SBCL supports a fairly low-level threading interface that maps onto
the host operating system's concept of threads or lightweight
processes. This means that threads may take advantage of hardware
-multiprocessing on machines that have more than one CPU, but it does
+multiprocessing on machines that have more than one CPU, but it does
not allow Lisp control of the scheduler. This is found in the
SB-THREAD package.
-This requires Linux (2.6+ or systems with NPTL backports) running on the
-x86 or x86-64 architecture, or SunOS (Solaris) on the x86. Support for
-threading on Darwin (Mac OS X) and FreeBSD on the x86 is experimental.
+Threads are part of the default build on x86[-64] Linux only.
+
+They are also experimentally supported on: x86[-64] Darwin (Mac OS X),
+x86[-64] FreeBSD, x86 SunOS (Solaris), and PPC Linux. On these platforms
+threads must be explicitly enabled at build-time, see @file{INSTALL} for
+directions.
@menu
* Threading basics::
* Special Variables::
+* Atomic Operations::
* Mutex Support::
+* Semaphores::
* Waitqueue/condition variables::
+* Barriers::
* Sessions/Debugging::
-* Implementation (Linux x86)::
+* Foreign threads::
+* Implementation (Linux x86/x86-64)::
@end menu
@node Threading basics
(make-thread (lambda () (write-line "Hello, world")))
@end lisp
+@subsection Thread Objects
+
@include struct-sb-thread-thread.texinfo
@include var-sb-thread-star-current-thread-star.texinfo
-@include fun-sb-thread-make-thread.texinfo
-@include fun-sb-thread-thread-alive-p.texinfo
@include fun-sb-thread-list-all-threads.texinfo
-@include condition-sb-thread-interrupt-thread-error.texinfo
-@include fun-sb-thread-interrupt-thread-error-thread.texinfo
+@include fun-sb-thread-thread-alive-p.texinfo
+@include fun-sb-thread-thread-name.texinfo
+
+@subsection Making, Joining, and Yielding Threads
+
+@include fun-sb-thread-make-thread.texinfo
+@include fun-sb-thread-thread-yield.texinfo
+@include fun-sb-thread-join-thread.texinfo
+
+@subsection Asynchronous Operations
+
@include fun-sb-thread-interrupt-thread.texinfo
@include fun-sb-thread-terminate-thread.texinfo
+@subsection Miscellaneous Operations
+
+@include fun-sb-thread-symbol-value-in-thread.texinfo
+
+@subsection Error Conditions
+
+@include condition-sb-thread-thread-error.texinfo
+@include fun-sb-thread-thread-error-thread.texinfo
+
+@c @include condition-sb-thread-symbol-value-in-thread-error.texinfo
+@include condition-sb-thread-interrupt-thread-error.texinfo
+@include condition-sb-thread-join-thread-error.texinfo
+
@node Special Variables
@comment node-name, next, previous, up
@section Special Variables
prints @code{0} and not @code{1} as of 0.9.6.
+@node Atomic Operations
+@comment node-name, next, previous, up
+@section Atomic Operations
+
+SBCL provides a few special purpose atomic operations, particularly
+useful for implementing lockless algorithms.
+
+@include macro-sb-ext-atomic-decf.texinfo
+@include macro-sb-ext-atomic-incf.texinfo
+@include macro-sb-ext-compare-and-swap.texinfo
+
@node Mutex Support
@comment node-name, next, previous, up
@section Mutex Support
@include macro-sb-thread-with-mutex.texinfo
@include macro-sb-thread-with-recursive-lock.texinfo
+@node Semaphores
+@comment node-name, next, previous, up
+@section Semaphores
+
+described here should be considered
+experimental, subject to API changes without notice.
+
+@include struct-sb-thread-semaphore.texinfo
+@include fun-sb-thread-make-semaphore.texinfo
+@include fun-sb-thread-semaphore-count.texinfo
+@include fun-sb-thread-semaphore-name.texinfo
+@include fun-sb-thread-signal-semaphore.texinfo
+@include fun-sb-thread-try-semaphore.texinfo
+@include fun-sb-thread-wait-on-semaphore.texinfo
+
@node Waitqueue/condition variables
@comment node-name, next, previous, up
@section Waitqueue/condition variables
There are three components:
@itemize
-@item
+@item
the condition itself (not represented in code)
-@item
+@item
the condition variable (a.k.a waitqueue) which proxies for it
-@item
-a lock to hold while testing the condition
+@item
+a lock to hold while testing the condition
@end itemize
Important stuff to be aware of:
@itemize
-@item
+@item
when calling condition-wait, you must hold the mutex. condition-wait
will drop the mutex while it waits, and obtain it again before
returning for whatever reason;
-@item
+@item
likewise, you must be holding the mutex around calls to
condition-notify;
-@item
+@item
a process may return from condition-wait in several circumstances: it
is not guaranteed that the underlying condition has become true. You
must check that the resource is ready for whatever you want to do to
(unless *buffer* (return))
(let ((head (car *buffer*)))
(setf *buffer* (cdr *buffer*))
- (format t "reader ~A woke, read ~A~%"
+ (format t "reader ~A woke, read ~A~%"
*current-thread* head))))))
(defun writer ()
(sleep (random 5))
(with-mutex (*buffer-lock*)
(let ((el (intern
- (string (code-char
+ (string (code-char
(+ (char-code #\A) (random 26)))))))
(setf *buffer* (cons el *buffer*)))
(condition-notify *buffer-queue*))))
(make-thread #'writer)
(make-thread #'reader)
-(make-thread #'reader)
+(make-thread #'reader)
@end lisp
@include struct-sb-thread-waitqueue.texinfo
@include fun-sb-thread-condition-notify.texinfo
@include fun-sb-thread-condition-broadcast.texinfo
+@node Barriers
+@comment node-name, next, previous, up
+@section Barriers
+
+These are based on the Linux kernel barrier design, which is in turn
+based on the Alpha CPU memory model. They are presently implemented for
+x86, x86-64, and PPC systems, and behave as compiler barriers on all
+other CPUs.
+
+In addition to explicit use of the @code{sb-thread:barrier} macro, the
+following functions and macros also serve as @code{:memory} barriers:
+
+@itemize
+@item
+@code{sb-ext:atomic-decf} and @code{sb-ext:atomic-incf}.
+@item
+@code{sb-ext:compare-and-swap}.
+@item
+@code{sb-thread:get-mutex}, @code{sb-thread:release-mutex},
+@code{sb-thread:with-mutex} and @code{sb-thread:with-recursive-lock}.
+@item
+@code{sb-thread:signal-semaphore}, @code{sb-thread:try-semaphore} and
+@code{sb-thread:wait-on-semaphore}.
+@item
+@code{sb-thread:condition-wait}, @code{sb-thread:condition-notify} and
+@code{sb-thread:condition-broadcast}.
+@end itemize
+
+@include macro-sb-thread-barrier.texinfo
+
@node Sessions/Debugging
@comment node-name, next, previous, up
@section Sessions/Debugging
A thread which wishes to create a new session can use
@code{sb-thread:with-new-session} to remove itself from the current
session (which it shares with its parent and siblings) and create a
-fresh one.
+fresh one.
# See also @code{sb-thread:make-listener-thread}.
Within a single session, threads arbitrate between themselves for the
@code{sb-ext:quit} terminates all threads in the current session, but
leaves other sessions running.
-@node Implementation (Linux x86)
+@node Foreign threads
+@comment node-name, next, previous, up
+@section Foreign threads
+
+Direct calls to @code{pthread_create} (instead of @code{MAKE-THREAD})
+create threads that SBCL is not aware of, these are called foreign
+threads. Currently, it is not possible to run Lisp code in such
+threads. This means that the Lisp side signal handlers cannot work.
+The best solution is to start foreign threads with signals blocked,
+but since third party libraries may create threads, it is not always
+feasible to do so. As a workaround, upon receiving a signal in a
+foreign thread, SBCL changes the thread's sigmask to block all signals
+that it wants to handle and resends the signal to the current process
+which should land in a thread that does not block it, that is, a Lisp
+thread.
+
+The resignalling trick cannot work for synchronously triggered signals
+(SIGSEGV and co), take care not to trigger any. Resignalling for
+synchronously triggered signals in foreign threads is subject to
+@code{--lose-on-corruption}, see @ref{Runtime Options}.
+
+@node Implementation (Linux x86/x86-64)
@comment node-name, next, previous, up
@section Implementation (Linux x86/x86-64)
projects / sbcl.git / blobdiff