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pthread_setcanceltype(3) [osf1 man page]

pthread_setcanceltype(3)				     Library Functions Manual					  pthread_setcanceltype(3)

NAME
pthread_setcanceltype - Sets the current thread's cancelability type. LIBRARY
DECthreads POSIX 1003.1c Library (libpthread.so) SYNOPSIS
#include <pthread.h> int pthread_setcanceltype( int type, int *oldtype); STANDARDS
Interfaces documented on this reference page conform to industry standards as follows: IEEE Std 1003.1c-1995, POSIX System Application Program Interface PARAMETERS
The cancelability type to set for the calling thread. The following are valid values: PTHREAD_CANCEL_DEFERRED PTHREAD_CANCEL_ASYNCHRONOUS The previous cancelability type. DESCRIPTION
This routine sets the cancelability type and returns the previous type in oldtype. When the cancelability state is set to PTHREAD_CANCEL_DISABLE, (see pthread_setcancelstate), a cancel cannot be delivered to the thread, even if a cancelable routine is called or asynchronous cancelability type is enabled. When the cancelability state is set to PTHREAD_CANCEL_ENABLE, cancelability depends on the thread's cancelability type. If the thread's cancelability type is set to PTHREAD_CANCEL_DEFERRED, the thread can only receive a cancel at specific cancellation points (including con- dition waits, thread joins, and calls to pthread_testcancel.) If the thread's cancelability type is PTHREAD_CANCEL_ASYNCHRONOUS, the thread can be canceled at any point in its execution. When a thread is created, the default cancelability type is PTHREAD_CANCEL_DEFERRED. Warning If the asynchronous cancelability type is set, do not call any routine unless it is explicitly documented as safe to be called with the asynchronous cancelability type. Note that none of the general run-time libraries and none of the DECthreads libraries are safe except for pthread_setcanceltype, pthread_setcancelstate, and cma_alert_restore. The asynchronous cancelability type should only be used when you have a compute-bound section of code that carries no state and makes no routine calls. RETURN VALUES
On successful completion, this routine returns the previous cancelability type in oldtype. If an error condition occurs, this routine returns an integer value indicating the type of error. Possible return values are as follows: Successful completion. The specified type is not PTHREAD_CANCEL_DEFERRED or PTHREAD_CANCEL_ASYNCHRONOUS. ERRORS
None RELATED INFORMATION
Functions: pthread_cancel(3), pthread_setcancelstate(3), pthread_testcancel(3) Manuals: Guide to DECthreads and Programmer's Guide delim off pthread_setcanceltype(3)

Check Out this Related Man Page

PTHREAD_TESTCANCEL(3)					   BSD Library Functions Manual 				     PTHREAD_TESTCANCEL(3)

NAME
pthread_setcancelstate, pthread_setcanceltype, pthread_testcancel -- set cancelability state SYNOPSIS
#include <pthread.h> int pthread_setcancelstate(int state, int *oldstate); int pthread_setcanceltype(int type, int *oldtype); void pthread_testcancel(void); DESCRIPTION
The pthread_setcancelstate() function atomically both sets the calling thread's cancelability state to the indicated state and returns the previous cancelability state at the location referenced by oldstate. Legal values for state are PTHREAD_CANCEL_ENABLE and PTHREAD_CANCEL_DISABLE. The pthread_setcanceltype() function atomically both sets the calling thread's cancelability type to the indicated type and returns the pre- vious cancelability type at the location referenced by oldtype. Legal values for type are PTHREAD_CANCEL_DEFERRED and PTHREAD_CANCEL_ASYNCHRONOUS. The cancelability state and type of any newly created threads, including the thread in which main() was first invoked, are PTHREAD_CANCEL_ENABLE and PTHREAD_CANCEL_DEFERRED respectively. The pthread_testcancel() function creates a cancellation point in the calling thread. The pthread_testcancel() function has no effect if cancelability is disabled. Cancelability States The cancelability state of a thread determines the action taken upon receipt of a cancellation request. The thread may control cancellation in a number of ways. Each thread maintains its own ``cancelability state'' which may be encoded in two bits: Cancelability Enable When cancelability is PTHREAD_CANCEL_DISABLE, cancellation requests against the target thread are held pending. Cancelability Type When cancelability is enabled and the cancelability type is PTHREAD_CANCEL_ASYNCHRONOUS, new or pending cancellation requests may be acted upon at any time. When cancelability is enabled and the cancelability type is PTHREAD_CANCEL_DEFERRED, cancel- lation requests are held pending until a cancellation point (see below) is reached. If cancelability is disabled, the setting of the cancelability type has no immediate effect as all cancellation requests are held pending; however, once cancelability is enabled again the new type will be in effect. Cancellation Points Cancellation points will occur when a thread is executing the following functions: accept(), aio_suspend(), close(), connect(), creat(), fcntl(), fsync(), lockf(), msgrcv(), msgsnd(), msync(), nanosleep(), open(), pause(), poll(), pread(), pselect(), pthread_cond_timedwait(), pthread_cond_wait(), pthread_join(), pthread_testcancel(), pwrite(), read(), readv(), recv(), recvfrom(), recvmsg(), select(), sem_wait(), send(), sendmsg(), sendto(), sigpause(), sigsuspend(), sigwait(), sleep(), system(), tcdrain(), usleep(), wait(), waitpid(), write(), writev(). RETURN VALUES
If successful, the pthread_setcancelstate() and pthread_setcanceltype() functions will return zero. Otherwise, an error number shall be returned to indicate the error. The pthread_setcancelstate() and pthread_setcanceltype() functions are used to control the points at which a thread may be asynchronously canceled. For cancellation control to be usable in modular fashion, some rules must be followed. For purposes of this discussion, consider an object 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 cancela- bility, it is because the client doesn't want to have to worry about how to clean up if the thread is canceled while executing some sequence of actions. If an object is called in such a state and it enables cancelability and a cancellation request is pending for that thread, then the thread will be 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 cancela- bility state, on exit from an object that 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. ERRORS
The function pthread_setcancelstate() may fail with: [EINVAL] The specified state is not PTHREAD_CANCEL_ENABLE or PTHREAD_CANCEL_DISABLE. The function pthread_setcanceltype() may fail with: [EINVAL] The specified state is not PTHREAD_CANCEL_DEFERRED or PTHREAD_CANCEL_ASYNCHRONOUS. SEE ALSO
pthread_cancel(3) STANDARDS
pthread_testcancel() conforms to ISO/IEC 9945-1:1996 (``POSIX.1''). AUTHORS
This man page was written by David Leonard <d@openbsd.org> for the OpenBSD implementation of pthread_cancel(3). BSD
January 17, 1999 BSD

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