/*
* Unix SMB/CIFS implementation.
* thread pool implementation
* Copyright (C) Volker Lendecke 2009
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see .
*/
#include "replace.h"
#include "system/time.h"
#include "system/wait.h"
#include "system/threads.h"
#include "pthreadpool.h"
#include "lib/util/dlinklist.h"
#ifdef NDEBUG
#undef NDEBUG
#endif
#include
struct pthreadpool_job {
int id;
void (*fn)(void *private_data);
void *private_data;
};
struct pthreadpool {
/*
* List pthreadpools for fork safety
*/
struct pthreadpool *prev, *next;
/*
* Control access to this struct
*/
pthread_mutex_t mutex;
/*
* Threads waiting for work do so here
*/
pthread_cond_t condvar;
/*
* Array of jobs
*/
size_t jobs_array_len;
struct pthreadpool_job *jobs;
size_t head;
size_t num_jobs;
/*
* Indicate job completion
*/
int (*signal_fn)(int jobid,
void (*job_fn)(void *private_data),
void *job_fn_private_data,
void *private_data);
void *signal_fn_private_data;
/*
* indicator to worker threads that they should shut down
*/
bool shutdown;
/*
* maximum number of threads
*/
int max_threads;
/*
* Number of threads
*/
int num_threads;
/*
* Number of idle threads
*/
int num_idle;
/*
* Condition variable indicating that helper threads should
* quickly go away making way for fork() without anybody
* waiting on pool->condvar.
*/
pthread_cond_t *prefork_cond;
/*
* Waiting position for helper threads while fork is
* running. The forking thread will have locked it, and all
* idle helper threads will sit here until after the fork,
* where the forking thread will unlock it again.
*/
pthread_mutex_t fork_mutex;
};
static pthread_mutex_t pthreadpools_mutex = PTHREAD_MUTEX_INITIALIZER;
static struct pthreadpool *pthreadpools = NULL;
static pthread_once_t pthreadpool_atfork_initialized = PTHREAD_ONCE_INIT;
static void pthreadpool_prep_atfork(void);
/*
* Initialize a thread pool
*/
int pthreadpool_init(unsigned max_threads, struct pthreadpool **presult,
int (*signal_fn)(int jobid,
void (*job_fn)(void *private_data),
void *job_fn_private_data,
void *private_data),
void *signal_fn_private_data)
{
struct pthreadpool *pool;
int ret;
pool = (struct pthreadpool *)malloc(sizeof(struct pthreadpool));
if (pool == NULL) {
return ENOMEM;
}
pool->signal_fn = signal_fn;
pool->signal_fn_private_data = signal_fn_private_data;
pool->jobs_array_len = 4;
pool->jobs = calloc(
pool->jobs_array_len, sizeof(struct pthreadpool_job));
if (pool->jobs == NULL) {
free(pool);
return ENOMEM;
}
pool->head = pool->num_jobs = 0;
ret = pthread_mutex_init(&pool->mutex, NULL);
if (ret != 0) {
free(pool->jobs);
free(pool);
return ret;
}
ret = pthread_cond_init(&pool->condvar, NULL);
if (ret != 0) {
pthread_mutex_destroy(&pool->mutex);
free(pool->jobs);
free(pool);
return ret;
}
ret = pthread_mutex_init(&pool->fork_mutex, NULL);
if (ret != 0) {
pthread_cond_destroy(&pool->condvar);
pthread_mutex_destroy(&pool->mutex);
free(pool->jobs);
free(pool);
return ret;
}
pool->shutdown = false;
pool->num_threads = 0;
pool->max_threads = max_threads;
pool->num_idle = 0;
pool->prefork_cond = NULL;
ret = pthread_mutex_lock(&pthreadpools_mutex);
if (ret != 0) {
pthread_mutex_destroy(&pool->fork_mutex);
pthread_cond_destroy(&pool->condvar);
pthread_mutex_destroy(&pool->mutex);
free(pool->jobs);
free(pool);
return ret;
}
DLIST_ADD(pthreadpools, pool);
ret = pthread_mutex_unlock(&pthreadpools_mutex);
assert(ret == 0);
pthread_once(&pthreadpool_atfork_initialized, pthreadpool_prep_atfork);
*presult = pool;
return 0;
}
static void pthreadpool_prepare_pool(struct pthreadpool *pool)
{
int ret;
ret = pthread_mutex_lock(&pool->fork_mutex);
assert(ret == 0);
ret = pthread_mutex_lock(&pool->mutex);
assert(ret == 0);
while (pool->num_idle != 0) {
int num_idle = pool->num_idle;
pthread_cond_t prefork_cond;
ret = pthread_cond_init(&prefork_cond, NULL);
assert(ret == 0);
/*
* Push all idle threads off pool->condvar. In the
* child we can destroy the pool, which would result
* in undefined behaviour in the
* pthread_cond_destroy(pool->condvar). glibc just
* blocks here.
*/
pool->prefork_cond = &prefork_cond;
ret = pthread_cond_signal(&pool->condvar);
assert(ret == 0);
while (pool->num_idle == num_idle) {
ret = pthread_cond_wait(&prefork_cond, &pool->mutex);
assert(ret == 0);
}
pool->prefork_cond = NULL;
ret = pthread_cond_destroy(&prefork_cond);
assert(ret == 0);
}
/*
* Probably it's well-defined somewhere: What happens to
* condvars after a fork? The rationale of pthread_atfork only
* writes about mutexes. So better be safe than sorry and
* destroy/reinit pool->condvar across a fork.
*/
ret = pthread_cond_destroy(&pool->condvar);
assert(ret == 0);
}
static void pthreadpool_prepare(void)
{
int ret;
struct pthreadpool *pool;
ret = pthread_mutex_lock(&pthreadpools_mutex);
assert(ret == 0);
pool = pthreadpools;
while (pool != NULL) {
pthreadpool_prepare_pool(pool);
pool = pool->next;
}
}
static void pthreadpool_parent(void)
{
int ret;
struct pthreadpool *pool;
for (pool = DLIST_TAIL(pthreadpools);
pool != NULL;
pool = DLIST_PREV(pool)) {
ret = pthread_cond_init(&pool->condvar, NULL);
assert(ret == 0);
ret = pthread_mutex_unlock(&pool->mutex);
assert(ret == 0);
ret = pthread_mutex_unlock(&pool->fork_mutex);
assert(ret == 0);
}
ret = pthread_mutex_unlock(&pthreadpools_mutex);
assert(ret == 0);
}
static void pthreadpool_child(void)
{
int ret;
struct pthreadpool *pool;
for (pool = DLIST_TAIL(pthreadpools);
pool != NULL;
pool = DLIST_PREV(pool)) {
pool->num_threads = 0;
pool->num_idle = 0;
pool->head = 0;
pool->num_jobs = 0;
ret = pthread_cond_init(&pool->condvar, NULL);
assert(ret == 0);
ret = pthread_mutex_unlock(&pool->mutex);
assert(ret == 0);
ret = pthread_mutex_unlock(&pool->fork_mutex);
assert(ret == 0);
}
ret = pthread_mutex_unlock(&pthreadpools_mutex);
assert(ret == 0);
}
static void pthreadpool_prep_atfork(void)
{
pthread_atfork(pthreadpool_prepare, pthreadpool_parent,
pthreadpool_child);
}
static int pthreadpool_free(struct pthreadpool *pool)
{
int ret, ret1, ret2;
ret = pthread_mutex_lock(&pthreadpools_mutex);
if (ret != 0) {
return ret;
}
DLIST_REMOVE(pthreadpools, pool);
ret = pthread_mutex_unlock(&pthreadpools_mutex);
assert(ret == 0);
ret = pthread_mutex_destroy(&pool->mutex);
ret1 = pthread_cond_destroy(&pool->condvar);
ret2 = pthread_mutex_destroy(&pool->fork_mutex);
if (ret != 0) {
return ret;
}
if (ret1 != 0) {
return ret1;
}
if (ret2 != 0) {
return ret2;
}
free(pool->jobs);
free(pool);
return 0;
}
/*
* Destroy a thread pool. Wake up all idle threads for exit. The last
* one will free the pool.
*/
int pthreadpool_destroy(struct pthreadpool *pool)
{
int ret, ret1;
ret = pthread_mutex_lock(&pool->mutex);
if (ret != 0) {
return ret;
}
if (pool->shutdown) {
ret = pthread_mutex_unlock(&pool->mutex);
assert(ret == 0);
return EBUSY;
}
pool->shutdown = true;
if (pool->num_threads == 0) {
ret = pthread_mutex_unlock(&pool->mutex);
assert(ret == 0);
ret = pthreadpool_free(pool);
return ret;
}
/*
* We have active threads, tell them to finish.
*/
ret = pthread_cond_broadcast(&pool->condvar);
ret1 = pthread_mutex_unlock(&pool->mutex);
assert(ret1 == 0);
return ret;
}
/*
* Prepare for pthread_exit(), pool->mutex must be locked and will be
* unlocked here. This is a bit of a layering violation, but here we
* also take care of removing the pool if we're the last thread.
*/
static void pthreadpool_server_exit(struct pthreadpool *pool)
{
int ret;
bool free_it;
pool->num_threads -= 1;
free_it = (pool->shutdown && (pool->num_threads == 0));
ret = pthread_mutex_unlock(&pool->mutex);
assert(ret == 0);
if (free_it) {
pthreadpool_free(pool);
}
}
static bool pthreadpool_get_job(struct pthreadpool *p,
struct pthreadpool_job *job)
{
if (p->num_jobs == 0) {
return false;
}
*job = p->jobs[p->head];
p->head = (p->head+1) % p->jobs_array_len;
p->num_jobs -= 1;
return true;
}
static bool pthreadpool_put_job(struct pthreadpool *p,
int id,
void (*fn)(void *private_data),
void *private_data)
{
struct pthreadpool_job *job;
if (p->num_jobs == p->jobs_array_len) {
struct pthreadpool_job *tmp;
size_t new_len = p->jobs_array_len * 2;
tmp = realloc(
p->jobs, sizeof(struct pthreadpool_job) * new_len);
if (tmp == NULL) {
return false;
}
p->jobs = tmp;
/*
* We just doubled the jobs array. The array implements a FIFO
* queue with a modulo-based wraparound, so we have to memcpy
* the jobs that are logically at the queue end but physically
* before the queue head into the reallocated area. The new
* space starts at the current jobs_array_len, and we have to
* copy everything before the current head job into the new
* area.
*/
memcpy(&p->jobs[p->jobs_array_len], p->jobs,
sizeof(struct pthreadpool_job) * p->head);
p->jobs_array_len = new_len;
}
job = &p->jobs[(p->head + p->num_jobs) % p->jobs_array_len];
job->id = id;
job->fn = fn;
job->private_data = private_data;
p->num_jobs += 1;
return true;
}
static void pthreadpool_undo_put_job(struct pthreadpool *p)
{
p->num_jobs -= 1;
}
static void *pthreadpool_server(void *arg)
{
struct pthreadpool *pool = (struct pthreadpool *)arg;
int res;
res = pthread_mutex_lock(&pool->mutex);
if (res != 0) {
return NULL;
}
while (1) {
struct timespec ts;
struct pthreadpool_job job;
/*
* idle-wait at most 1 second. If nothing happens in that
* time, exit this thread.
*/
clock_gettime(CLOCK_REALTIME, &ts);
ts.tv_sec += 1;
while ((pool->num_jobs == 0) && !pool->shutdown) {
pool->num_idle += 1;
res = pthread_cond_timedwait(
&pool->condvar, &pool->mutex, &ts);
pool->num_idle -= 1;
if (pool->prefork_cond != NULL) {
/*
* Me must allow fork() to continue
* without anybody waiting on
* &pool->condvar. Tell
* pthreadpool_prepare_pool that we
* got that message.
*/
res = pthread_cond_signal(pool->prefork_cond);
assert(res == 0);
res = pthread_mutex_unlock(&pool->mutex);
assert(res == 0);
/*
* pthreadpool_prepare_pool has
* already locked this mutex across
* the fork. This makes us wait
* without sitting in a condvar.
*/
res = pthread_mutex_lock(&pool->fork_mutex);
assert(res == 0);
res = pthread_mutex_unlock(&pool->fork_mutex);
assert(res == 0);
res = pthread_mutex_lock(&pool->mutex);
assert(res == 0);
}
if (res == ETIMEDOUT) {
if (pool->num_jobs == 0) {
/*
* we timed out and still no work for
* us. Exit.
*/
pthreadpool_server_exit(pool);
return NULL;
}
break;
}
assert(res == 0);
}
if (pthreadpool_get_job(pool, &job)) {
int ret;
/*
* Do the work with the mutex unlocked
*/
res = pthread_mutex_unlock(&pool->mutex);
assert(res == 0);
job.fn(job.private_data);
ret = pool->signal_fn(job.id,
job.fn, job.private_data,
pool->signal_fn_private_data);
res = pthread_mutex_lock(&pool->mutex);
assert(res == 0);
if (ret != 0) {
pthreadpool_server_exit(pool);
return NULL;
}
}
if ((pool->num_jobs == 0) && pool->shutdown) {
/*
* No more work to do and we're asked to shut down, so
* exit
*/
pthreadpool_server_exit(pool);
return NULL;
}
}
}
static int pthreadpool_create_thread(struct pthreadpool *pool)
{
pthread_attr_t thread_attr;
pthread_t thread_id;
int res;
sigset_t mask, omask;
/*
* Create a new worker thread. It should not receive any signals.
*/
sigfillset(&mask);
res = pthread_attr_init(&thread_attr);
if (res != 0) {
return res;
}
res = pthread_attr_setdetachstate(
&thread_attr, PTHREAD_CREATE_DETACHED);
if (res != 0) {
pthread_attr_destroy(&thread_attr);
return res;
}
res = pthread_sigmask(SIG_BLOCK, &mask, &omask);
if (res != 0) {
pthread_attr_destroy(&thread_attr);
return res;
}
res = pthread_create(&thread_id, &thread_attr, pthreadpool_server,
(void *)pool);
assert(pthread_sigmask(SIG_SETMASK, &omask, NULL) == 0);
pthread_attr_destroy(&thread_attr);
if (res == 0) {
pool->num_threads += 1;
}
return res;
}
int pthreadpool_add_job(struct pthreadpool *pool, int job_id,
void (*fn)(void *private_data), void *private_data)
{
int res;
res = pthread_mutex_lock(&pool->mutex);
if (res != 0) {
return res;
}
if (pool->shutdown) {
/*
* Protect against the pool being shut down while
* trying to add a job
*/
res = pthread_mutex_unlock(&pool->mutex);
assert(res == 0);
return EINVAL;
}
/*
* Add job to the end of the queue
*/
if (!pthreadpool_put_job(pool, job_id, fn, private_data)) {
res = pthread_mutex_unlock(&pool->mutex);
assert(res == 0);
return ENOMEM;
}
if (pool->num_idle > 0) {
int unlock_res;
/*
* We have idle threads, wake one.
*/
res = pthread_cond_signal(&pool->condvar);
if (res != 0) {
pthreadpool_undo_put_job(pool);
}
unlock_res = pthread_mutex_unlock(&pool->mutex);
assert(unlock_res == 0);
return res;
}
if ((pool->max_threads != 0) &&
(pool->num_threads >= pool->max_threads)) {
/*
* No more new threads, we just queue the request
*/
res = pthread_mutex_unlock(&pool->mutex);
assert(res == 0);
return 0;
}
res = pthreadpool_create_thread(pool);
if (res == 0) {
res = pthread_mutex_unlock(&pool->mutex);
assert(res == 0);
return 0;
}
if (pool->num_threads != 0) {
/*
* At least one thread is still available, let
* that one run the queued job.
*/
res = pthread_mutex_unlock(&pool->mutex);
assert(res == 0);
return 0;
}
/*
* No thread could be created to run job, fallback to sync
* call.
*/
pthreadpool_undo_put_job(pool);
res = pthread_mutex_unlock(&pool->mutex);
assert(res == 0);
fn(private_data);
res = pool->signal_fn(job_id, fn, private_data,
pool->signal_fn_private_data);
return res;
}