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doc: Update "Multi-Threading" node.

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* doc/ref/libguile-concepts.texi (Multi-Threading): Remove bits about
  the requirement not to block in guile mode.
This commit is contained in:
Ludovic Courtès 2010-03-14 23:37:00 +01:00
parent d3b5628c6d
commit deec8986ff
1 changed files with 10 additions and 16 deletions
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26
doc/ref/libguile-concepts.texi
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@ -1,6 +1,6 @@
@c -*-texinfo-*-
@c This is part of the GNU Guile Reference Manual.
@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2005
@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2005, 2010
@c Free Software Foundation, Inc.
@c See the file guile.texi for copying conditions.
@ -450,21 +450,15 @@ that are stored in local variables. When a thread puts itself into
guile mode for the first time, it gets a Scheme representation and is
listed by @code{all-threads}, for example.
While in guile mode, a thread promises to reach a safe point
reasonably frequently (@pxref{Asynchronous Signals}). In addition to
running signal handlers, these points are also potential rendezvous
points of all guile mode threads where Guile can orchestrate global
things like garbage collection. Consequently, when a thread in guile
mode blocks and does no longer frequent safe points, it might cause
all other guile mode threads to block as well. To prevent this from
happening, a guile mode thread should either only block in libguile
functions (who know how to do it right), or should temporarily leave
guile mode with @code{scm_without_guile}.
For some common blocking operations, Guile provides convenience
functions. For example, if you want to lock a pthread mutex while in
guile mode, you might want to use @code{scm_pthread_mutex_lock} which is
just like @code{pthread_mutex_lock} except that it leaves guile mode
Threads in guile mode can block (e.g., do blocking I/O) without causing any
problems@footnote{In Guile 1.8, a thread blocking in guile mode would prevent
garbage collection to occur. Thus, threads had to leave guile mode whenever
they could block. This is no longer needed with Guile 2.0.}; temporarily
leaving guile mode with @code{scm_without_guile} before blocking slightly
improves GC performance, though. For some common blocking operations, Guile
provides convenience functions. For example, if you want to lock a pthread
mutex while in guile mode, you might want to use @code{scm_pthread_mutex_lock}
which is just like @code{pthread_mutex_lock} except that it leaves guile mode
while blocking.