Man Pthread_setcanceltype en anglais
PTHREAD_SETCANCELSTATE(P)  POSIX Programmer's Manual PTHREAD_SETCANCELSTATE(P)



 

NAME


       pthread_setcancelstate, pthread_setcanceltype, pthread_testcancel - set
       cancelability state

 

SYNOPSIS


       #include 

       int pthread_setcancelstate(int state, int *oldstate);
       int pthread_setcanceltype(int type, int *oldtype);
       void pthread_testcancel(void);


 

DESCRIPTION






       The pthread_setcancelstate() function shall  atomically  both  set  the
       calling  thread's cancelability state to the indicated state and return
       the previous cancelability state at the  location  referenced  by  old-
       state.   Legal   values   for   state   are  PTHREAD_CANCEL_ENABLE  and
       PTHREAD_CANCEL_DISABLE.

       The pthread_setcanceltype() function  shall  atomically  both  set  the
       calling  thread's  cancelability  type to the indicated type and return
       the previous cancelability type at the location referenced by  oldtype.
       Legal  values  for  type  are  PTHREAD_CANCEL_DEFERRED and PTHREAD_CAN-
       CEL_ASYNCHRONOUS.

       The cancelability state and type of any newly created threads,  includ-
       ing the thread in which main() was first invoked, shall be PTHREAD_CAN-
       CEL_ENABLE and PTHREAD_CANCEL_DEFERRED respectively.

       The pthread_testcancel() function shall create a cancellation point  in
       the  calling  thread.  The  pthread_testcancel() function shall have no
       effect if cancelability is disabled.

 

RETURN VALUE


       If successful, the pthread_setcancelstate() and pthread_setcanceltype()
       functions  shall  return  zero;  otherwise,  an  error  number shall be
       returned to indicate the error.

 

ERRORS


       The pthread_setcancelstate() function may fail if:

       EINVAL The specified state is not PTHREAD_CANCEL_ENABLE or PTHREAD_CAN-
              CEL_DISABLE.


       The pthread_setcanceltype() function may fail if:

       EINVAL The   specified   type   is   not   PTHREAD_CANCEL_DEFERRED   or
              PTHREAD_CANCEL_ASYNCHRONOUS.


       These functions shall not return an error code of [EINTR].

       The following sections are informative.

 

EXAMPLES


       None.

 

APPLICATION USAGE


       None.

 

RATIONALE


       The pthread_setcancelstate() and pthread_setcanceltype() functions con-
       trol  the  points at which a thread may be asynchronously canceled. For
       cancellation control to be usable in modular fashion, some  rules  need
       to be followed.

       An  object can be considered to be a generalization of a procedure.  It
       is a set of procedures and global  variables  written  as  a  unit  and
       called  by clients not known by the object. Objects may depend on other
       objects.

       First, cancelability should only be disabled on  entry  to  an  object,
       never  explicitly  enabled.  On  exit from an object, the cancelability
       state should always be restored to its value on entry to the object.

       This follows from a modularity argument: if the client of an object (or
       the client of an object that uses that object) has disabled cancelabil-
       ity, it is because the client does  not  want  to  be  concerned  about
       cleaning  up if the thread is canceled while executing some sequence of
       actions. If an object is called in such a state and it enables cancela-
       bility  and a cancellation request is pending for that thread, then the
       thread is canceled, contrary to the wish of the client that disabled.

       Second, the cancelability type may be explicitly set to either deferred
       or asynchronous upon entry to an object.  But as with the cancelability
       state, on exit from an object the cancelability type should  always  be
       restored to its value on entry to the object.

       Finally,  only  functions  that  are  cancel-safe  may be called from a
       thread that is asynchronously cancelable.

 

FUTURE DIRECTIONS


       None.

 

SEE ALSO


       pthread_cancel() , the Base Definitions volume of IEEE Std 1003.1-2001,
       

 

COPYRIGHT


       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained  online
       at http://www.opengroup.org/unix/online.html .



IEEE/The Open Group                  2003            PTHREAD_SETCANCELSTATE(P)