X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=doc%2Fmanual%2Fthreading.texinfo;h=6219f67897e2c936e86f27a7e48256b0fffe6222;hb=bd08bc2c6bc19c195f84b3facf7ab949a37bd5d6;hp=944892a2c490394981ef7fcaab7651f9330caefb;hpb=94ea2b2082deaa0331dfb66fa6af6ca12dd8dc83;p=sbcl.git diff --git a/doc/manual/threading.texinfo b/doc/manual/threading.texinfo index 944892a..6219f67 100644 --- a/doc/manual/threading.texinfo +++ b/doc/manual/threading.texinfo @@ -5,38 +5,73 @@ 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 x86 and Linux kernel 2.6 or systems with NPTL backports. +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. @menu -* Special Variables:: -* Mutex Support:: -* Waitqueue/condition variables:: -* Sessions/Debugging:: -* Implementation (Linux x86):: +* Threading basics:: +* Special Variables:: +* Mutex Support:: +* Semaphores:: +* Waitqueue/condition variables:: +* Sessions/Debugging:: +* Implementation (Linux x86):: @end menu +@node Threading basics +@comment node-name, next, previous, up +@section Threading basics + +@lisp +(make-thread (lambda () (write-line "Hello, world"))) +@end lisp + +@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-join-thread.texinfo +@include condition-sb-thread-join-thread-error.texinfo +@include fun-sb-thread-join-thread-error-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-interrupt-thread.texinfo +@include fun-sb-thread-terminate-thread.texinfo +@include fun-sb-thread-thread-yield.texinfo + @node Special Variables @comment node-name, next, previous, up @section Special Variables The interaction of special variables with multiple threads is mostly -as one would expect, but users of other Lisps are warned that the -behaviour of locally bound specials differs in places from what they -may expect. +as one would expect, with behaviour very similar to other +implementations. @itemize -@item +@item global special values are visible across all threads; @item bindings (e.g. using LET) are local to the thread; @item -initial values in a new thread are taken from the thread that created it. +threads do not inherit dynamic bindings from the parent thread @end itemize +The last point means that + +@lisp +(defparameter *x* 0) +(let ((*x* 1)) + (sb-thread:make-thread (lambda () (print *x*)))) +@end lisp + +prints @code{0} and not @code{1} as of 0.9.6. + @node Mutex Support @comment node-name, next, previous, up @section Mutex Support @@ -62,13 +97,35 @@ if you want a bounded wait. (with-mutex (*a-mutex*) (format t "Thread ~A got the lock~%" *current-thread*) (sleep (random 5))) - (format t "Thread ~A dropped lock, dying now~%" *current-thread*))) + (format t "Thread ~A dropped lock, dying now~%" *current-thread*)) (make-thread #'thread-fn) (make-thread #'thread-fn) - @end lisp +@include struct-sb-thread-mutex.texinfo +@include fun-sb-thread-make-mutex.texinfo +@include fun-sb-thread-mutex-name.texinfo +@include fun-sb-thread-mutex-value.texinfo +@include fun-sb-thread-get-mutex.texinfo +@include fun-sb-thread-release-mutex.texinfo +@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-wait-on-semaphore.texinfo + @node Waitqueue/condition variables @comment node-name, next, previous, up @section Waitqueue/condition variables @@ -84,29 +141,29 @@ when you weren't expecting it to. 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 @@ -128,7 +185,7 @@ it. (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 () @@ -136,17 +193,23 @@ it. (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-make-waitqueue.texinfo +@include fun-sb-thread-waitqueue-name.texinfo +@include fun-sb-thread-condition-wait.texinfo +@include fun-sb-thread-condition-notify.texinfo +@include fun-sb-thread-condition-broadcast.texinfo + @node Sessions/Debugging @comment node-name, next, previous, up @section Sessions/Debugging @@ -158,7 +221,7 @@ view has its own collection of foreground/background/stopped threads. 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 @@ -177,20 +240,17 @@ leaves other sessions running. @node Implementation (Linux x86) @comment node-name, next, previous, up -@section Implementation (Linux x86) - -On Linux x86, threading is implemented using @code{clone()} and does -not involve pthreads. This is not because there is anything wrong -with pthreads @emph{per se}, but there is plenty wrong (from our -perspective) with LinuxThreads. SBCL threads are mapped 1:1 onto -Linux tasks which share a VM but nothing else - each has its own -process id and can be seen in e.g. @command{ps} output. - -Per-thread local bindings for special variables is achieved using the -%fs segment register to point to a per-thread storage area. This may -cause interesting results if you link to foreign code that expects -threading or creates new threads, and the thread library in question -uses %fs in an incompatible way. +@section Implementation (Linux x86/x86-64) + +Threading is implemented using pthreads and some Linux specific bits +like futexes. + +On x86 the per-thread local bindings for special variables is achieved +using the %fs segment register to point to a per-thread storage area. +This may cause interesting results if you link to foreign code that +expects threading or creates new threads, and the thread library in +question uses %fs in an incompatible way. On x86-64 the r12 register +has a similar role. Queues require the @code{sys_futex()} system call to be available: this is the reason for the NPTL requirement. We test at runtime that