Normal multi-threaded applications should not need these the
predicates from this section because almost any usage of these
predicates is unsafe. For example checking the existence of a thread
before signalling it is of no use as it may vanish between the two
calls. Catching exceptions using catch/3
is the only safe way to deal with thread-existence errors.
These predicates are provided for diagnosis and monitoring tasks. See
also section 8.5, describing more
high-level primitives.
- thread_property(?Id,
?Property)
-
True if thread Id has Property. Either or both
arguments may be unbound, enumerating all relations on backtracking.
Calling thread_property/2
does not influence any thread. See also
thread_join/2.
For threads that have an alias-name, this name is returned in Id
instead of the numerical thread identifier. Defined properties are:
- alias(Alias)
-
Alias is the alias name of thread Id.
- detached(Boolean)
-
Current detached status of the thread.
- status(Status)
-
Current status of the thread. Status is one of:
- running
-
The thread is running. This is the initial status of a thread. Please
note that threads waiting for something are considered running too.
- false
-
The Goal of the thread has been completed and failed.
- true
-
The Goal of the thread has been completed and succeeded.
- exited(Term)
-
The Goal of the thread has been terminated using thread_exit/1
with Term as argument. If the underlying native thread has
exited (using pthread_exit()) Term is unbound.
- exception(Term)
-
The Goal of the thread has been terminated due to an uncaught
exception (see throw/1
and catch/3).
- thread_statistics(+Id,
+Key, -Value)
-
Obtains statistical information on thread Id as statistics/2
does in single-threaded applications. This call supports all keys of statistics/2,
although only stack sizes and CPU time yield different values for each
thread.75Getting the CPU-time of a
specific thread is not supported on all platforms. On some platforms it
returns total process CPU time instead of the thread CPU time. Thread
CPU time is supported on MS-Windows and most recent Linux versions.
- mutex_statistics
-
Print usage statistics on internal mutexes and mutexes associated with
dynamic predicates. For each mutex two numbers are printed: the number
of times the mutex was acquired and the number of collisions:
the number times the calling thread has to wait for the mutex. The
collision-count is not available on MS-Windows. Generally collision
count is close to zero on single-CPU hardware.
