pthread_cancel






pthread_cancel — stop and cancel a thread (not recommended)



     #include <rtl_signal.h>
#include <rtl_sched.h>

int pthread_cancel(pthread_t thread);



     This function is a standard POSIX threads function and is one of the weaker
parts of the POSIX threads specification. The idea is that pthread_cancel will
request termination of the target thread and this termination will either take
place asynchronously or will be ignored depending on the cancel state of the
target thread. If the target thread is in a DISABLED state, cancel will be
pended until the thread goes to an ENABLED state. If the target thread has
ENABLED it will either be in a DEFERRED or ASYNCHRONOUS mode. DEFERRED mode will
defer the cancel until the thread is in a cancel point (one of a set of POSIX
specified functions that correspond to states where the thread is sleeping). And
so on. The semantics are complicated.  Note that canceling a thread on a
different processor is not supported in RTLinux.

     Cancel has a bizzare effect on a thread. If the thread is accepting the
cancel, it will execute whatever cancel handlers it has pushed using
pthread_cleanup_push. However a canceled thread holding a mutex is not forced to
cleanup the mutex lock and, in general, a canceled thread may leave a terrible
mess behind. Our recommendation is to avoid the use of this function as if it
were designed by a committee of software consultants rubbing their hands with
glee at the huge consulting fees they would get coming in to rescue your project
after the use of pthread_cancel has totally randomized the operation of your
code. If cancel was not a required part of POSIX spec, we would not inflict  it
on our poor abused operating system.  Forgive us.



     pthread_cancel returns 0 on success and a non‐zero error code on error.



     We have yet to see a good reason to use this function.

ESRCH     No thread could be found corresponding to that specified by the given
          thread ID.



     Victor Yodaiken (support@fsmlabs.com (link to URL
mailto:support@fsmlabs.com) )



     pthread_cancel is safe to call from thread, and from Linux kernel code. It
is not safe to call from interrupt code.









                                       ‐2‐


pthread_setcancelstate(3), pthread_testcancel(3)

     ©2001 FSMLabs Inc.

     All rights reserved.