src/bin/lttng-sessiond/thread.cpp

   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.hpp"
   9 #include <urcu/list.h>
  10 #include <urcu/ref.h>
  11 #include <pthread.h>
  12 #include <common/macros.hpp>
  13 #include <common/error.hpp>
  14 #include <common/defaults.hpp>
  15
  16 namespace {
  17 struct thread_list {
  18         struct cds_list_head head;
  19         pthread_mutex_t lock;
  20 } thread_list = {
  21         .head = CDS_LIST_HEAD_INIT(thread_list.head),
  22         .lock = PTHREAD_MUTEX_INITIALIZER,
  23 };
  24 } /* namespace */
  25
  26 struct lttng_thread {
  27         struct urcu_ref ref;
  28         struct cds_list_head node;
  29         pthread_t thread;
  30         const char *name;
  31         /* Main thread function */
  32         lttng_thread_entry_point entry;
  33         /*
  34          * Thread-specific shutdown method. Allows threads to implement their
  35          * own shutdown mechanism as some of them use a structured message
  36          * passed through a command queue and some rely on a dedicated "quit"
  37          * pipe.
  38          */
  39         lttng_thread_shutdown_cb shutdown;
  40         lttng_thread_cleanup_cb cleanup;
  41         /* Thread implementation-specific data. */
  42         void *data;
  43 };
  44
  45 static
  46 void lttng_thread_destroy(struct lttng_thread *thread)
  47 {
  48         if (thread->cleanup) {
  49                 thread->cleanup(thread->data);
  50         }
  51         free(thread);
  52 }
  53
  54 static
  55 void lttng_thread_release(struct urcu_ref *ref)
  56 {
  57         lttng_thread_destroy(lttng::utils::container_of(ref, &lttng_thread::ref));
  58 }
  59
  60 static
  61 void *launch_thread(void *data)
  62 {
  63         void *ret;
  64         struct lttng_thread *thread = (struct lttng_thread *) data;
  65
  66         logger_set_thread_name(thread->name, true);
  67         DBG("Entering thread entry point");
  68         ret = thread->entry(thread->data);
  69         DBG("Thread entry point has returned");
  70         return ret;
  71 }
  72
  73 struct lttng_thread *lttng_thread_create(const char *name,
  74                 lttng_thread_entry_point entry,
  75                 lttng_thread_shutdown_cb shutdown,
  76                 lttng_thread_cleanup_cb cleanup,
  77                 void *thread_data)
  78 {
  79         int ret;
  80         struct lttng_thread *thread;
  81
  82         thread = zmalloc<lttng_thread>();
  83         if (!thread) {
  84                 goto error_alloc;
  85         }
  86
  87         urcu_ref_init(&thread->ref);
  88         CDS_INIT_LIST_HEAD(&thread->node);
  89         /*
  90          * Thread names are assumed to be statically allocated strings.
  91          * It is unnecessary to copy this attribute.
  92          */
  93         thread->name = name;
  94         thread->entry = entry;
  95         thread->shutdown = shutdown;
  96         thread->cleanup = cleanup;
  97         thread->data = thread_data;
  98
  99         pthread_mutex_lock(&thread_list.lock);
 100         /*
 101          * Add the thread at the head of the list to shutdown threads in the
 102          * opposite order of their creation. A reference is taken for the
 103          * thread list which will be released on shutdown of the thread.
 104          */
 105         cds_list_add(&thread->node, &thread_list.head);
 106         (void) lttng_thread_get(thread);
 107
 108         ret = pthread_create(&thread->thread, default_pthread_attr(),
 109                         launch_thread, thread);
 110         if (ret) {
 111                 PERROR("Failed to create \"%s\" thread", thread->name);
 112                 goto error_pthread_create;
 113         }
 114
 115         pthread_mutex_unlock(&thread_list.lock);
 116         return thread;
 117
 118 error_pthread_create:
 119         cds_list_del(&thread->node);
 120         /* Release list reference. */
 121         lttng_thread_put(thread);
 122         pthread_mutex_unlock(&thread_list.lock);
 123         /* Release initial reference. */
 124         lttng_thread_put(thread);
 125 error_alloc:
 126         return NULL;
 127 }
 128
 129 bool lttng_thread_get(struct lttng_thread *thread)
 130 {
 131         return urcu_ref_get_unless_zero(&thread->ref);
 132 }
 133
 134 void lttng_thread_put(struct lttng_thread *thread)
 135 {
 136         if (!thread) {
 137                 return;
 138         }
 139         LTTNG_ASSERT(thread->ref.refcount);
 140         urcu_ref_put(&thread->ref, lttng_thread_release);
 141 }
 142
 143 const char *lttng_thread_get_name(const struct lttng_thread *thread)
 144 {
 145         return thread->name;
 146 }
 147
 148 static
 149 bool _lttng_thread_shutdown(struct lttng_thread *thread)
 150 {
 151         int ret;
 152         void *status;
 153         bool result = true;
 154
 155         DBG("Shutting down \"%s\" thread", thread->name);
 156         if (thread->shutdown) {
 157                 result = thread->shutdown(thread->data);
 158                 if (!result) {
 159                         result = false;
 160                         goto end;
 161                 }
 162         }
 163
 164         ret = pthread_join(thread->thread, &status);
 165         if (ret) {
 166                 PERROR("Failed to join \"%s\" thread", thread->name);
 167                 result = false;
 168                 goto end;
 169         }
 170         DBG("Joined thread \"%s\"", thread->name);
 171 end:
 172         return result;
 173 }
 174
 175 bool lttng_thread_shutdown(struct lttng_thread *thread)
 176 {
 177         const bool result = _lttng_thread_shutdown(thread);
 178
 179         if (result) {
 180                 /* Release the list's reference to the thread. */
 181                 pthread_mutex_lock(&thread_list.lock);
 182                 cds_list_del(&thread->node);
 183                 lttng_thread_put(thread);
 184                 pthread_mutex_unlock(&thread_list.lock);
 185         }
 186         return result;
 187 }
 188
 189 void lttng_thread_list_shutdown_orphans(void)
 190 {
 191         struct lttng_thread *thread, *tmp;
 192
 193         pthread_mutex_lock(&thread_list.lock);
 194         cds_list_for_each_entry_safe(thread, tmp, &thread_list.head, node) {
 195                 bool result;
 196                 const long ref = uatomic_read(&thread->ref.refcount);
 197
 198                 if (ref != 1) {
 199                         /*
 200                          * Other external references to the thread exist, skip.
 201                          */
 202                         continue;
 203                 }
 204
 205                 result = _lttng_thread_shutdown(thread);
 206                 if (!result) {
 207                         ERR("Failed to shutdown thread \"%s\"", thread->name);
 208                 }
 209         }
 210         pthread_mutex_unlock(&thread_list.lock);
 211 }