The type of mutexes.

Return a new mutex.

Unlock the given mutex. Other tasks suspended trying to lock the mutex will restart. The mutex must have been previously locked by the thread that calls unlock.

• raises Sys_error

  was not raised when unlocking an unlocked mutex or when unlocking a mutex from a different task.

Lock the given mutex. Only one task can have the mutex locked at a time. A task that attempts to lock a mutex already locked by another thread will suspend until the other thread unlocks the mutex.

Same as lock, but does not suspend the calling thread if the mutex is already locked: just return false immediately in that case. If the mutex is unlocked, lock it and return true.

protect t fn runs fn in a critical section where t is locked (atomically); it then takes care of releasing t whether fn returned a value or raised an exception.

The unlocking operation is guaranteed to always takes place, even in the event a cancellation is ordered by the parent task.