lib/ovs-thread.c

   1 /*
   2  * Copyright (c) 2013 Nicira, Inc.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at:
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #include <config.h>
  18 #include "ovs-thread.h"
  19 #include <errno.h>
  20 #include <poll.h>
  21 #include <stdlib.h>
  22 #include <unistd.h>
  23 #include "compiler.h"
  24 #include "poll-loop.h"
  25 #include "socket-util.h"
  26 #include "util.h"
  27
  28 #ifdef __CHECKER__
  29 /* Omit the definitions in this file because they are somewhat difficult to
  30  * write without prompting "sparse" complaints, without ugliness or
  31  * cut-and-paste.  Since "sparse" is just a checker, not a compiler, it
  32  * doesn't matter that we don't define them. */
  33 #else
  34 #include "vlog.h"
  35
  36 VLOG_DEFINE_THIS_MODULE(ovs_thread);
  37
  38 /* If there is a reason that we cannot fork anymore (unless the fork will be
  39  * immediately followed by an exec), then this points to a string that
  40  * explains why. */
  41 static const char *must_not_fork;
  42
  43 /* True if we created any threads beyond the main initial thread. */
  44 static bool multithreaded;
  45
  46 #define XPTHREAD_FUNC1(FUNCTION, PARAM1)                \
  47     void                                                \
  48     x##FUNCTION(PARAM1 arg1)                            \
  49     {                                                   \
  50         int error = FUNCTION(arg1);                     \
  51         if (OVS_UNLIKELY(error)) {                      \
  52             ovs_abort(error, "%s failed", #FUNCTION);   \
  53         }                                               \
  54     }
  55 #define XPTHREAD_TRY_FUNC1(FUNCTION, PARAM1)            \
  56     int                                                 \
  57     x##FUNCTION(PARAM1 arg1)                            \
  58     {                                                   \
  59         int error = FUNCTION(arg1);                     \
  60         if (OVS_UNLIKELY(error && error != EBUSY)) {    \
  61             ovs_abort(error, "%s failed", #FUNCTION);   \
  62         }                                               \
  63         return error;                                   \
  64     }
  65 #define XPTHREAD_FUNC2(FUNCTION, PARAM1, PARAM2)        \
  66     void                                                \
  67     x##FUNCTION(PARAM1 arg1, PARAM2 arg2)               \
  68     {                                                   \
  69         int error = FUNCTION(arg1, arg2);               \
  70         if (OVS_UNLIKELY(error)) {                      \
  71             ovs_abort(error, "%s failed", #FUNCTION);   \
  72         }                                               \
  73     }
  74
  75 XPTHREAD_FUNC2(pthread_mutex_init, pthread_mutex_t *, pthread_mutexattr_t *);
  76 XPTHREAD_FUNC1(pthread_mutex_destroy, pthread_mutex_t *);
  77 XPTHREAD_FUNC1(pthread_mutex_lock, pthread_mutex_t *);
  78 XPTHREAD_FUNC1(pthread_mutex_unlock, pthread_mutex_t *);
  79 XPTHREAD_TRY_FUNC1(pthread_mutex_trylock, pthread_mutex_t *);
  80
  81 XPTHREAD_FUNC1(pthread_mutexattr_init, pthread_mutexattr_t *);
  82 XPTHREAD_FUNC1(pthread_mutexattr_destroy, pthread_mutexattr_t *);
  83 XPTHREAD_FUNC2(pthread_mutexattr_settype, pthread_mutexattr_t *, int);
  84 XPTHREAD_FUNC2(pthread_mutexattr_gettype, pthread_mutexattr_t *, int *);
  85
  86 XPTHREAD_FUNC2(pthread_rwlock_init,
  87                pthread_rwlock_t *, pthread_rwlockattr_t *);
  88 XPTHREAD_FUNC1(pthread_rwlock_destroy, pthread_rwlock_t *);
  89 XPTHREAD_FUNC1(pthread_rwlock_rdlock, pthread_rwlock_t *);
  90 XPTHREAD_FUNC1(pthread_rwlock_wrlock, pthread_rwlock_t *);
  91 XPTHREAD_FUNC1(pthread_rwlock_unlock, pthread_rwlock_t *);
  92 XPTHREAD_TRY_FUNC1(pthread_rwlock_tryrdlock, pthread_rwlock_t *);
  93 XPTHREAD_TRY_FUNC1(pthread_rwlock_trywrlock, pthread_rwlock_t *);
  94
  95 XPTHREAD_FUNC2(pthread_cond_init, pthread_cond_t *, pthread_condattr_t *);
  96 XPTHREAD_FUNC1(pthread_cond_destroy, pthread_cond_t *);
  97 XPTHREAD_FUNC1(pthread_cond_signal, pthread_cond_t *);
  98 XPTHREAD_FUNC1(pthread_cond_broadcast, pthread_cond_t *);
  99 XPTHREAD_FUNC2(pthread_cond_wait, pthread_cond_t *, pthread_mutex_t *);
 100
 101 typedef void destructor_func(void *);
 102 XPTHREAD_FUNC2(pthread_key_create, pthread_key_t *, destructor_func *);
 103
 104 void
 105 xpthread_create(pthread_t *threadp, pthread_attr_t *attr,
 106                 void *(*start)(void *), void *arg)
 107 {
 108     pthread_t thread;
 109     int error;
 110
 111     forbid_forking("multiple threads exist");
 112     multithreaded = true;
 113
 114     error = pthread_create(threadp ? threadp : &thread, attr, start, arg);
 115     if (error) {
 116         ovs_abort(error, "pthread_create failed");
 117     }
 118 }
 119 \f
 120 bool
 121 ovsthread_once_start__(struct ovsthread_once *once)
 122 {
 123     xpthread_mutex_lock(&once->mutex);
 124     if (!ovsthread_once_is_done__(once)) {
 125         return false;
 126     }
 127     xpthread_mutex_unlock(&once->mutex);
 128     return true;
 129 }
 130
 131 void OVS_RELEASES(once)
 132 ovsthread_once_done(struct ovsthread_once *once)
 133 {
 134     atomic_store(&once->done, true);
 135     xpthread_mutex_unlock(&once->mutex);
 136 }
 137 \f
 138 /* Asserts that the process has not yet created any threads (beyond the initial
 139  * thread).  */
 140 void
 141 (assert_single_threaded)(const char *where)
 142 {
 143     if (multithreaded) {
 144         VLOG_FATAL("%s: attempted operation not allowed when multithreaded",
 145                    where);
 146     }
 147 }
 148
 149 /* Forks the current process (checking that this is allowed).  Aborts with
 150  * VLOG_FATAL if fork() returns an error, and otherwise returns the value
 151  * returned by fork().  */
 152 pid_t
 153 (xfork)(const char *where)
 154 {
 155     pid_t pid;
 156
 157     if (must_not_fork) {
 158         VLOG_FATAL("%s: attempted to fork but forking not allowed (%s)",
 159                    where, must_not_fork);
 160     }
 161
 162     pid = fork();
 163     if (pid < 0) {
 164         VLOG_FATAL("fork failed (%s)", ovs_strerror(errno));
 165     }
 166     return pid;
 167 }
 168
 169 /* Notes that the process must not call fork() from now on, for the specified
 170  * 'reason'.  (The process may still fork() if it execs itself immediately
 171  * afterward.) */
 172 void
 173 forbid_forking(const char *reason)
 174 {
 175     ovs_assert(reason != NULL);
 176     must_not_fork = reason;
 177 }
 178
 179 /* Returns true if the process is allowed to fork, false otherwise. */
 180 bool
 181 may_fork(void)
 182 {
 183     return !must_not_fork;
 184 }
 185 #endif