Comtrol eCos - Manual (Page 55)

Thread destructors
Name
cyg_thread_add_destructor, cyg_thread_rem_destructor — Call functions on thread
termination
Synopsis
#include < cyg/kernel/kapi.h >
typedef void (*cyg_thread_destructor_fn)(cyg_addrword_t);
cyg_bool_t cyg_thread_add_destructor(cyg_thread_destructor_fn fn, cyg_addrword_t data);
cyg_bool_t cyg_thread_rem_destructor(cyg_thread_destructor_fn fn, cyg_addrword_t data);
Description
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.
This support must be enabled with the configuration option CYGPKG_KERNEL_THREADS_DESTRUCTORS . When en-
abled, you may register a function of type cyg_thread_destructor_fn to be called on thread termination using
cyg_thread_add_destructor . You may also provide it with a piece of arbitrary information in the data argu-
ment which will be passed to the destructor function fn when the thread terminates. If you no longer wish to call a
function previous registered with cyg_thread_add_destructor , you may call cyg_thread_rem_destructor
with the same parameters used to register the destructor function. Both these functions return true on success and
false on failure.
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
CYGSEM_KERNEL_THREADS_DESTRUCTORS_PER_THREAD in which case any
registered destructors will be run when any threads exit. In other words, the thread destructor list is global and all
threads have the same destructors.
There is a limit to the number of destructors which may be registered, which can be controlled with the
CYGNUM_KERNEL_THREADS_DESTRUCTORS configuration option. Increasing this value will very slightly
increase the amount of memory in use, and when CYGSEM_KERNEL_THREADS_DESTRUCTORS_PER_THREAD
is enabled, the amount of memory used per thread will increase. When the limit has been reached,
cyg_thread_add_destructor will return false .
Valid contexts
When CYGSEM_KERNEL_THREADS_DESTRUCTORS_PER_THREAD is enabled, these functions must
only be called from a thread context as they implicitly operate on the current thread. When
CYGSEM_KERNEL_THREADS_DESTRUCTORS_PER_THREAD is disabled, these functions may be called from thread
or DSR context, or at initialization time.
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