Struct Cond

pub struct Cond { /* private fields */ }

Conditional variable for cooperative multitasking (fibers).

A cond (short for “condition variable”) is a synchronization primitive that allow fibers to yield until some predicate is satisfied. Fiber conditions have two basic operations - wait() and signal(). cond.wait() suspends execution of fiber (i.e. yields) until cond.signal() is called.

Example:

use tarantool_module::fiber::Cond;
let cond = fiber.cond();
cond.wait();

The job will hang because cond.wait() – will go to sleep until the condition variable changes.

// Call from another fiber:
cond.signal();

The waiting stopped, and the cond.wait() function returned true.

This example depended on the use of a global conditional variable with the arbitrary name cond. In real life, programmers would make sure to use different conditional variable names for different applications.

Unlike pthread_cond, Cond doesn’t require mutex/latch wrapping.

Implementations

impl Cond

• call Cond::new() to create a named condition variable, which will be called cond for examples in this section.
• call cond.wait() to make a fiber wait for a signal via a condition variable.
• call cond.signal() to send a signal to wake up a single fiber that has executed cond.wait().
• call cond.broadcast() to send a signal to all fibers that have executed cond.wait().

pub fn new() -> Self

Instantiate a new fiber cond object.

pub fn signal(&self)

Wake one fiber waiting for the cond. Does nothing if no one is waiting. Does not yield.

pub fn broadcast(&self)

Wake up all fibers waiting for the cond. Does not yield.

pub fn wait_timeout(&self, timeout: f64) -> bool

Suspend the execution of the current fiber (i.e. yield) until signal() is called.

Like pthread_cond, FiberCond can issue spurious wake ups caused by explicit Fiber::wakeup() or Fiber::cancel() calls. It is highly recommended to wrap calls to this function into a loop and check an actual predicate and fiber_testcancel() on every iteration.

• timeout - timeout in seconds

Returns:

• true on signal() call or a spurious wake up.
• false on timeout, diag is set to TimedOut

pub fn wait(&self) -> bool

Shortcut for wait_timeout().

Trait Implementations

impl Drop for Cond

fn drop(&mut self)

Executes the destructor for this type.