mutex_lock(m, @optional timeout = false, t = self())

Lock the mutex m. Return a boolean value.

If m is currently locked, the current task waits until m is unlocked, or until timeout is reached (if timeout is supplied). If timeout is reached, mutex_lock returns false. Otherwise, the state of m is changed as follows:

if t is false, m becomes locked/not-owned, otherwise, if t is a task and it is terminated m becomes unlocked/abandoned, otherwise m becomes locked/owned with t as the owner.

After changing the state of m, an abandoned-mutex-exception object is raised if m was unlocked/abandoned before the state change, otherwise mutex_lock returns true. It is not an error if m is owned by the current task (but the current task will have to wait).

If provided, timeout should be an exact or inexact real number representing a relative time in seconds from the moment mutex_lock was called.


// updating shared state without a data race:          
let x = 0
let mx = mutex()

function incx()
{ mutex_lock(mx)
  x = inc(x)
  mutex_unlock(mx) }

// 2          

Also see:


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