Struct tarantool::fiber::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::fiber::Cond;
let cond = Cond::new();
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: Duration) -> bool

Suspend the execution of the current fiber (i.e. yield) until Self::signal or Self::broadcast is called or a timeout is exceeded.

Like pthread_cond, Cond can issue spurious wake ups caused by explicit fiber::wakeup or fiber::cancel calls. Keep this in mind when designing your algorithms.

Returns:

• true if cond was signalled or fiber was awoken by other means.
• false on timeout, last TarantoolError::last is set to TimedOut
• false if current fiber was cancelled (check fiber::is_cancelled).

pub fn wait_deadline(&self, deadline: Instant) -> bool

Suspend the execution of the current fiber (i.e. yield) until Self::signal or Self::broadcast is called or a deadline is reached.

Like pthread_cond, Cond can issue spurious wake ups caused by explicit fiber::wakeup or fiber::cancel calls. Keep this in mind when designing your algorithms.

This will call fiber::clock internally to compute the relative timeout.

Returns:

• true if cond was signalled or fiber was awoken by other means.
• false on deadline, last TarantoolError::last is set to TimedOut
• false if current fiber was cancelled (check fiber::is_cancelled).

pub fn wait(&self) -> bool

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

Like pthread_cond, Cond can issue spurious wake ups caused by explicit fiber::wakeup or fiber::cancel calls. Keep this in mind when designing your algorithms.

Returns:

• true if cond was signalled or fiber was awoken by other means.
• false if current fiber was cancelled (check fiber::is_cancelled).

Trait Implementations

impl Debug for Cond

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Cond

fn default() -> Self

Returns the “default value” for a type.

impl Drop for Cond

fn drop(&mut self)

Executes the destructor for this type.