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<!-- Copyright (C) 2003 Red Hat, Inc. --> <!-- This material may be distributed only subject to the terms --> <!-- and conditions set forth in the Open Publication License, v1.0 --> <!-- or later (the latest version is presently available at --> <!-- http://www.opencontent.org/openpub/). --> <!-- Distribution of the work or derivative of the work in any --> <!-- standard (paper) book form is prohibited unless prior --> <!-- permission is obtained from the copyright holder. --> <HTML ><HEAD ><TITLE >Thread destructors</TITLE ><meta name="MSSmartTagsPreventParsing" content="TRUE"> <META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ "><LINK REL="HOME" TITLE="eCos Reference Manual" HREF="ecos-ref.html"><LINK REL="UP" TITLE="The eCos Kernel" HREF="kernel.html"><LINK REL="PREVIOUS" TITLE="Per-thread data" HREF="kernel-thread-data.html"><LINK REL="NEXT" TITLE="Exception handling" HREF="kernel-exceptions.html"></HEAD ><BODY CLASS="REFENTRY" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >eCos Reference Manual</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="kernel-thread-data.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="kernel-exceptions.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><H1 ><A NAME="KERNEL-THREAD-DESTRUCTORS">Thread destructors</H1 ><DIV CLASS="REFNAMEDIV" ><A NAME="AEN730" ></A ><H2 >Name</H2 >cyg_thread_add_destructor, cyg_thread_rem_destructor -- Call functions on thread termination</DIV ><DIV CLASS="REFSYNOPSISDIV" ><A NAME="AEN734"><H2 >Synopsis</H2 ><DIV CLASS="FUNCSYNOPSIS" ><A NAME="AEN735"><P ></P ><TABLE BORDER="5" BGCOLOR="#E0E0F0" WIDTH="70%" ><TR ><TD ><PRE CLASS="FUNCSYNOPSISINFO" >#include <cyg/kernel/kapi.h> typedef void (*<SPAN CLASS="TYPE" >cyg_thread_destructor_fn</SPAN >)(<SPAN CLASS="TYPE" >cyg_addrword_t</SPAN >); </PRE ></TD ></TR ></TABLE ><P ><CODE ><CODE CLASS="FUNCDEF" >cyg_bool_t cyg_thread_add_destructor</CODE >(cyg_thread_destructor_fn fn, cyg_addrword_t data);</CODE ></P ><P ><CODE ><CODE CLASS="FUNCDEF" >cyg_bool_t cyg_thread_rem_destructor</CODE >(cyg_thread_destructor_fn fn, cyg_addrword_t data);</CODE ></P ><P ></P ></DIV ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN753" ></A ><H2 >Description</H2 ><P >These functions are provided for cases when an application requires a function to be automatically called when a thread exits. This is often useful when, for example, freeing up resources allocated by the thread. </P ><P >This support must be enabled with the configuration option <TT CLASS="VARNAME" >CYGPKG_KERNEL_THREADS_DESTRUCTORS</TT >. When enabled, you may register a function of type <SPAN CLASS="TYPE" >cyg_thread_destructor_fn</SPAN > to be called on thread termination using <TT CLASS="FUNCTION" >cyg_thread_add_destructor</TT >. You may also provide it with a piece of arbitrary information in the <TT CLASS="PARAMETER" ><I >data</I ></TT > argument which will be passed to the destructor function <TT CLASS="PARAMETER" ><I >fn</I ></TT > when the thread terminates. If you no longer wish to call a function previous registered with <TT CLASS="FUNCTION" >cyg_thread_add_destructor</TT >, you may call <TT CLASS="FUNCTION" >cyg_thread_rem_destructor</TT > with the same parameters used to register the destructor function. Both these functions return <TT CLASS="LITERAL" >true</TT > on success and <TT CLASS="LITERAL" >false</TT > on failure. </P ><P >By default, thread destructors are per-thread, which means that registering a destructor function only registers that function for the current thread. In other words, each thread has its own list of destructors. Alternatively you may disable the configuration option <TT CLASS="VARNAME" >CYGSEM_KERNEL_THREADS_DESTRUCTORS_PER_THREAD</TT > in which case any registered destructors will be run when <SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >any</I ></SPAN > threads exit. In other words, the thread destructor list is global and all threads have the same destructors. </P ><P >There is a limit to the number of destructors which may be registered, which can be controlled with the <TT CLASS="VARNAME" >CYGNUM_KERNEL_THREADS_DESTRUCTORS</TT > configuration option. Increasing this value will very slightly increase the amount of memory in use, and when <TT CLASS="VARNAME" >CYGSEM_KERNEL_THREADS_DESTRUCTORS_PER_THREAD</TT > is enabled, the amount of memory used per thread will increase. When the limit has been reached, <TT CLASS="FUNCTION" >cyg_thread_add_destructor</TT > will return <TT CLASS="LITERAL" >false</TT >. </P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="KERNEL-THREAD-DESTRUCTORS-CONTEXT" ></A ><H2 >Valid contexts</H2 ><P >When <TT CLASS="VARNAME" >CYGSEM_KERNEL_THREADS_DESTRUCTORS_PER_THREAD</TT > is enabled, these functions must only be called from a thread context as they implicitly operate on the current thread. When <TT CLASS="VARNAME" >CYGSEM_KERNEL_THREADS_DESTRUCTORS_PER_THREAD</TT > is disabled, these functions may be called from thread or DSR context, or at initialization time. </P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="kernel-thread-data.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="ecos-ref.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="kernel-exceptions.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Per-thread data</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="kernel.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Exception handling</TD ></TR ></TABLE ></DIV ></BODY ></HTML >
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