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ovs-thread.c
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ovs-thread.c
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/*
* Copyright (c) 2013 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <config.h>
#include "ovs-thread.h"
#include <errno.h>
#include <poll.h>
#include <stdlib.h>
#include <unistd.h>
#include "compiler.h"
#include "hash.h"
#include "poll-loop.h"
#include "socket-util.h"
#include "util.h"
#ifdef __CHECKER__
/* Omit the definitions in this file because they are somewhat difficult to
* write without prompting "sparse" complaints, without ugliness or
* cut-and-paste. Since "sparse" is just a checker, not a compiler, it
* doesn't matter that we don't define them. */
#else
#include "vlog.h"
VLOG_DEFINE_THIS_MODULE(ovs_thread);
/* If there is a reason that we cannot fork anymore (unless the fork will be
* immediately followed by an exec), then this points to a string that
* explains why. */
static const char *must_not_fork;
/* True if we created any threads beyond the main initial thread. */
static bool multithreaded;
#define LOCK_FUNCTION(TYPE, FUN) \
void \
ovs_##TYPE##_##FUN##_at(const struct ovs_##TYPE *l_, \
const char *where) \
OVS_NO_THREAD_SAFETY_ANALYSIS \
{ \
struct ovs_##TYPE *l = CONST_CAST(struct ovs_##TYPE *, l_); \
int error = pthread_##TYPE##_##FUN(&l->lock); \
if (OVS_UNLIKELY(error)) { \
ovs_abort(error, "pthread_%s_%s failed", #TYPE, #FUN); \
} \
l->where = where; \
}
LOCK_FUNCTION(mutex, lock);
LOCK_FUNCTION(rwlock, rdlock);
LOCK_FUNCTION(rwlock, wrlock);
#define TRY_LOCK_FUNCTION(TYPE, FUN) \
int \
ovs_##TYPE##_##FUN##_at(const struct ovs_##TYPE *l_, \
const char *where) \
OVS_NO_THREAD_SAFETY_ANALYSIS \
{ \
struct ovs_##TYPE *l = CONST_CAST(struct ovs_##TYPE *, l_); \
int error = pthread_##TYPE##_##FUN(&l->lock); \
if (OVS_UNLIKELY(error) && error != EBUSY) { \
ovs_abort(error, "pthread_%s_%s failed", #TYPE, #FUN); \
} \
if (!error) { \
l->where = where; \
} \
return error; \
}
TRY_LOCK_FUNCTION(mutex, trylock);
TRY_LOCK_FUNCTION(rwlock, tryrdlock);
TRY_LOCK_FUNCTION(rwlock, trywrlock);
#define UNLOCK_FUNCTION(TYPE, FUN) \
void \
ovs_##TYPE##_##FUN(const struct ovs_##TYPE *l_) \
OVS_NO_THREAD_SAFETY_ANALYSIS \
{ \
struct ovs_##TYPE *l = CONST_CAST(struct ovs_##TYPE *, l_); \
int error; \
l->where = NULL; \
error = pthread_##TYPE##_##FUN(&l->lock); \
if (OVS_UNLIKELY(error)) { \
ovs_abort(error, "pthread_%s_%sfailed", #TYPE, #FUN); \
} \
}
UNLOCK_FUNCTION(mutex, unlock);
UNLOCK_FUNCTION(mutex, destroy);
UNLOCK_FUNCTION(rwlock, unlock);
UNLOCK_FUNCTION(rwlock, destroy);
#define XPTHREAD_FUNC1(FUNCTION, PARAM1) \
void \
x##FUNCTION(PARAM1 arg1) \
{ \
int error = FUNCTION(arg1); \
if (OVS_UNLIKELY(error)) { \
ovs_abort(error, "%s failed", #FUNCTION); \
} \
}
#define XPTHREAD_FUNC2(FUNCTION, PARAM1, PARAM2) \
void \
x##FUNCTION(PARAM1 arg1, PARAM2 arg2) \
{ \
int error = FUNCTION(arg1, arg2); \
if (OVS_UNLIKELY(error)) { \
ovs_abort(error, "%s failed", #FUNCTION); \
} \
}
XPTHREAD_FUNC1(pthread_mutex_lock, pthread_mutex_t *);
XPTHREAD_FUNC1(pthread_mutex_unlock, pthread_mutex_t *);
XPTHREAD_FUNC1(pthread_mutexattr_init, pthread_mutexattr_t *);
XPTHREAD_FUNC1(pthread_mutexattr_destroy, pthread_mutexattr_t *);
XPTHREAD_FUNC2(pthread_mutexattr_settype, pthread_mutexattr_t *, int);
XPTHREAD_FUNC2(pthread_mutexattr_gettype, pthread_mutexattr_t *, int *);
XPTHREAD_FUNC2(pthread_cond_init, pthread_cond_t *, pthread_condattr_t *);
XPTHREAD_FUNC1(pthread_cond_destroy, pthread_cond_t *);
XPTHREAD_FUNC1(pthread_cond_signal, pthread_cond_t *);
XPTHREAD_FUNC1(pthread_cond_broadcast, pthread_cond_t *);
XPTHREAD_FUNC2(pthread_join, pthread_t, void **);
typedef void destructor_func(void *);
XPTHREAD_FUNC2(pthread_key_create, pthread_key_t *, destructor_func *);
XPTHREAD_FUNC2(pthread_setspecific, pthread_key_t, const void *);
static void
ovs_mutex_init__(const struct ovs_mutex *l_, int type)
{
struct ovs_mutex *l = CONST_CAST(struct ovs_mutex *, l_);
pthread_mutexattr_t attr;
int error;
l->where = NULL;
xpthread_mutexattr_init(&attr);
xpthread_mutexattr_settype(&attr, type);
error = pthread_mutex_init(&l->lock, &attr);
if (OVS_UNLIKELY(error)) {
ovs_abort(error, "pthread_mutex_init failed");
}
xpthread_mutexattr_destroy(&attr);
}
/* Initializes 'mutex' as a normal (non-recursive) mutex. */
void
ovs_mutex_init(const struct ovs_mutex *mutex)
{
ovs_mutex_init__(mutex, PTHREAD_MUTEX_ERRORCHECK);
}
/* Initializes 'mutex' as a recursive mutex. */
void
ovs_mutex_init_recursive(const struct ovs_mutex *mutex)
{
ovs_mutex_init__(mutex, PTHREAD_MUTEX_RECURSIVE);
}
void
ovs_rwlock_init(const struct ovs_rwlock *l_)
{
struct ovs_rwlock *l = CONST_CAST(struct ovs_rwlock *, l_);
int error;
l->where = NULL;
error = pthread_rwlock_init(&l->lock, NULL);
if (OVS_UNLIKELY(error)) {
ovs_abort(error, "pthread_rwlock_init failed");
}
}
void
ovs_mutex_cond_wait(pthread_cond_t *cond, const struct ovs_mutex *mutex_)
{
struct ovs_mutex *mutex = CONST_CAST(struct ovs_mutex *, mutex_);
int error = pthread_cond_wait(cond, &mutex->lock);
if (OVS_UNLIKELY(error)) {
ovs_abort(error, "pthread_cond_wait failed");
}
}
DEFINE_EXTERN_PER_THREAD_DATA(ovsthread_id, 0);
struct ovsthread_aux {
void *(*start)(void *);
void *arg;
};
static void *
ovsthread_wrapper(void *aux_)
{
static atomic_uint next_id = ATOMIC_VAR_INIT(1);
struct ovsthread_aux *auxp = aux_;
struct ovsthread_aux aux;
unsigned int id;
atomic_add(&next_id, 1, &id);
*ovsthread_id_get() = id;
aux = *auxp;
free(auxp);
return aux.start(aux.arg);
}
void
xpthread_create(pthread_t *threadp, pthread_attr_t *attr,
void *(*start)(void *), void *arg)
{
struct ovsthread_aux *aux;
pthread_t thread;
int error;
forbid_forking("multiple threads exist");
multithreaded = true;
aux = xmalloc(sizeof *aux);
aux->start = start;
aux->arg = arg;
error = pthread_create(threadp ? threadp : &thread, attr,
ovsthread_wrapper, aux);
if (error) {
ovs_abort(error, "pthread_create failed");
}
}
bool
ovsthread_once_start__(struct ovsthread_once *once)
{
ovs_mutex_lock(&once->mutex);
if (!ovsthread_once_is_done__(once)) {
return false;
}
ovs_mutex_unlock(&once->mutex);
return true;
}
void
ovsthread_once_done(struct ovsthread_once *once)
{
atomic_store(&once->done, true);
ovs_mutex_unlock(&once->mutex);
}
/* Asserts that the process has not yet created any threads (beyond the initial
* thread).
*
* ('where' is used in logging. Commonly one would use
* assert_single_threaded() to automatically provide the caller's source file
* and line number for 'where'.) */
void
assert_single_threaded_at(const char *where)
{
if (multithreaded) {
VLOG_FATAL("%s: attempted operation not allowed when multithreaded",
where);
}
}
/* Forks the current process (checking that this is allowed). Aborts with
* VLOG_FATAL if fork() returns an error, and otherwise returns the value
* returned by fork().
*
* ('where' is used in logging. Commonly one would use xfork() to
* automatically provide the caller's source file and line number for
* 'where'.) */
pid_t
xfork_at(const char *where)
{
pid_t pid;
if (must_not_fork) {
VLOG_FATAL("%s: attempted to fork but forking not allowed (%s)",
where, must_not_fork);
}
pid = fork();
if (pid < 0) {
VLOG_FATAL("%s: fork failed (%s)", where, ovs_strerror(errno));
}
return pid;
}
/* Notes that the process must not call fork() from now on, for the specified
* 'reason'. (The process may still fork() if it execs itself immediately
* afterward.) */
void
forbid_forking(const char *reason)
{
ovs_assert(reason != NULL);
must_not_fork = reason;
}
/* Returns true if the process is allowed to fork, false otherwise. */
bool
may_fork(void)
{
return !must_not_fork;
}
/* ovsthread_counter.
*
* We implement the counter as an array of N_COUNTERS individual counters, each
* with its own lock. Each thread uses one of the counters chosen based on a
* hash of the thread's ID, the idea being that, statistically, different
* threads will tend to use different counters and therefore avoid
* interfering with each other.
*
* Undoubtedly, better implementations are possible. */
/* Basic counter structure. */
struct ovsthread_counter__ {
struct ovs_mutex mutex;
unsigned long long int value;
};
/* Pad the basic counter structure to 64 bytes to avoid cache line
* interference. */
struct ovsthread_counter {
struct ovsthread_counter__ c;
char pad[ROUND_UP(sizeof(struct ovsthread_counter__), 64)
- sizeof(struct ovsthread_counter__)];
};
#define N_COUNTERS 16
struct ovsthread_counter *
ovsthread_counter_create(void)
{
struct ovsthread_counter *c;
int i;
c = xmalloc(N_COUNTERS * sizeof *c);
for (i = 0; i < N_COUNTERS; i++) {
ovs_mutex_init(&c[i].c.mutex);
c[i].c.value = 0;
}
return c;
}
void
ovsthread_counter_destroy(struct ovsthread_counter *c)
{
if (c) {
int i;
for (i = 0; i < N_COUNTERS; i++) {
ovs_mutex_destroy(&c[i].c.mutex);
}
free(c);
}
}
void
ovsthread_counter_inc(struct ovsthread_counter *c, unsigned long long int n)
{
c = &c[hash_int(ovsthread_id_self(), 0) % N_COUNTERS];
ovs_mutex_lock(&c->c.mutex);
c->c.value += n;
ovs_mutex_unlock(&c->c.mutex);
}
unsigned long long int
ovsthread_counter_read(const struct ovsthread_counter *c)
{
unsigned long long int sum;
int i;
sum = 0;
for (i = 0; i < N_COUNTERS; i++) {
ovs_mutex_lock(&c[i].c.mutex);
sum += c[i].c.value;
ovs_mutex_unlock(&c[i].c.mutex);
}
return sum;
}
/* Parses /proc/cpuinfo for the total number of physical cores on this system
* across all CPU packages, not counting hyper-threads.
*
* Sets *n_cores to the total number of cores on this system, or 0 if the
* number cannot be determined. */
static void
parse_cpuinfo(long int *n_cores)
{
static const char file_name[] = "/proc/cpuinfo";
char line[128];
uint64_t cpu = 0; /* Support up to 64 CPU packages on a single system. */
long int cores = 0;
FILE *stream;
stream = fopen(file_name, "r");
if (!stream) {
VLOG_DBG("%s: open failed (%s)", file_name, ovs_strerror(errno));
return;
}
while (fgets(line, sizeof line, stream)) {
unsigned int id;
/* Find the next CPU package. */
if (ovs_scan(line, "physical id%*[^:]: %u", &id)) {
if (id > 63) {
VLOG_WARN("Counted over 64 CPU packages on this system. "
"Parsing %s for core count may be inaccurate.",
file_name);
cores = 0;
break;
}
if (cpu & (1 << id)) {
/* We've already counted this package's cores. */
continue;
}
cpu |= 1 << id;
/* Find the number of cores for this package. */
while (fgets(line, sizeof line, stream)) {
int count;
if (ovs_scan(line, "cpu cores%*[^:]: %u", &count)) {
cores += count;
break;
}
}
}
}
fclose(stream);
*n_cores = cores;
}
/* Returns the total number of cores on this system, or 0 if the number cannot
* be determined.
*
* Tries not to count hyper-threads, but may be inaccurate - particularly on
* platforms that do not provide /proc/cpuinfo, but also if /proc/cpuinfo is
* formatted different to the layout that parse_cpuinfo() expects. */
int
count_cpu_cores(void)
{
static struct ovsthread_once once = OVSTHREAD_ONCE_INITIALIZER;
static long int n_cores;
if (ovsthread_once_start(&once)) {
parse_cpuinfo(&n_cores);
if (!n_cores) {
n_cores = sysconf(_SC_NPROCESSORS_ONLN);
}
ovsthread_once_done(&once);
}
return n_cores > 0 ? n_cores : 0;
}
#endif