src/bin/lttng-sessiond/thread.c

   1 /*
   2  * Copyright (C) 2018 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   3  *
   4  * SPDX-License-Identifier: GPL-2.0-only
   5  *
   6  */
   7
   8 #include "thread.h"
   9 #include <urcu/list.h>
  10 #include <urcu/ref.h>
  11 #include <pthread.h>
  12 #include <common/macros.h>
  13 #include <common/error.h>
  14 #include <common/defaults.h>
  15
  16 static struct thread_list {
  17         struct cds_list_head head;
  18         pthread_mutex_t lock;
  19 } thread_list = {
  20         .head = CDS_LIST_HEAD_INIT(thread_list.head),
  21         .lock = PTHREAD_MUTEX_INITIALIZER,
  22 };
  23
  24 struct lttng_thread {
  25         struct urcu_ref ref;
  26         struct cds_list_head node;
  27         pthread_t thread;
  28         const char *name;
  29         /* Main thread function */
  30         lttng_thread_entry_point entry;
  31         /*
  32          * Thread-specific shutdown method. Allows threads to implement their
  33          * own shutdown mechanism as some of them use a structured message
  34          * passed through a command queue and some rely on a dedicated "quit"
  35          * pipe.
  36          */
  37         lttng_thread_shutdown_cb shutdown;
  38         lttng_thread_cleanup_cb cleanup;
  39         /* Thread implementation-specific data. */
  40         void *data;
  41 };
  42
  43 static
  44 void lttng_thread_destroy(struct lttng_thread *thread)
  45 {
  46         if (thread->cleanup) {
  47                 thread->cleanup(thread->data);
  48         }
  49         free(thread);
  50 }
  51
  52 static
  53 void lttng_thread_release(struct urcu_ref *ref)
  54 {
  55         lttng_thread_destroy(container_of(ref, struct lttng_thread, ref));
  56 }
  57
  58 static
  59 void *launch_thread(void *data)
  60 {
  61         void *ret;
  62         struct lttng_thread *thread = (struct lttng_thread *) data;
  63
  64         logger_set_thread_name(thread->name, true);
  65         DBG("Entering thread entry point");
  66         ret = thread->entry(thread->data);
  67         DBG("Thread entry point has returned");
  68         return ret;
  69 }
  70
  71 struct lttng_thread *lttng_thread_create(const char *name,
  72                 lttng_thread_entry_point entry,
  73                 lttng_thread_shutdown_cb shutdown,
  74                 lttng_thread_cleanup_cb cleanup,
  75                 void *thread_data)
  76 {
  77         int ret;
  78         struct lttng_thread *thread;
  79
  80         thread = zmalloc(sizeof(*thread));
  81         if (!thread) {
  82                 goto error_alloc;
  83         }
  84
  85         urcu_ref_init(&thread->ref);
  86         CDS_INIT_LIST_HEAD(&thread->node);
  87         /*
  88          * Thread names are assumed to be statically allocated strings.
  89          * It is unnecessary to copy this attribute.
  90          */
  91         thread->name = name;
  92         thread->entry = entry;
  93         thread->shutdown = shutdown;
  94         thread->cleanup = cleanup;
  95         thread->data = thread_data;
  96
  97         pthread_mutex_lock(&thread_list.lock);
  98         /*
  99          * Add the thread at the head of the list to shutdown threads in the
 100          * opposite order of their creation. A reference is taken for the
 101          * thread list which will be released on shutdown of the thread.
 102          */
 103         cds_list_add(&thread->node, &thread_list.head);
 104         (void) lttng_thread_get(thread);
 105
 106         ret = pthread_create(&thread->thread, default_pthread_attr(),
 107                         launch_thread, thread);
 108         if (ret) {
 109                 PERROR("Failed to create \"%s\" thread", thread->name);
 110                 goto error_pthread_create;
 111         }
 112
 113         pthread_mutex_unlock(&thread_list.lock);
 114         return thread;
 115
 116 error_pthread_create:
 117         cds_list_del(&thread->node);
 118         /* Release list reference. */
 119         lttng_thread_put(thread);
 120         pthread_mutex_unlock(&thread_list.lock);
 121         /* Release initial reference. */
 122         lttng_thread_put(thread);
 123 error_alloc:
 124         return NULL;
 125 }
 126
 127 bool lttng_thread_get(struct lttng_thread *thread)
 128 {
 129         return urcu_ref_get_unless_zero(&thread->ref);
 130 }
 131
 132 void lttng_thread_put(struct lttng_thread *thread)
 133 {
 134         if (!thread) {
 135                 return;
 136         }
 137         assert(thread->ref.refcount);
 138         urcu_ref_put(&thread->ref, lttng_thread_release);
 139 }
 140
 141 const char *lttng_thread_get_name(const struct lttng_thread *thread)
 142 {
 143         return thread->name;
 144 }
 145
 146 static
 147 bool _lttng_thread_shutdown(struct lttng_thread *thread)
 148 {
 149         int ret;
 150         void *status;
 151         bool result = true;
 152
 153         DBG("Shutting down \"%s\" thread", thread->name);
 154         if (thread->shutdown) {
 155                 result = thread->shutdown(thread->data);
 156                 if (!result) {
 157                         result = false;
 158                         goto end;
 159                 }
 160         }
 161
 162         ret = pthread_join(thread->thread, &status);
 163         if (ret) {
 164                 PERROR("Failed to join \"%s\" thread", thread->name);
 165                 result = false;
 166                 goto end;
 167         }
 168         DBG("Joined thread \"%s\"", thread->name);
 169 end:
 170         return result;
 171 }
 172
 173 bool lttng_thread_shutdown(struct lttng_thread *thread)
 174 {
 175         const bool result = _lttng_thread_shutdown(thread);
 176
 177         if (result) {
 178                 /* Release the list's reference to the thread. */
 179                 pthread_mutex_lock(&thread_list.lock);
 180                 cds_list_del(&thread->node);
 181                 lttng_thread_put(thread);
 182                 pthread_mutex_unlock(&thread_list.lock);
 183         }
 184         return result;
 185 }
 186
 187 void lttng_thread_list_shutdown_orphans(void)
 188 {
 189         struct lttng_thread *thread, *tmp;
 190
 191         pthread_mutex_lock(&thread_list.lock);
 192         cds_list_for_each_entry_safe(thread, tmp, &thread_list.head, node) {
 193                 bool result;
 194                 const long ref = uatomic_read(&thread->ref.refcount);
 195
 196                 if (ref != 1) {
 197                         /*
 198                          * Other external references to the thread exist, skip.
 199                          */
 200                         continue;
 201                 }
 202
 203                 result = _lttng_thread_shutdown(thread);
 204                 if (!result) {
 205                         ERR("Failed to shutdown thread \"%s\"", thread->name);
 206                 }
 207         }
 208         pthread_mutex_unlock(&thread_list.lock);
 209 }