we weren't called from the listener thread, wake up the * listener thread
*/
wakeup_listener();
/* for ungraceful termination, let the workers exit now; * for graceful termination, the listener thread will notify the * workers to exit once it has stopped accepting new connections
*/ if (mode == ST_UNGRACEFUL) {
workers_may_exit = 1;
ap_queue_interrupt_all(worker_queue);
close_worker_sockets(); /* forcefully kill all current connections */
}
staticvoid worker_note_child_lost_slot(int slot, pid_t newpid)
{
ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, ap_server_conf, APLOGNO(00263) "pid %" APR_PID_T_FMT " taking over scoreboard slot from " "%" APR_PID_T_FMT "%s",
newpid,
ap_scoreboard_image->parent[slot].pid,
ap_scoreboard_image->parent[slot].quiescing ? " (quiescing)" : "");
ap_run_child_status(ap_server_conf,
ap_scoreboard_image->parent[slot].pid,
ap_scoreboard_image->parent[slot].generation,
slot, MPM_CHILD_LOST_SLOT); /* Don't forget about this exiting child process, or we * won't be able to kill it if it doesn't exit by the * time the server is shut down.
*/
ap_register_extra_mpm_process(ap_scoreboard_image->parent[slot].pid,
ap_scoreboard_image->parent[slot].generation);
}
/* requests_this_child has gone to zero or below. See if the admin coded "MaxConnectionsPerChild 0", and keep going in that case. Doing it this way
simplifies the hot path in worker_thread */ staticvoid check_infinite_requests(void)
{ if (ap_max_requests_per_child) {
signal_threads(ST_GRACEFUL);
} else {
requests_this_child = INT_MAX; /* keep going */
}
}
staticvoid dummy_signal_handler(int sig)
{ /* XXX If specifying SIG_IGN is guaranteed to unblock a syscall, * then we don't need this goofy function.
*/
}
staticvoid accept_mutex_error(constchar *func, apr_status_t rv, int process_slot)
{ int level = APLOG_EMERG;
if (ap_scoreboard_image->parent[process_slot].generation !=
ap_scoreboard_image->global->running_generation) {
level = APLOG_DEBUG; /* common to get these at restart time */
} elseif (requests_this_child == INT_MAX
|| ((requests_this_child == ap_max_requests_per_child)
&& ap_max_requests_per_child)) {
ap_log_error(APLOG_MARK, level, rv, ap_server_conf, APLOGNO(00272) "apr_proc_mutex_%s failed " "before this child process served any requests.",
func);
clean_child_exit(APEXIT_CHILDSICK);
}
ap_log_error(APLOG_MARK, level, rv, ap_server_conf, APLOGNO(00273) "apr_proc_mutex_%s failed. Attempting to " "shutdown process gracefully.", func);
signal_threads(ST_GRACEFUL);
}
staticvoid * APR_THREAD_FUNC listener_thread(apr_thread_t *thd, void * dummy)
{
proc_info * ti = dummy; int process_slot = ti->pid; void *csd = NULL;
apr_pool_t *ptrans = NULL; /* Pool for per-transaction stuff */
apr_status_t rv;
ap_listen_rec *lr = NULL; int have_idle_worker = 0; int last_poll_idx = 0;
free(ti);
/* Unblock the signal used to wake this thread up, and set a handler for * it.
*/
apr_signal(LISTENER_SIGNAL, dummy_signal_handler);
unblock_signal(LISTENER_SIGNAL);
/* TODO: Switch to a system where threads reuse the results from earlier
poll calls - manoj */ while (1) { /* TODO: requests_this_child should be synchronized - aaron */ if (requests_this_child <= 0) {
check_infinite_requests();
} if (listener_may_exit) break;
if (!have_idle_worker) {
rv = ap_queue_info_wait_for_idler(worker_queue_info, NULL); if (APR_STATUS_IS_EOF(rv)) { break; /* we've been signaled to die now */
} elseif (rv != APR_SUCCESS) {
ap_log_error(APLOG_MARK, APLOG_EMERG, rv, ap_server_conf, "apr_queue_info_wait failed. Attempting to " " shutdown process gracefully.");
signal_threads(ST_GRACEFUL); break;
}
have_idle_worker = 1;
}
if ((rv = SAFE_ACCEPT(apr_proc_mutex_lock(my_bucket->mutex)))
!= APR_SUCCESS) {
if (!listener_may_exit) {
accept_mutex_error("lock", rv, process_slot);
} break; /* skip the lock release */
}
if (!my_bucket->listeners->next) { /* Only one listener, so skip the poll */
lr = my_bucket->listeners;
} else { while (!listener_may_exit) {
apr_int32_t numdesc; const apr_pollfd_t *pdesc;
rv = apr_pollset_poll(worker_pollset, -1, &numdesc, &pdesc); if (rv != APR_SUCCESS) { if (APR_STATUS_IS_EINTR(rv)) { continue;
}
/* apr_pollset_poll() will only return errors in catastrophic
* circumstances. Let's try exiting gracefully, for now. */
ap_log_error(APLOG_MARK, APLOG_ERR, rv, ap_server_conf, APLOGNO(03137) "apr_pollset_poll: (listen)");
signal_threads(ST_GRACEFUL);
}
if (listener_may_exit) break;
/* We can always use pdesc[0], but sockets at position N * could end up completely starved of attention in a very * busy server. Therefore, we round-robin across the * returned set of descriptors. While it is possible that * the returned set of descriptors might flip around and * continue to starve some sockets, we happen to know the * internal pollset implementation retains ordering * stability of the sockets. Thus, the round-robin should * ensure that a socket will eventually be serviced.
*/ if (last_poll_idx >= numdesc)
last_poll_idx = 0;
/* Grab a listener record from the client_data of the poll * descriptor, and advance our saved index to round-robin * the next fetch. * * ### hmm... this descriptor might have POLLERR rather * ### than POLLIN
*/
lr = pdesc[last_poll_idx++].client_data; break;
} /* while */
} /* if/else */
if (!listener_may_exit) { /* the following pops a recycled ptrans pool off a stack */
ap_queue_info_pop_pool(worker_queue_info, &ptrans); if (ptrans == NULL) { /* we can't use a recycled transaction pool this time.
* create a new transaction pool */
apr_allocator_t *allocator;
apr_allocator_create(&allocator);
apr_allocator_max_free_set(allocator, ap_max_mem_free);
apr_pool_create_ex(&ptrans, pconf, NULL, allocator);
apr_allocator_owner_set(allocator, ptrans);
apr_pool_tag(ptrans, "transaction");
}
rv = lr->accept_func(&csd, lr, ptrans); /* later we trash rv and rely on csd to indicate success/failure */
AP_DEBUG_ASSERT(rv == APR_SUCCESS || !csd);
if (listener_may_exit) { break;
}
accept_mutex_error("unlock", rv, process_slot);
} if (csd != NULL) {
rv = ap_queue_push_socket(worker_queue, csd, NULL, ptrans); if (rv) { /* trash the connection; we couldn't queue the connected * socket to a worker
*/
apr_socket_close(csd);
ap_log_error(APLOG_MARK, APLOG_CRIT, rv, ap_server_conf, APLOGNO(03138) "ap_queue_push_socket failed");
} else {
have_idle_worker = 0;
}
}
} else { if ((rv = SAFE_ACCEPT(apr_proc_mutex_unlock(my_bucket->mutex)))
!= APR_SUCCESS) { int level = APLOG_EMERG;
if (ap_scoreboard_image->parent[process_slot].generation !=
ap_scoreboard_image->global->running_generation) {
level = APLOG_DEBUG; /* common to get these at restart time */
}
ap_log_error(APLOG_MARK, level, rv, ap_server_conf, APLOGNO(00274) "apr_proc_mutex_unlock failed. Attempting to " "shutdown process gracefully.");
signal_threads(ST_GRACEFUL);
} break;
}
}
/* wake up the main thread */
kill(ap_my_pid, SIGTERM);
apr_thread_exit(thd, APR_SUCCESS); return NULL;
}
/* XXX For ungraceful termination/restart, we definitely don't want to * wait for active connections to finish but we may want to wait * for idle workers to get out of the queue code and release mutexes, * since those mutexes are cleaned up pretty soon and some systems * may not react favorably (i.e., segfault) if operations are attempted * on cleaned-up mutexes.
*/ staticvoid * APR_THREAD_FUNC worker_thread(apr_thread_t *thd, void * dummy)
{
proc_info * ti = dummy; int process_slot = ti->pid; int thread_slot = ti->tid;
apr_socket_t *csd = NULL;
apr_bucket_alloc_t *bucket_alloc;
apr_pool_t *last_ptrans = NULL;
apr_pool_t *ptrans; /* Pool for per-transaction stuff */
apr_status_t rv; int is_idle = 0;
if (rv != APR_SUCCESS) { /* We get APR_EOF during a graceful shutdown once all the connections * accepted by this server process have been handled.
*/ if (APR_STATUS_IS_EOF(rv)) { break;
} /* We get APR_EINTR whenever ap_queue_pop_*() has been interrupted * from an explicit call to ap_queue_interrupt_all(). This allows * us to unblock threads stuck in ap_queue_pop_*() when a shutdown * is pending. * * If workers_may_exit is set and this is ungraceful termination/ * restart, we are bound to get an error on some systems (e.g., * AIX, which sanity-checks mutex operations) since the queue * may have already been cleaned up. Don't log the "error" if * workers_may_exit is set.
*/ elseif (APR_STATUS_IS_EINTR(rv)) { goto worker_pop;
} /* We got some other error. */ elseif (!workers_may_exit) {
ap_log_error(APLOG_MARK, APLOG_CRIT, rv, ap_server_conf, APLOGNO(03139) "ap_queue_pop_socket failed");
} continue;
}
is_idle = 0;
worker_sockets[thread_slot] = csd;
bucket_alloc = apr_bucket_alloc_create(ptrans);
process_socket(thd, ptrans, csd, process_slot, thread_slot, bucket_alloc);
worker_sockets[thread_slot] = NULL;
requests_this_child--;
apr_pool_clear(ptrans);
last_ptrans = ptrans;
}
my_info = (proc_info *)ap_malloc(sizeof(proc_info));
my_info->pid = my_child_num;
my_info->tid = -1; /* listener thread doesn't have a thread slot */
my_info->sd = 0;
rv = ap_thread_create(&ts->listener, thread_attr, listener_thread,
my_info, pruntime); if (rv != APR_SUCCESS) {
ap_log_error(APLOG_MARK, APLOG_ALERT, rv, ap_server_conf, APLOGNO(00275) "ap_thread_create: unable to create listener thread"); /* let the parent decide how bad this really is */
clean_child_exit(APEXIT_CHILDSICK);
}
apr_os_thread_get(&listener_os_thread, ts->listener);
}
staticvoid setup_threads_runtime(void)
{
ap_listen_rec *lr; int pollset_flags;
apr_status_t rv;
/* All threads (listener, workers) and synchronization objects (queues, * pollset, mutexes...) created here should have at least the lifetime of * the connections they handle (i.e. ptrans). We can't use this thread's * self pool because all these objects survive it, nor use pchild or pconf * directly because this starter thread races with other modules' runtime, * nor finally pchild (or subpool thereof) because it is killed explicitly * before pconf (thus connections/ptrans can live longer, which matters in * ONE_PROCESS mode). So this leaves us with a subpool of pconf, created * before any ptrans hence destroyed after.
*/
apr_pool_create(&pruntime, pconf);
apr_pool_tag(pruntime, "mpm_runtime");
/* We must create the fd queues before we start up the listener
* and worker threads. */
rv = ap_queue_create(&worker_queue, threads_per_child, pruntime); if (rv != APR_SUCCESS) {
ap_log_error(APLOG_MARK, APLOG_ALERT, rv, ap_server_conf, APLOGNO(03140) "ap_queue_create() failed");
clean_child_exit(APEXIT_CHILDFATAL);
}
/* Create the main pollset. When APR_POLLSET_WAKEABLE is asked we account * for the wakeup pipe explicitely with num_listensocks+1 because some * pollset implementations don't do it implicitely in APR.
*/
pollset_flags = APR_POLLSET_NOCOPY | APR_POLLSET_WAKEABLE;
rv = apr_pollset_create(&worker_pollset, num_listensocks + 1, pruntime,
pollset_flags); if (rv == APR_SUCCESS) {
listener_is_wakeable = 1;
} else {
pollset_flags &= ~APR_POLLSET_WAKEABLE;
rv = apr_pollset_create(&worker_pollset, num_listensocks, pruntime,
pollset_flags);
} if (rv != APR_SUCCESS) {
ap_log_error(APLOG_MARK, APLOG_EMERG, rv, ap_server_conf, APLOGNO(03285) "Couldn't create pollset in thread;" " check system or user limits"); /* let the parent decide how bad this really is */
clean_child_exit(APEXIT_CHILDSICK);
}
for (lr = my_bucket->listeners; lr != NULL; lr = lr->next) {
apr_pollfd_t *pfd = apr_pcalloc(pruntime, sizeof *pfd);
rv = apr_pollset_add(worker_pollset, pfd); if (rv != APR_SUCCESS) {
ap_log_error(APLOG_MARK, APLOG_EMERG, rv, ap_server_conf, APLOGNO(03286) "Couldn't create add listener to pollset;" " check system or user limits"); /* let the parent decide how bad this really is */
clean_child_exit(APEXIT_CHILDSICK);
}
/* XXX under some circumstances not understood, children can get stuck * in start_threads forever trying to take over slots which will * never be cleaned up; for now there is an APLOG_DEBUG message issued * every so often when this condition occurs
*/ staticvoid * APR_THREAD_FUNC start_threads(apr_thread_t *thd, void *dummy)
{
thread_starter *ts = dummy;
apr_thread_t **threads = ts->threads;
apr_threadattr_t *thread_attr = ts->threadattr; int my_child_num = ts->child_num_arg;
proc_info *my_info;
apr_status_t rv; int threads_created = 0; int listener_started = 0; int prev_threads_created; int loops, i;
loops = prev_threads_created = 0; while (1) { /* threads_per_child does not include the listener thread */ for (i = 0; i < threads_per_child; i++) { int status = ap_scoreboard_image->servers[my_child_num][i].status;
if (status != SERVER_GRACEFUL && status != SERVER_DEAD) { continue;
}
/* We are creating threads right now */
ap_update_child_status_from_indexes(my_child_num, i,
SERVER_STARTING, NULL); /* We let each thread update its own scoreboard entry. This is * done because it lets us deal with tid better.
*/
rv = ap_thread_create(&threads[i], thread_attr,
worker_thread, my_info, pruntime); if (rv != APR_SUCCESS) {
ap_log_error(APLOG_MARK, APLOG_ALERT, rv, ap_server_conf, APLOGNO(03142) "ap_thread_create: unable to create worker thread"); /* let the parent decide how bad this really is */
clean_child_exit(APEXIT_CHILDSICK);
}
threads_created++;
} /* Start the listener only when there are workers available */ if (!listener_started && threads_created) {
create_listener_thread(ts);
listener_started = 1;
} if (start_thread_may_exit || threads_created == threads_per_child) { break;
} /* wait for previous generation to clean up an entry */
apr_sleep(apr_time_from_sec(1));
++loops; if (loops % 120 == 0) { /* every couple of minutes */ if (prev_threads_created == threads_created) {
ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, ap_server_conf, "child %" APR_PID_T_FMT " isn't taking over " "slots very quickly (%d of %d)",
ap_my_pid, threads_created, threads_per_child);
}
prev_threads_created = threads_created;
}
}
/* What state should this child_main process be listed as in the * scoreboard...? * ap_update_child_status_from_indexes(my_child_num, i, SERVER_STARTING, * (request_rec *) NULL); * * This state should be listed separately in the scoreboard, in some kind * of process_status, not mixed in with the worker threads' status. * "life_status" is almost right, but it's in the worker's structure, and * the name could be clearer. gla
*/
apr_thread_exit(thd, APR_SUCCESS); return NULL;
}
staticvoid join_workers(apr_thread_t *listener, apr_thread_t **threads, int mode)
{ int i;
apr_status_t rv, thread_rv;
if (listener) { int iter;
/* deal with a rare timing window which affects waking up the * listener thread... if the signal sent to the listener thread * is delivered between the time it verifies that the * listener_may_exit flag is clear and the time it enters a * blocking syscall, the signal didn't do any good... work around * that by sleeping briefly and sending it again
*/
iter = 0; while (!dying) {
apr_sleep(apr_time_from_msec(500)); if (dying || ++iter > 10) { break;
} /* listener has not stopped accepting yet */
ap_log_error(APLOG_MARK, APLOG_TRACE1, 0, ap_server_conf, "listener has not stopped accepting yet (%d iter)", iter);
wakeup_listener();
} if (iter > 10) {
ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, ap_server_conf, APLOGNO(00276) "the listener thread didn't exit");
} else {
rv = apr_thread_join(&thread_rv, listener); if (rv != APR_SUCCESS) {
ap_log_error(APLOG_MARK, APLOG_CRIT, rv, ap_server_conf, APLOGNO(00277) "apr_thread_join: unable to join listener thread");
}
}
}
for (i = 0; i < threads_per_child; i++) { if (threads[i]) { /* if we ever created this thread */ if (mode != ST_GRACEFUL) { #ifdef HAVE_PTHREAD_KILL
apr_os_thread_t *worker_os_thread;
start_thread_may_exit = 1; /* tell it to give up in case it is still * trying to take over slots from a * previous generation
*/
rv = apr_thread_join(&thread_rv, start_thread_id); if (rv != APR_SUCCESS) {
ap_log_error(APLOG_MARK, APLOG_CRIT, rv, ap_server_conf, APLOGNO(00279) "apr_thread_join: unable to join the start " "thread");
}
}
staticvoid child_main(int child_num_arg, int child_bucket)
{
apr_thread_t **threads;
apr_status_t rv;
thread_starter *ts;
apr_threadattr_t *thread_attr;
apr_thread_t *start_thread_id; int i;
/* for benefit of any hooks that run as this child initializes */
retained->mpm->mpm_state = AP_MPMQ_STARTING;
/* Get a sub context for global allocations in this child, so that * we can have cleanups occur when the child exits.
*/
apr_pool_create(&pchild, pconf);
apr_pool_tag(pchild, "pchild");
#if AP_HAS_THREAD_LOCAL if (!one_process) {
apr_thread_t *thd = NULL; if ((rv = ap_thread_main_create(&thd, pchild))) {
ap_log_error(APLOG_MARK, APLOG_EMERG, rv, ap_server_conf, APLOGNO(10375) "Couldn't initialize child main thread");
clean_child_exit(APEXIT_CHILDFATAL);
}
} #endif
/* close unused listeners and pods */ for (i = 0; i < retained->mpm->num_buckets; i++) { if (i != child_bucket) {
ap_close_listeners_ex(all_buckets[i].listeners);
ap_mpm_podx_close(all_buckets[i].pod);
}
}
/*stuff to do before we switch id's, so we have permissions.*/
ap_reopen_scoreboard(pchild, NULL, 0);
/* done with init critical section */ if (ap_run_drop_privileges(pchild, ap_server_conf)) {
clean_child_exit(APEXIT_CHILDFATAL);
}
/* Just use the standard apr_setup_signal_thread to block all signals * from being received. The child processes no longer use signals for * any communication with the parent process. Let's also do this before * child_init() hooks are called and possibly create threads that * otherwise could "steal" (implicitly) MPM's signals.
*/
rv = apr_setup_signal_thread(); if (rv != APR_SUCCESS) {
ap_log_error(APLOG_MARK, APLOG_EMERG, rv, ap_server_conf, APLOGNO(00281) "Couldn't initialize signal thread");
clean_child_exit(APEXIT_CHILDFATAL);
}
ap_run_child_init(pchild, ap_server_conf);
if (ap_max_requests_per_child) {
requests_this_child = ap_max_requests_per_child;
} else { /* coding a value of zero means infinity */
requests_this_child = INT_MAX;
}
/* Setup threads */
/* Globals used by signal_threads() so to be initialized before */
setup_threads_runtime();
/* clear the storage; we may not create all our threads immediately, * and we want a 0 entry to indicate a thread which was not created
*/
threads = (apr_thread_t **)ap_calloc(1, sizeof(apr_thread_t *) * threads_per_child);
ts = (thread_starter *)apr_palloc(pchild, sizeof(*ts));
apr_threadattr_create(&thread_attr, pchild); /* 0 means PTHREAD_CREATE_JOINABLE */
apr_threadattr_detach_set(thread_attr, 0);
if (ap_thread_stacksize != 0) {
rv = apr_threadattr_stacksize_set(thread_attr, ap_thread_stacksize); if (rv != APR_SUCCESS && rv != APR_ENOTIMPL) {
ap_log_error(APLOG_MARK, APLOG_WARNING, rv, ap_server_conf, APLOGNO(02435) "WARNING: ThreadStackSize of %" APR_SIZE_T_FMT " is " "inappropriate, using default",
ap_thread_stacksize);
}
}
rv = ap_thread_create(&start_thread_id, thread_attr, start_threads,
ts, pchild); if (rv != APR_SUCCESS) {
ap_log_error(APLOG_MARK, APLOG_ALERT, rv, ap_server_conf, APLOGNO(00282) "ap_thread_create: unable to create worker thread"); /* let the parent decide how bad this really is */
clean_child_exit(APEXIT_CHILDSICK);
}
retained->mpm->mpm_state = AP_MPMQ_RUNNING;
/* If we are only running in one_process mode, we will want to
* still handle signals. */ if (one_process) { /* Block until we get a terminating signal. */
apr_signal_thread(check_signal); /* make sure the start thread has finished; signal_threads() * and join_workers() depend on that
*/ /* XXX join_start_thread() won't be awakened if one of our * threads encounters a critical error and attempts to * shutdown this child
*/
join_start_thread(start_thread_id);
signal_threads(ST_UNGRACEFUL); /* helps us terminate a little more * quickly than the dispatch of the signal thread * beats the Pipe of Death and the browsers
*/ /* A terminating signal was received. Now join each of the * workers to clean them up. * If the worker already exited, then the join frees * their resources and returns. * If the worker hasn't exited, then this blocks until * they have (then cleans up).
*/
join_workers(ts->listener, threads, ST_UNGRACEFUL);
} else { /* !one_process */ /* remove SIGTERM from the set of blocked signals... if one of * the other threads in the process needs to take us down * (e.g., for MaxConnectionsPerChild) it will send us SIGTERM
*/
apr_signal(SIGTERM, dummy_signal_handler);
unblock_signal(SIGTERM); /* Watch for any messages from the parent over the POD */ while (1) {
rv = ap_mpm_podx_check(my_bucket->pod); if (rv == AP_MPM_PODX_NORESTART) { /* see if termination was triggered while we slept */ switch(terminate_mode) { case ST_GRACEFUL:
rv = AP_MPM_PODX_GRACEFUL; break; case ST_UNGRACEFUL:
rv = AP_MPM_PODX_RESTART; break;
}
} if (rv == AP_MPM_PODX_GRACEFUL || rv == AP_MPM_PODX_RESTART) { /* make sure the start thread has finished; * signal_threads() and join_workers depend on that
*/
join_start_thread(start_thread_id);
signal_threads(rv == AP_MPM_PODX_GRACEFUL ? ST_GRACEFUL : ST_UNGRACEFUL); break;
}
}
/* A terminating signal was received. Now join each of the * workers to clean them up. * If the worker already exited, then the join frees * their resources and returns. * If the worker hasn't exited, then this blocks until * they have (then cleans up).
*/
join_workers(ts->listener, threads,
rv == AP_MPM_PODX_GRACEFUL ? ST_GRACEFUL : ST_UNGRACEFUL);
}
if ((pid = fork()) == -1) {
ap_log_error(APLOG_MARK, APLOG_ERR, errno, s, APLOGNO(00283) "fork: Unable to fork new process"); /* fork didn't succeed. There's no need to touch the scoreboard; * if we were trying to replace a failed child process, then * server_main_loop() marked its workers SERVER_DEAD, and if * we were trying to replace a child process that exited normally, * its worker_thread()s left SERVER_DEAD or SERVER_GRACEFUL behind.
*/
/* In case system resources are maxxed out, we don't want Apache running away with the CPU trying to fork over and
over and over again. */
apr_sleep(apr_time_from_sec(10));
return -1;
}
if (!pid) { #if AP_HAS_THREAD_LOCAL
ap_thread_current_after_fork(); #endif
my_bucket = &all_buckets[bucket];
#ifdef HAVE_BINDPROCESSOR /* By default, AIX binds to a single processor. This bit unbinds * children which will then bind to another CPU.
*/ int status = bindprocessor(BINDPROCESS, (int)getpid(),
PROCESSOR_CLASS_ANY); if (status != OK)
ap_log_error(APLOG_MARK, APLOG_DEBUG, errno,
ap_server_conf, APLOGNO(00284) "processor unbind failed"); #endif
RAISE_SIGSTOP(MAKE_CHILD);
if (ap_scoreboard_image->parent[slot].pid != 0) { /* This new child process is squatting on the scoreboard * entry owned by an exiting child process, which cannot * exit until all active requests complete.
*/
worker_note_child_lost_slot(slot, pid);
}
ap_scoreboard_image->parent[slot].quiescing = 0;
worker_note_child_started(slot, pid); return 0;
}
/* start up a bunch of children */ staticvoid startup_children(int number_to_start)
{ int i;
for (i = 0; number_to_start && i < ap_daemons_limit; ++i) { if (ap_scoreboard_image->parent[i].pid != 0) { continue;
} if (make_child(ap_server_conf, i, i % retained->mpm->num_buckets) < 0) { break;
}
--number_to_start;
}
}
staticvoid perform_idle_server_maintenance(int child_bucket)
{ int num_buckets = retained->mpm->num_buckets; int idle_thread_count;
process_score *ps; int free_length; int totally_free_length = 0; int free_slots[MAX_SPAWN_RATE]; int last_non_dead; int total_non_dead; int active_thread_count = 0; int i, j;
for (i = 0; i < ap_daemons_limit; ++i) { /* Initialization to satisfy the compiler. It doesn't know
* that threads_per_child is always > 0 */ int any_dying_threads = 0; int any_dead_threads = 0; int all_dead_threads = 1; int child_threads_active = 0;
if (num_buckets > 1 && (i % num_buckets) != child_bucket) { /* We only care about child_bucket in this call */ continue;
} if (i >= retained->max_daemons_limit &&
totally_free_length == retained->idle_spawn_rate[child_bucket]) { /* short cut if all active processes have been examined and * enough empty scoreboard slots have been found
*/ break;
}
ps = &ap_scoreboard_image->parent[i]; for (j = 0; j < threads_per_child; j++) { int status = ap_scoreboard_image->servers[i][j].status;
/* We consider a starting server as idle because we started it * at least a cycle ago, and if it still hasn't finished starting * then we're just going to swamp things worse by forking more. * So we hopefully won't need to fork more if we count it. * This depends on the ordering of SERVER_READY and SERVER_STARTING.
*/ if (ps->pid != 0) { /* XXX just set all_dead_threads in outer for
loop if no pid? not much else matters */ if (status <= SERVER_READY &&
!ps->quiescing &&
ps->generation == retained->mpm->my_generation) {
++idle_thread_count;
} if (status >= SERVER_READY && status < SERVER_GRACEFUL) {
++child_threads_active;
}
}
}
active_thread_count += child_threads_active; if (any_dead_threads
&& totally_free_length < retained->idle_spawn_rate[child_bucket]
&& free_length < MAX_SPAWN_RATE / num_buckets
&& (!ps->pid /* no process in the slot */
|| ps->quiescing)) { /* or at least one is going away */ if (all_dead_threads) { /* great! we prefer these, because the new process can * start more threads sooner. So prioritize this slot * by putting it ahead of any slots with active threads. * * first, make room by moving a slot that's potentially still * in use to the end of the array
*/
free_slots[free_length] = free_slots[totally_free_length];
free_slots[totally_free_length++] = i;
} else { /* slot is still in use - back of the bus
*/
free_slots[free_length] = i;
}
++free_length;
} elseif (child_threads_active == threads_per_child) {
had_healthy_child = 1;
} /* XXX if (!ps->quiescing) is probably more reliable GLA */ if (!any_dying_threads) {
++total_non_dead;
} if (ps->pid != 0) {
last_non_dead = i;
}
}
retained->max_daemons_limit = last_non_dead + 1;
if (retained->sick_child_detected) { if (had_healthy_child) { /* Assume this is a transient error, even though it may not be. Leave * the server up in case it is able to serve some requests or the * problem will be resolved.
*/
retained->sick_child_detected = 0;
} elseif (child_bucket < num_buckets - 1) { /* check for had_healthy_child up to the last child bucket */ return;
} else { /* looks like a basket case, as no child ever fully initialized; give up.
*/
retained->mpm->shutdown_pending = 1;
child_fatal = 1;
ap_log_error(APLOG_MARK, APLOG_ALERT, 0,
ap_server_conf, APLOGNO(02325) "A resource shortage or other unrecoverable failure " "was encountered before any child process initialized " "successfully... httpd is exiting!"); /* the child already logged the failure details */ return;
}
}
if (idle_thread_count > max_spare_threads / num_buckets) { /* Kill off one child */
ap_mpm_podx_signal(all_buckets[child_bucket].pod,
AP_MPM_PODX_GRACEFUL);
retained->idle_spawn_rate[child_bucket] = 1;
} elseif (idle_thread_count < min_spare_threads / num_buckets) { /* terminate the free list */ if (free_length == 0) { /* scoreboard is full, can't fork */
if (active_thread_count >= max_workers / num_buckets) { /* no threads are "inactive" - starting, stopping, etc. */ /* have we reached MaxRequestWorkers, or just getting close? */ if (0 == idle_thread_count) { if (!retained->maxclients_reported) { /* only report this condition once */
ap_log_error(APLOG_MARK, APLOG_ERR, 0, ap_server_conf, APLOGNO(00286) "server reached MaxRequestWorkers " "setting, consider raising the " "MaxRequestWorkers setting");
retained->maxclients_reported = 1;
}
} else { if (!retained->near_maxclients_reported) {
ap_log_error(APLOG_MARK, APLOG_ERR, 0, ap_server_conf, APLOGNO(00287) "server is within MinSpareThreads of " "MaxRequestWorkers, consider raising the " "MaxRequestWorkers setting");
retained->near_maxclients_reported = 1;
}
}
} else {
ap_log_error(APLOG_MARK, APLOG_ERR, 0,
ap_server_conf, APLOGNO(00288) "scoreboard is full, not at MaxRequestWorkers");
}
retained->idle_spawn_rate[child_bucket] = 1;
} else { if (free_length > retained->idle_spawn_rate[child_bucket]) {
free_length = retained->idle_spawn_rate[child_bucket];
} if (retained->idle_spawn_rate[child_bucket] >= 8) {
ap_log_error(APLOG_MARK, APLOG_INFO, 0,
ap_server_conf, APLOGNO(00289) "server seems busy, (you may need " "to increase StartServers, ThreadsPerChild " "or Min/MaxSpareThreads), " "spawning %d children, there are around %d idle " "threads, and %d total children", free_length,
idle_thread_count, total_non_dead);
} for (i = 0; i < free_length; ++i) {
make_child(ap_server_conf, free_slots[i], child_bucket);
} /* the next time around we want to spawn twice as many if this * wasn't good enough, but not if we've just done a graceful
*/ if (retained->hold_off_on_exponential_spawning) {
--retained->hold_off_on_exponential_spawning;
} elseif (retained->idle_spawn_rate[child_bucket]
< MAX_SPAWN_RATE / num_buckets) {
retained->idle_spawn_rate[child_bucket] *= 2;
}
}
} else {
retained->idle_spawn_rate[child_bucket] = 1;
}
}
staticvoid server_main_loop(int remaining_children_to_start)
{ int num_buckets = retained->mpm->num_buckets; int successive_kills = 0;
ap_generation_t old_gen; int child_slot;
apr_exit_why_e exitwhy; int status, processed_status;
apr_proc_t pid; int i;
while (!retained->mpm->restart_pending && !retained->mpm->shutdown_pending) {
ap_wait_or_timeout(&exitwhy, &status, &pid, pconf, ap_server_conf);
if (pid.pid != -1) {
processed_status = ap_process_child_status(&pid, exitwhy, status);
child_slot = ap_find_child_by_pid(&pid); if (processed_status == APEXIT_CHILDFATAL) { /* fix race condition found in PR 39311 * A child created at the same time as a graceful happens * can find the lock missing and create a fatal error. * It is not fatal for the last generation to be in this state.
*/ if (child_slot < 0
|| ap_get_scoreboard_process(child_slot)->generation
== retained->mpm->my_generation) {
retained->mpm->shutdown_pending = 1;
child_fatal = 1; return;
} else {
ap_log_error(APLOG_MARK, APLOG_WARNING, 0, ap_server_conf, APLOGNO(00290) "Ignoring fatal error in child of previous " "generation (pid %ld).",
(long)pid.pid);
retained->sick_child_detected = 1;
}
} elseif (processed_status == APEXIT_CHILDSICK) { /* tell perform_idle_server_maintenance to check into this * on the next timer pop
*/
retained->sick_child_detected = 1;
} /* non-fatal death... note that it's gone in the scoreboard. */ if (child_slot >= 0) {
process_score *ps;
for (i = 0; i < threads_per_child; i++)
ap_update_child_status_from_indexes(child_slot, i,
SERVER_DEAD, NULL);
worker_note_child_killed(child_slot, 0, 0);
ps = &ap_scoreboard_image->parent[child_slot];
ps->quiescing = 0; if (processed_status == APEXIT_CHILDSICK) { /* resource shortage, minimize the fork rate */
retained->idle_spawn_rate[child_slot % num_buckets] = 1;
} elseif (remaining_children_to_start
&& child_slot < ap_daemons_limit) { /* we're still doing a 1-for-1 replacement of dead * children with new children
*/
make_child(ap_server_conf, child_slot,
child_slot % num_buckets);
--remaining_children_to_start;
}
} elseif (ap_unregister_extra_mpm_process(pid.pid, &old_gen) == 1) {
worker_note_child_killed(-1, /* already out of the scoreboard */
pid.pid, old_gen); if (processed_status == APEXIT_CHILDSICK
&& old_gen == retained->mpm->my_generation) { /* resource shortage, minimize the fork rate */ for (i = 0; i < num_buckets; i++) {
retained->idle_spawn_rate[i] = 1;
}
} #if APR_HAS_OTHER_CHILD
} elseif (apr_proc_other_child_alert(&pid, APR_OC_REASON_DEATH,
status) == 0) { /* handled */ #endif
} elseif (retained->mpm->was_graceful) { /* Great, we've probably just lost a slot in the * scoreboard. Somehow we don't know about this child.
*/
ap_log_error(APLOG_MARK, APLOG_WARNING, 0,
ap_server_conf, APLOGNO(00291) "long lost child came home! (pid %ld)",
(long)pid.pid);
} /* Don't perform idle maintenance when a child dies, * only do it when there's a timeout. Remember only a * finite number of children can die, and it's pretty * pathological for a lot to die suddenly. If a child is * killed by a signal (faulting) we want to restart it ASAP * though, up to 3 successive faults or we stop this until * a timeout happens again (to avoid the flood of fork()ed * processes that keep being killed early).
*/ if (child_slot < 0 || !APR_PROC_CHECK_SIGNALED(exitwhy)) { continue;
} if (++successive_kills >= 3) { if (successive_kills % 10 == 3) {
ap_log_error(APLOG_MARK, APLOG_WARNING, 0,
ap_server_conf, APLOGNO(10393) "children are killed successively!");
} continue;
}
++remaining_children_to_start;
} else {
successive_kills = 0;
}
if (remaining_children_to_start) { /* we hit a 1 second timeout in which none of the previous * generation of children needed to be reaped... so assume * they're all done, and pick up the slack if any is left.
*/
startup_children(remaining_children_to_start);
remaining_children_to_start = 0; /* In any event we really shouldn't do the code below because * few of the servers we just started are in the IDLE state * yet, so we'd mistakenly create an extra server.
*/ continue;
}
for (i = 0; i < num_buckets; i++) {
perform_idle_server_maintenance(i);
}
}
}
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