lib: Add threadpool manager

This adds a threadpool manager component in the library that is used
in the IRMd and IPCPs. The threadpool manager now doesn't detach
threads but does a join when they exit. This solves a data race in the
previous implementation where some threads were not completely finished
upon release of some resources.

2 files changed, 267 insertions, 0 deletions

diff --git a/src/lib/CMakeLists.txt b/src/lib/CMakeLists.txt
index e08869b8..822c8c9b 100644
--- a/src/lib/CMakeLists.txt
+++ b/src/lib/CMakeLists.txt
@@ -59,6 +59,7 @@ set(SOURCE_FILES
   shm_rdrbuff.c
   sockets.c
   time_utils.c
+  tpm.c
   utils.c
   )
 
diff --git a/src/lib/tpm.c b/src/lib/tpm.c
new file mode 100644
index 00000000..8298eeb5
--- /dev/null
+++ b/src/lib/tpm.c
@@ -0,0 +1,266 @@
+/*
+ * Ouroboros - Copyright (C) 2016 - 2017
+ *
+ * Threadpool management
+ *
+ *    Dimitri Staessens <dimitri.staessens@ugent.be>
+ *    Sander Vrijders   <sander.vrijders@ugent.be>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * version 2.1 as published by the Free Software Foundation.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301 USA
+ */
+
+#include <ouroboros/config.h>
+#include <ouroboros/errno.h>
+#include <ouroboros/list.h>
+#include <ouroboros/time_utils.h>
+#include <ouroboros/tpm.h>
+
+#include <pthread.h>
+#include <stdlib.h>
+
+#define TPM_TIMEOUT 1000
+
+struct pthr_el {
+        struct list_head next;
+
+        bool             join;
+
+        pthread_t        thr;
+};
+
+enum tpm_state {
+        TPM_NULL = 0,
+        TPM_INIT,
+        TPM_RUNNING
+};
+
+struct {
+        size_t           min;
+        size_t           inc;
+        size_t           max;
+        size_t           cur;
+
+        void * (* func)(void *);
+
+        struct list_head pool;
+
+        enum tpm_state   state;
+
+        pthread_cond_t   cond;
+        pthread_mutex_t  lock;
+
+        pthread_t        mgr;
+} tpm;
+
+static void tpm_join(void)
+{
+        struct list_head * p;
+        struct list_head * h;
+
+        list_for_each_safe(p, h, &tpm.pool) {
+                struct pthr_el * e = list_entry(p, struct pthr_el, next);
+                if (tpm.state != TPM_RUNNING)
+                        while (!e->join)
+                                pthread_cond_wait(&tpm.cond, &tpm.lock);
+
+                if (e->join) {
+                        pthread_join(e->thr, NULL);
+                        list_del(&e->next);
+                        free(e);
+                }
+        }
+}
+
+static void * tpmgr(void * o)
+{
+        struct timespec dl;
+        struct timespec to = {(TPM_TIMEOUT / 1000),
+                              (TPM_TIMEOUT % 1000) * MILLION};
+        (void) o;
+
+        while (true) {
+                clock_gettime(PTHREAD_COND_CLOCK, &dl);
+                ts_add(&dl, &to, &dl);
+
+                pthread_mutex_lock(&tpm.lock);
+
+                tpm_join();
+
+                if (tpm.state != TPM_RUNNING) {
+                        tpm.max = 0;
+                        tpm_join();
+                        pthread_mutex_unlock(&tpm.lock);
+                        break;
+                }
+
+                if (tpm.cur < tpm.min) {
+                        tpm.max = tpm.inc;
+
+                        while (tpm.cur < tpm.max) {
+                                struct pthr_el * e = malloc(sizeof(*e));
+                                if (e == NULL)
+                                        break;
+
+                                e->join = false;
+
+                                if (pthread_create(&e->thr, NULL,
+                                                   tpm.func, NULL)) {
+                                        free(e);
+                                } else {
+                                        list_add(&e->next, &tpm.pool);
+                                        ++tpm.cur;
+                                }
+                        }
+                }
+
+                if (pthread_cond_timedwait(&tpm.cond, &tpm.lock, &dl)
+                    == ETIMEDOUT)
+                        if (tpm.cur > tpm.min )
+                                --tpm.max;
+
+                pthread_mutex_unlock(&tpm.lock);
+        }
+
+        return (void *) 0;
+}
+
+int tpm_init(size_t min,
+             size_t inc,
+             void * (* func)(void *))
+{
+        pthread_condattr_t cattr;
+
+        if (pthread_mutex_init(&tpm.lock, NULL))
+                goto fail_lock;
+
+        if (pthread_condattr_init(&cattr))
+                goto fail_cattr;
+
+#ifndef __APPLE__
+        pthread_condattr_setclock(&cattr, PTHREAD_COND_CLOCK);
+#endif
+        if (pthread_cond_init(&tpm.cond, &cattr))
+                goto fail_cond;
+
+        list_head_init(&tpm.pool);
+
+        pthread_condattr_destroy(&cattr);
+
+        tpm.state = TPM_INIT;
+        tpm.func  = func;
+        tpm.min   = min;
+        tpm.inc   = inc;
+        tpm.max   = 0;
+        tpm.cur   = 0;
+
+        return 0;
+
+ fail_cond:
+        pthread_condattr_destroy(&cattr);
+ fail_cattr:
+        pthread_mutex_destroy(&tpm.lock);
+ fail_lock:
+        return -1;
+}
+
+int tpm_start(void)
+{
+        pthread_mutex_lock(&tpm.lock);
+
+        if (pthread_create(&tpm.mgr, NULL, tpmgr, NULL)) {
+                pthread_mutex_unlock(&tpm.lock);
+                return -1;
+        }
+
+        tpm.state = TPM_RUNNING;
+
+        pthread_mutex_unlock(&tpm.lock);
+
+        return 0;
+}
+
+void tpm_stop(void)
+{
+        pthread_mutex_lock(&tpm.lock);
+
+        tpm.state = TPM_NULL;
+
+        pthread_mutex_unlock(&tpm.lock);
+}
+
+void tpm_fini(void)
+{
+        pthread_join(tpm.mgr, NULL);
+
+        pthread_mutex_destroy(&tpm.lock);
+        pthread_cond_destroy(&tpm.cond);
+}
+
+bool tpm_check(void)
+{
+        bool ret;
+
+        pthread_mutex_lock(&tpm.lock);
+
+        ret = tpm.cur > tpm.max;
+
+        pthread_mutex_unlock(&tpm.lock);
+
+        return ret;
+}
+
+void tpm_inc(void)
+{
+        pthread_mutex_lock(&tpm.lock);
+
+        ++tpm.cur;
+
+        pthread_mutex_unlock(&tpm.lock);
+}
+
+void tpm_dec(void)
+{
+        pthread_mutex_lock(&tpm.lock);
+
+        --tpm.cur;
+
+        pthread_cond_signal(&tpm.cond);
+
+        pthread_mutex_unlock(&tpm.lock);
+}
+
+void tpm_exit(void)
+{
+        struct list_head * p;
+        pthread_t          id;
+
+        id = pthread_self();
+
+        pthread_mutex_lock(&tpm.lock);
+
+        --tpm.cur;
+
+        list_for_each(p, &tpm.pool) {
+                struct pthr_el * e = list_entry(p, struct pthr_el, next);
+                if (e->thr == id) {
+                        e->join = true;
+                        break;
+                }
+        }
+
+        pthread_cond_signal(&tpm.cond);
+
+        pthread_mutex_unlock(&tpm.lock);
+}