class Mutex
Mutex implements a simple semaphore that can be used to coordinate access to shared data from multiple concurrent threads.
Example:
require 'thread' semaphore = Mutex.new a = Thread.new { semaphore.synchronize { # access shared resource } } b = Thread.new { semaphore.synchronize { # access shared resource } }
In Files
- thread.c
Parent
Public Class Methods
Creates a new Mutex
static VALUE
mutex_initialize(VALUE self)
{
return self;
}
Public Instance Methods
Attempts to grab the lock and waits if it isn't available. Raises
ThreadError if mutex was locked by the current
thread.
VALUE
rb_mutex_lock(VALUE self)
{
rb_thread_t *th = GET_THREAD();
rb_mutex_t *mutex;
GetMutexPtr(self, mutex);
/* When running trap handler */
if (!mutex->allow_trap && th->interrupt_mask & TRAP_INTERRUPT_MASK) {
rb_raise(rb_eThreadError, "can't be called from trap context");
}
if (rb_mutex_trylock(self) == Qfalse) {
if (mutex->th == GET_THREAD()) {
rb_raise(rb_eThreadError, "deadlock; recursive locking");
}
while (mutex->th != th) {
int interrupted;
enum rb_thread_status prev_status = th->status;
volatile int timeout_ms = 0;
struct rb_unblock_callback oldubf;
set_unblock_function(th, lock_interrupt, mutex, &oldubf, FALSE);
th->status = THREAD_STOPPED_FOREVER;
th->locking_mutex = self;
native_mutex_lock(&mutex->lock);
th->vm->sleeper++;
/*
* Carefully! while some contended threads are in lock_func(),
* vm->sleepr is unstable value. we have to avoid both deadlock
* and busy loop.
*/
if ((vm_living_thread_num(th->vm) == th->vm->sleeper) &&
!patrol_thread) {
timeout_ms = 100;
patrol_thread = th;
}
GVL_UNLOCK_BEGIN();
interrupted = lock_func(th, mutex, (int)timeout_ms);
native_mutex_unlock(&mutex->lock);
GVL_UNLOCK_END();
if (patrol_thread == th)
patrol_thread = NULL;
reset_unblock_function(th, &oldubf);
th->locking_mutex = Qfalse;
if (mutex->th && interrupted == 2) {
rb_check_deadlock(th->vm);
}
if (th->status == THREAD_STOPPED_FOREVER) {
th->status = prev_status;
}
th->vm->sleeper--;
if (mutex->th == th) mutex_locked(th, self);
if (interrupted) {
RUBY_VM_CHECK_INTS_BLOCKING(th);
}
}
}
return self;
}
Returns true if this lock is currently held by some thread.
VALUE
rb_mutex_locked_p(VALUE self)
{
rb_mutex_t *mutex;
GetMutexPtr(self, mutex);
return mutex->th ? Qtrue : Qfalse;
}
Returns true if this lock is currently held by current thread.
This API is experimental, and subject to change.
VALUE
rb_mutex_owned_p(VALUE self)
{
VALUE owned = Qfalse;
rb_thread_t *th = GET_THREAD();
rb_mutex_t *mutex;
GetMutexPtr(self, mutex);
if (mutex->th == th)
owned = Qtrue;
return owned;
}
Releases the lock and sleeps timeout seconds if it is given
and non-nil or forever. Raises ThreadError if
mutex wasn't locked by the current thread.
When the thread is next woken up, it will attempt to reacquire the lock.
Note that this method can wakeup without explicit Thread#wakeup call. For example, receiving signal and so on.
static VALUE
mutex_sleep(int argc, VALUE *argv, VALUE self)
{
VALUE timeout;
rb_scan_args(argc, argv, "01", &timeout);
return rb_mutex_sleep(self, timeout);
}
Obtains a lock, runs the block, and releases the lock when the block
completes. See the example under Mutex.
static VALUE
rb_mutex_synchronize_m(VALUE self, VALUE args)
{
if (!rb_block_given_p()) {
rb_raise(rb_eThreadError, "must be called with a block");
}
return rb_mutex_synchronize(self, rb_yield, Qundef);
}
Attempts to obtain the lock and returns immediately. Returns
true if the lock was granted.
VALUE
rb_mutex_trylock(VALUE self)
{
rb_mutex_t *mutex;
VALUE locked = Qfalse;
GetMutexPtr(self, mutex);
native_mutex_lock(&mutex->lock);
if (mutex->th == 0) {
mutex->th = GET_THREAD();
locked = Qtrue;
mutex_locked(GET_THREAD(), self);
}
native_mutex_unlock(&mutex->lock);
return locked;
}
Releases the lock. Raises ThreadError if mutex
wasn't locked by the current thread.
VALUE
rb_mutex_unlock(VALUE self)
{
const char *err;
rb_mutex_t *mutex;
GetMutexPtr(self, mutex);
err = rb_mutex_unlock_th(mutex, GET_THREAD());
if (err) rb_raise(rb_eThreadError, "%s", err);
return self;
}