lock-and-condition-variable-signal

lock-and-condition-variable-signal Function

Summary

Locks, applies a setup function, calls condition-variable-signal and unlocks.

Package

Signature

lock-and-condition-variable-signal lock condvar lock-timeout setup-function &rest args => signaledp

Arguments

`lock`⇩	A lock.
`condvar`⇩	A condition-variable.
`lock-timeout`⇩	A non-negative real or `nil`.
`setup-function`⇩	A function designator.
`args`⇩	Arguments to `setup-function`.

Values

signaledp

A generalized boolean.

Description

The function lock-and-condition-variable-signal locks the lock lock, applies setup-function to args, calls condition-variable-signal with condvar and unlocks lock. lock-and-condition-variable-signal makes it easier to avoid mistakes when using a condition-variable.

If lock-timeout is non-nil, then lock-and-condition-variable-signal returns nil if lock cannot be locked within lock-timeout seconds.

lock-and-condition-variable-signal performs the equivalent of:

(mp:with-lock (lock nil lock-timeout)
  (apply setup-function args)
  (mp:condition-variable-signal condvar))

It returns the result of the call to condition-variable-signal.

See condition-variable-signal and with-lock for more details.

Notes

setup-function is called with lock held, so it should do the minimum amount of work and avoid locking other locks. Normally setup-function should only set the cell that the process(es) that wait(s) on the condition-variable condvar check with the predicate in lock-and-condition-variable-wait.