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<!-- Copyright (C) 2003 Red Hat, Inc.                                -->
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><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&nbsp;--&nbsp;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 &lt;cyg/kernel/kapi.h&gt;
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
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ALIGN="LEFT"
WIDTH="100%"><TABLE
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>

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1	28	unneback	`<!-- Copyright (C) 2003 Red Hat, Inc. -->`
2			`<!-- This material may be distributed only subject to the terms -->`
3			`<!-- and conditions set forth in the Open Publication License, v1.0 -->`
4			`<!-- or later (the latest version is presently available at -->`
5			`<!-- http://www.opencontent.org/openpub/). -->`
6			`<!-- Distribution of the work or derivative of the work in any -->`
7			`<!-- standard (paper) book form is prohibited unless prior -->`
8			`<!-- permission is obtained from the copyright holder. -->`
9			`<HTML`
10			`><HEAD`
11			`><TITLE`
12			`>Thread destructors</TITLE`
13			`><meta name="MSSmartTagsPreventParsing" content="TRUE">`
14			`<META`
15			`NAME="GENERATOR"`
16			`CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+`
17			`"><LINK`
18			`REL="HOME"`
19			`TITLE="eCos Reference Manual"`
20			`HREF="ecos-ref.html"><LINK`
21			`REL="UP"`
22			`TITLE="The eCos Kernel"`
23			`HREF="kernel.html"><LINK`
24			`REL="PREVIOUS"`
25			`TITLE="Per-thread data"`
26			`HREF="kernel-thread-data.html"><LINK`
27			`REL="NEXT"`
28			`TITLE="Exception handling"`
29			`HREF="kernel-exceptions.html"></HEAD`
30			`><BODY`
31			`CLASS="REFENTRY"`
32			`BGCOLOR="#FFFFFF"`
33			`TEXT="#000000"`
34			`LINK="#0000FF"`
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38			`CLASS="NAVHEADER"`
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44			`CELLSPACING="0"`
45			`><TR`
46			`><TH`
47			`COLSPAN="3"`
48			`ALIGN="center"`
49			`>eCos Reference Manual</TH`
50			`></TR`
51			`><TR`
52			`><TD`
53			`WIDTH="10%"`
54			`ALIGN="left"`
55			`VALIGN="bottom"`
56			`><A`
57			`HREF="kernel-thread-data.html"`
58			`ACCESSKEY="P"`
59			`>Prev</A`
60			`></TD`
61			`><TD`
62			`WIDTH="80%"`
63			`ALIGN="center"`
64			`VALIGN="bottom"`
65			`></TD`
66			`><TD`
67			`WIDTH="10%"`
68			`ALIGN="right"`
69			`VALIGN="bottom"`
70			`><A`
71			`HREF="kernel-exceptions.html"`
72			`ACCESSKEY="N"`
73			`>Next</A`
74			`></TD`
75			`></TR`
76			`></TABLE`
77			`><HR`
78			`ALIGN="LEFT"`
79			`WIDTH="100%"></DIV`
80			`><H1`
81			`><A`
82			`NAME="KERNEL-THREAD-DESTRUCTORS">Thread destructors</H1`
83			`><DIV`
84			`CLASS="REFNAMEDIV"`
85			`><A`
86			`NAME="AEN730"`
87			`></A`
88			`><H2`
89			`>Name</H2`
90			`>cyg_thread_add_destructor, cyg_thread_rem_destructor -- Call functions on thread termination</DIV`
91			`><DIV`
92			`CLASS="REFSYNOPSISDIV"`
93			`><A`
94			`NAME="AEN734"><H2`
95			`>Synopsis</H2`
96			`><DIV`
97			`CLASS="FUNCSYNOPSIS"`
98			`><A`
99			`NAME="AEN735"><P`
100			`></P`
101			`><TABLE`
102			`BORDER="5"`
103			`BGCOLOR="#E0E0F0"`
104			`WIDTH="70%"`
105			`><TR`
106			`><TD`
107			`><PRE`
108			`CLASS="FUNCSYNOPSISINFO"`
109			`>#include <cyg/kernel/kapi.h>`
110			`typedef void (*<SPAN`
111			`CLASS="TYPE"`
112			`>cyg_thread_destructor_fn</SPAN`
113			`>)(<SPAN`
114			`CLASS="TYPE"`
115			`>cyg_addrword_t</SPAN`
116			`>);`
117			`</PRE`
118			`></TD`
119			`></TR`
120			`></TABLE`
121			`><P`
122			`><CODE`
123			`><CODE`
124			`CLASS="FUNCDEF"`
125			`>cyg_bool_t cyg_thread_add_destructor</CODE`
126			`>(cyg_thread_destructor_fn fn, cyg_addrword_t data);</CODE`
127			`></P`
128			`><P`
129			`><CODE`
130			`><CODE`
131			`CLASS="FUNCDEF"`
132			`>cyg_bool_t cyg_thread_rem_destructor</CODE`
133			`>(cyg_thread_destructor_fn fn, cyg_addrword_t data);</CODE`
134			`></P`
135			`><P`
136			`></P`
137			`></DIV`
138			`></DIV`
139			`><DIV`
140			`CLASS="REFSECT1"`
141			`><A`
142			`NAME="AEN753"`
143			`></A`
144			`><H2`
145			`>Description</H2`
146			`><P`
147			`>These functions are provided for cases when an application requires a`
148			`function to be automatically called when a thread exits. This is often`
149			`useful when, for example, freeing up resources allocated by the thread.`
150			`</P`
151			`><P`
152			`>This support must be enabled with the configuration option`
153			`<TT`
154			`CLASS="VARNAME"`
155			`>CYGPKG_KERNEL_THREADS_DESTRUCTORS</TT`
156			`>. When enabled,`
157			`you may register a function of type`
158			`<SPAN`
159			`CLASS="TYPE"`
160			`>cyg_thread_destructor_fn</SPAN`
161			`> to be called on thread`
162			`termination using <TT`
163			`CLASS="FUNCTION"`
164			`>cyg_thread_add_destructor</TT`
165			`>. You`
166			`may also provide it with a piece of arbitrary information in the`
167			`<TT`
168			`CLASS="PARAMETER"`
169			`><I`
170			`>data</I`
171			`></TT`
172			`> argument which will be passed to the`
173			`destructor function <TT`
174			`CLASS="PARAMETER"`
175			`><I`
176			`>fn</I`
177			`></TT`
178			`> when the thread`
179			`terminates. If you no longer wish to call a function previous`
180			`registered with <TT`
181			`CLASS="FUNCTION"`
182			`>cyg_thread_add_destructor</TT`
183			`>, you`
184			`may call <TT`
185			`CLASS="FUNCTION"`
186			`>cyg_thread_rem_destructor</TT`
187			`> with the same`
188			`parameters used to register the destructor function. Both these`
189			`functions return <TT`
190			`CLASS="LITERAL"`
191			`>true</TT`
192			`> on success and`
193			`<TT`
194			`CLASS="LITERAL"`
195			`>false</TT`
196			`> on failure.`
197			`</P`
198			`><P`
199			`>By default, thread destructors are per-thread, which means that registering`
200			`a destructor function only registers that function for the current thread.`
201			`In other words, each thread has its own list of destructors.`
202			`Alternatively you may disable the configuration option`
203			`<TT`
204			`CLASS="VARNAME"`
205			`>CYGSEM_KERNEL_THREADS_DESTRUCTORS_PER_THREAD</TT`
206			`> in which`
207			`case any registered destructors will be run when <SPAN`
208			`CLASS="emphasis"`
209			`><I`
210			`CLASS="EMPHASIS"`
211			`>any</I`
212			`></SPAN`
213			`>`
214			`threads exit. In other words, the thread destructor list is global and all`
215			`threads have the same destructors.`
216			`</P`
217			`><P`
218			`>There is a limit to the number of destructors which may be registered,`
219			`which can be controlled with the`
220			`<TT`
221			`CLASS="VARNAME"`
222			`>CYGNUM_KERNEL_THREADS_DESTRUCTORS</TT`
223			`> configuration`
224			`option. Increasing this value will very slightly increase the amount`
225			`of memory in use, and when`
226			`<TT`
227			`CLASS="VARNAME"`
228			`>CYGSEM_KERNEL_THREADS_DESTRUCTORS_PER_THREAD</TT`
229			`> is`
230			`enabled, the amount of memory used per thread will increase. When the`
231			`limit has been reached, <TT`
232			`CLASS="FUNCTION"`
233			`>cyg_thread_add_destructor</TT`
234			`>`
235			`will return <TT`
236			`CLASS="LITERAL"`
237			`>false</TT`
238			`>.`
239			`</P`
240			`></DIV`
241			`><DIV`
242			`CLASS="REFSECT1"`
243			`><A`
244			`NAME="KERNEL-THREAD-DESTRUCTORS-CONTEXT"`
245			`></A`
246			`><H2`
247			`>Valid contexts</H2`
248			`><P`
249			`>When <TT`
250			`CLASS="VARNAME"`
251			`>CYGSEM_KERNEL_THREADS_DESTRUCTORS_PER_THREAD</TT`
252			`>`
253			`is enabled, these functions must only be called from a thread context`
254			`as they implicitly operate on the current thread. When`
255			`<TT`
256			`CLASS="VARNAME"`
257			`>CYGSEM_KERNEL_THREADS_DESTRUCTORS_PER_THREAD</TT`
258			`> is`
259			`disabled, these functions may be called from thread or DSR context,`
260			`or at initialization time.`
261			`</P`
262			`></DIV`
263			`><DIV`
264			`CLASS="NAVFOOTER"`
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278			`><A`
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289			`ACCESSKEY="H"`
290			`>Home</A`
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299			`>Next</A`
300			`></TD`
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302			`><TR`
303			`><TD`
304			`WIDTH="33%"`
305			`ALIGN="left"`
306			`VALIGN="top"`
307			`>Per-thread data</TD`
308			`><TD`
309			`WIDTH="34%"`
310			`ALIGN="center"`
311			`VALIGN="top"`
312			`><A`
313			`HREF="kernel.html"`
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315			`>Up</A`
316			`></TD`
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320			`VALIGN="top"`
321			`>Exception handling</TD`
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326			`></HTML`
327			`>`

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