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><A
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><A
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NAME="KERNEL-THREAD-TERMINATION">Thread termination</H1
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NAME="KERNEL-THREAD-TERMINATION">Thread termination</H1
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><DIV
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><DIV
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CLASS="REFNAMEDIV"
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CLASS="REFNAMEDIV"
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><A
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><A
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NAME="AEN560"
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NAME="AEN560"
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></A
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><H2
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><H2
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>Name</H2
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>Name</H2
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>cyg_thread_exit, cyg_thread_kill, cyg_thread_delete -- Allow threads to terminate</DIV
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>cyg_thread_exit, cyg_thread_kill, cyg_thread_delete -- Allow threads to terminate</DIV
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><DIV
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><DIV
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CLASS="REFSYNOPSISDIV"
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CLASS="REFSYNOPSISDIV"
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><A
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><A
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NAME="AEN565"><H2
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NAME="AEN565"><H2
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>Synopsis</H2
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>Synopsis</H2
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><DIV
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><DIV
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CLASS="FUNCSYNOPSIS"
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CLASS="FUNCSYNOPSIS"
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><A
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><A
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NAME="AEN566"><P
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NAME="AEN566"><P
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></P
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></P
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><TABLE
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><TD
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><PRE
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><PRE
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CLASS="FUNCSYNOPSISINFO"
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CLASS="FUNCSYNOPSISINFO"
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>#include <cyg/kernel/kapi.h>
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>#include <cyg/kernel/kapi.h>
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</PRE
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</PRE
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></TD
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></TD
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></TR
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></TR
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></TABLE
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></TABLE
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><P
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><P
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><CODE
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><CODE
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><CODE
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><CODE
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CLASS="FUNCDEF"
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CLASS="FUNCDEF"
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>void cyg_thread_exit</CODE
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>void cyg_thread_exit</CODE
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>(void);</CODE
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>(void);</CODE
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></P
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></P
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><P
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><P
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><CODE
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><CODE
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><CODE
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><CODE
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CLASS="FUNCDEF"
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CLASS="FUNCDEF"
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>void cyg_thread_kill</CODE
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>void cyg_thread_kill</CODE
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>(cyg_handle_t thread);</CODE
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>(cyg_handle_t thread);</CODE
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></P
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></P
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><P
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><P
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><CODE
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><CODE
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><CODE
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><CODE
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CLASS="FUNCDEF"
|
CLASS="FUNCDEF"
|
>void cyg_thread_delete</CODE
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>void cyg_thread_delete</CODE
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>(cyg_handle_t thread);</CODE
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>(cyg_handle_t thread);</CODE
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></P
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></P
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><P
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><P
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></P
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></P
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></DIV
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></DIV
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></DIV
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></DIV
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><DIV
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><DIV
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CLASS="REFSECT1"
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CLASS="REFSECT1"
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><A
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><A
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NAME="AEN582"
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NAME="AEN582"
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></A
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></A
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><H2
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><H2
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>Description</H2
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>Description</H2
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><P
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><P
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>In many embedded systems the various threads are allocated statically,
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>In many embedded systems the various threads are allocated statically,
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created during initialization, and never need to terminate. This
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created during initialization, and never need to terminate. This
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avoids any need for dynamic memory allocation or other resource
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avoids any need for dynamic memory allocation or other resource
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management facilities. However if a given application does have a
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management facilities. However if a given application does have a
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requirement that some threads be created dynamically, must terminate,
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requirement that some threads be created dynamically, must terminate,
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and their resources such as the stack be reclaimed, then the kernel
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and their resources such as the stack be reclaimed, then the kernel
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provides the functions <TT
|
provides the functions <TT
|
CLASS="FUNCTION"
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CLASS="FUNCTION"
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>cyg_thread_exit</TT
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>cyg_thread_exit</TT
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>,
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>,
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<TT
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<TT
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CLASS="FUNCTION"
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CLASS="FUNCTION"
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>cyg_thread_kill</TT
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>cyg_thread_kill</TT
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>, and
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>, and
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<TT
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<TT
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CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>cyg_thread_delete</TT
|
>cyg_thread_delete</TT
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>.
|
>.
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</P
|
</P
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><P
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><P
|
><TT
|
><TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>cyg_thread_exit</TT
|
>cyg_thread_exit</TT
|
> allows a thread to terminate
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> allows a thread to terminate
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itself, thus ensuring that it will not be run again by the scheduler.
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itself, thus ensuring that it will not be run again by the scheduler.
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However the <SPAN
|
However the <SPAN
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CLASS="STRUCTNAME"
|
CLASS="STRUCTNAME"
|
>cyg_thread</SPAN
|
>cyg_thread</SPAN
|
> data structure passed
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> data structure passed
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to <TT
|
to <TT
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CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>cyg_thread_create</TT
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>cyg_thread_create</TT
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> remains in use, and the
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> remains in use, and the
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handle returned by <TT
|
handle returned by <TT
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CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>cyg_thread_create</TT
|
>cyg_thread_create</TT
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> remains
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> remains
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valid. This allows other threads to perform certain operations on the
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valid. This allows other threads to perform certain operations on the
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terminated thread, for example to determine its stack usage via
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terminated thread, for example to determine its stack usage via
|
<TT
|
<TT
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CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>cyg_thread_measure_stack_usage</TT
|
>cyg_thread_measure_stack_usage</TT
|
>. When the handle
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>. When the handle
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and <SPAN
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and <SPAN
|
CLASS="STRUCTNAME"
|
CLASS="STRUCTNAME"
|
>cyg_thread</SPAN
|
>cyg_thread</SPAN
|
> structure are no longer
|
> structure are no longer
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required, <TT
|
required, <TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>cyg_thread_delete</TT
|
>cyg_thread_delete</TT
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> should be called to
|
> should be called to
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release these resources. If the stack was dynamically allocated then
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release these resources. If the stack was dynamically allocated then
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this should not be freed until after the call to
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this should not be freed until after the call to
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<TT
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<TT
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CLASS="FUNCTION"
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CLASS="FUNCTION"
|
>cyg_thread_delete</TT
|
>cyg_thread_delete</TT
|
>.
|
>.
|
</P
|
</P
|
><P
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><P
|
>Alternatively, one thread may use <TT
|
>Alternatively, one thread may use <TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>cyg_thread_kill</TT
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>cyg_thread_kill</TT
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>
|
>
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on another This has much the same effect as the affected thread
|
on another This has much the same effect as the affected thread
|
calling <TT
|
calling <TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>cyg_thread_exit</TT
|
>cyg_thread_exit</TT
|
>. However killing a thread
|
>. However killing a thread
|
is generally rather dangerous because no attempt is made to unlock any
|
is generally rather dangerous because no attempt is made to unlock any
|
synchronization primitives currently owned by that thread or release
|
synchronization primitives currently owned by that thread or release
|
any other resources that thread may have claimed. Therefore use of
|
any other resources that thread may have claimed. Therefore use of
|
this function should be avoided, and
|
this function should be avoided, and
|
<TT
|
<TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>cyg_thread_exit</TT
|
>cyg_thread_exit</TT
|
> is preferred.
|
> is preferred.
|
<TT
|
<TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>cyg_thread_kill</TT
|
>cyg_thread_kill</TT
|
> cannot be used by a thread to
|
> cannot be used by a thread to
|
kill itself.
|
kill itself.
|
</P
|
</P
|
><P
|
><P
|
><TT
|
><TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>cyg_thread_delete</TT
|
>cyg_thread_delete</TT
|
> should be used on a thread
|
> should be used on a thread
|
after it has exited and is no longer required. After this call the
|
after it has exited and is no longer required. After this call the
|
thread handle is no longer valid, and both the
|
thread handle is no longer valid, and both the
|
<SPAN
|
<SPAN
|
CLASS="STRUCTNAME"
|
CLASS="STRUCTNAME"
|
>cyg_thread</SPAN
|
>cyg_thread</SPAN
|
> structure and the thread stack can
|
> structure and the thread stack can
|
be re-used or freed. If <TT
|
be re-used or freed. If <TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>cyg_thread_delete</TT
|
>cyg_thread_delete</TT
|
> is
|
> is
|
invoked on a thread that is still running then there is an implicit
|
invoked on a thread that is still running then there is an implicit
|
call to <TT
|
call to <TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>cyg_thread_kill</TT
|
>cyg_thread_kill</TT
|
>.
|
>.
|
</P
|
</P
|
></DIV
|
></DIV
|
><DIV
|
><DIV
|
CLASS="REFSECT1"
|
CLASS="REFSECT1"
|
><A
|
><A
|
NAME="KERNEL-THREAD-TERMINATION-CONTEXT"
|
NAME="KERNEL-THREAD-TERMINATION-CONTEXT"
|
></A
|
></A
|
><H2
|
><H2
|
>Valid contexts</H2
|
>Valid contexts</H2
|
><P
|
><P
|
><TT
|
><TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>cyg_thread_exit</TT
|
>cyg_thread_exit</TT
|
>,
|
>,
|
<TT
|
<TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>cyg_thread_kill</TT
|
>cyg_thread_kill</TT
|
> and
|
> and
|
<TT
|
<TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>cyg_thread_delete</TT
|
>cyg_thread_delete</TT
|
> can only be called from thread
|
> can only be called from thread
|
context.
|
context.
|
</P
|
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