glibc/linuxthreads/man/pthread_cancel.man

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LinuxThreads library. 1998-03-11 00:42 Wolfram Gloger <wmglo@dent.med.uni-muenchen.de> * linuxthreads/manager.c: Enable resetting of the thread scheduling policy to SCHED_OTHER when the parent thread has a different one. 1998-02-01 13:51 Ulrich Drepper <drepper@cygnus.com> * sysdeps/unix/sysv/linux/bits/posix_opt.h: Define _POSIX_ASYNCHRONOUS_IO. * sysdeps/pthread/pthread.h: Define bits for Unix98 variants of mutexes. * mutex.c: Implement new mutex types. * internals.h: Include <signal.h>. * libpthread.map: Add __erno_location and __h_errno_location. * errno.c: Return pointer to variable actually in use. This might not be the one in the thread structure. * internals.h (struct _pthread_descr_struct): Add new fields p_errnop and p_h_errnop. * manager.c (__pthread_manager): Set p_errnop and p_h_errnop member of manager thread structure. (pthread_handle_create): Set p_errnop and p_h_errnop members for new thread. * pthread.c: Adapt initializer for thread structures. (__pthread_initial_thread): Set p_errnop and p_h_errnop member. (__pthread_reset_main_thread): Reset p_errnop and p_h_errnop of current thread to global variables. 1998-01-31 17:27 Ulrich Drepper <drepper@cygnus.com> * rwlock.c: New file. * Makefile (libpthread-routines): Add rwlock. * sysdeps/pthread/pthread.h: Define data structures and declare functions. * libpthread.map: Add new functions. 1997-12-18 13:50 Philip Blundell <pb@nexus.co.uk> * sysdeps/arm/pt-machine.h: New file; add ARM support. * sysdeps/arm/Implies: likewise. * README: Document it. 1997-12-13 Andreas Schwab <schwab@issan.informatik.uni-dortmund.de> * signals.c: Remove unneeded initializer for sigwaited, saving a 1997-04-11 01:18 Andreas Schwab <schwab@issan.informatik.uni-dortmund.de> * semaphore.c (sem_init): Set sem_spinlock only if available. 1997-12-04 01:48 Ulrich Drepper <drepper@cygnus.com> * mutex.c: Implement PTHREAD_MUTEX_CHECKERROR. * sysdeps/pthread/pthread.h: Define PTHREAD_MUTEX_CHECKERROR. * Makefile: Update from LinuxThreads 0.7. * internals.h. Likewise. * manager.c: Likewise. * mutex.c: Likewise. * pthread.c: Likewise. * signals.c: Likewise. * specific.c: Likewise. * Examples/ex3.c: Likewise. 1997-11-20 18:13 Ulrich Drepper <drepper@cygnus.com> * pthread.c (__pthread_reset_main_thread): Close pipe only if still open. 1997-10-29 05:38 Ulrich Drepper <drepper@cygnus.com> * wrapsyscall.c: Add socket functions which are also cancelation points. 1997-10-19 21:40 Wolfram Gloger <wg@wolfram.dent.med.uni-muenchen.de> * specific.c (__libc_internal_tsd_set, __libc_internal_tsd_get): New functions for fast thread specific data within libc. * internals.h: Add new array p_libc_specific to struct _pthread_descr_struct. * sysdeps/pthread/bits/libc-lock.h: Declare new functions. 1997-10-13 05:39 Ulrich Drepper <drepper@cygnus.com> * semaphore.h: Add __BEGIN_DECLS/__END_DECLS. Reported by Ralf Corsepius <corsepiu@faw.uni-ulm.de>. 1997-08-29 03:05 Ulrich Drepper <drepper@cygnus.com> * internals.h (struct _pthread_descr_struct): Add definitions for two-level specific key handling. * manager.c (pthread_handle_create): Initialize specific memory array. * specific.c: Implement two-level key handling. * weaks.c: Don't provide dummy key handling. * sysdeps/pthread/bits/libc-lock.h: Typedef __libc_lock_t (no #define). Add definition of __libc_key_t. * sysdeps/unix/sysv/linux/bits/local_lim.h: Define PTHREAD_KEYS_MAX as 1024. Add definition of _POSIX_THREAD_DESTRUCTOR_ITERATIONS and PTHREAD_DESTRUCTOR_ITERATIONS. * manager.c (pthread_handle_create): Compare mmap result with MAP_FAILED. * ptfork.c: Rename to __pthread_atfork and make old name a weak alias. * sysdeps/pthread/bits/pthread.h: Add prototype for __pthread_atfork. 1997-08-22 19:04 Richard Henderson <rth@cygnus.com> sysdeps/sparc -> sysdeps/sparc/sparc32 sysdeps/sparc64 -> sysdeps/sparc/sparc64 * internals.h: Change definition of THREAD_SELF to be an expression, not a statement that did a return. * sysdeps/alpha/pt-machine.h (THREAD_SELF): Update accordingly. * sysdeps/sparc/sparc32/pt-machine.h (THREAD_SELF, INIT_THREAD_SELF): Follow Solaris and use a "system reserved" register (%g6) to hold the thread descriptor. * sysdeps/sparc/sparc64/pt-machine.h: Likewise. 1997-08-03 00:09 Ulrich Drepper <drepper@cygnus.com> * mutex.c: Correct pthread_once. Patch by Xavier Leroy. * sysdeps/pthread/pthread.h: Add prototype for __pthread_once. * sysdeps/pthread/bits/pthread.h: Add macros for __libc_once. * semaphore.c: Include spinlock.h only when needed. * specific.c (__pthread_setsepcific, __pthread_getspecific): Reject keys for entries not in use. * weaks.c: Implement key handling functions for real. 1997-06-29 01:04 Richard Henderson <richard@gnu.ai.mit.edu> Initial sparc64-linux support: * linuxthreads/sysdeps/sparc64/Implies: New file. * linuxthreads/sysdeps/sparc64/pt-machine.h: Likewise. 1997-06-29 00:48 Ulrich Drepper <drepper@cygnus.com> * semaphore.c: Include spinlock.h at correct place. Patch by HJ Lu. 1997-06-13 10:06 Richard Henderson <rth@tamu.edu> The Great Bit File Move: * sysdeps/alpha/semaphorebits.h: -> .../bits/semaphore.h. * sysdeps/powerpc/semaphorebits.h: Likewise. * sysdeps/pthread/cmpxchg/semaphorebits.h: Likewise. * sysdeps/pthread/no-cmpxchg/semaphorebits.h: Likewise. * sysdeps/pthread/libc-lock.h: -> bits/ * sysdeps/pthread/stdio-lock.h: Likewise. * sysdeps/unix/sysv/linux/local_lim.h: Likewise. * sysdeps/unix/sysv/linux/posix_opt.h: Likewise. * semaphore.h: Likewise. * sysdeps/pthread/pthread.h: Likewise. * lockfile.c: <foo.h> -> <bits/foo.h>. * semaphore.h: Likewise. * Makefile: (headers): foo.h -> bits/foo.h. * sysdeps/pthread/Makefile: Likewise. 1997-04-11 01:18 Andreas Schwab <schwab@issan.informatik.uni-dortmund.de> * semaphore.c (sem_init): Set sem_spinlock only if available. * sysdeps/m68k/pt-machine.h (testandset, __compare_and_swap): Fix asm constraints. 1997-04-09 03:00 Ulrich Drepper <drepper@cygnus.com> Update from LinuxThreads 0.6. * attr.c (pthread_attr_getdetachstate): Use __sched_get_priority_max and __sched_get_priority_min instead of names without `__'. * manager.c: Rewrite large parts to implement opaque pthread_t. * cancel.c: Adapt for opaque pthread_t type. * condvar.c: Likewise. * errno.c: Likewise. * join.c: Likewise. * mutex.c: Likewise. * pthread.c: Likewise. * signals.c: Likewise. * specific.c: Likewise. * restart.h: Likewise. * queue.h: Likewise. * Examples/ex3.c: Likewise. * Examples/ex4.c: Likewise. * sysdeps/pthread/pthread.h: Likewise. * pthread.c: Accumulate time for all threads in thread manager. * semaphore.c: Implement fallback implementation for architectures sometimes missing compare-exchange operations. * cancel.c (pthread_cancel): Validate handle argument. * join.c (pthread_join): Likewise. (pthread_detach): Likewise. * signals.c (pthread_kill): Likewise. * spinlock.h (acquire): Use __sched_yield not sched_yield. * queue.h (enqueue): Enqueue thread according to priority. * internals.c (struct pthread_start_args): New struct for passing args to cloning function. (struct _pthread): Rename to _pthread_descr_struct and adapt for opaque pthread_t. * Examples/Makefile (clean): Pass -f option to rm. * sysdeps/i386/pt-machine.h: Add check for compare-exchange instruction and define TEST_FOR_COMPARE_AND_SWAP. * sysdeps/i386/i486/pt-machine.h: Removed. * sysdeps/unix/sysv/linux/local_lim.h (PTHREAD_THREADS_MAX): Increase to 1024. 1997-04-04 16:38 Ulrich Drepper <drepper@cygnus.com> * restart.h (suspend): Clear p_signal before suspending. (suspend_with_cancellation): Likewise. Patch by Xavier Leroy <Xavier.Leroy@inria.fr>. * weaks.c: Make __pthread_key_create return 1. * sysdeps/pthread/libc-lock.h: Define __libc_key_create, __libc_getspecific, __libc_setspecific, and __libc_key_t. * sysdeps/pthread/stdio-lock.h: Don't care for implementation not using libio. 1997-03-19 15:13 Miguel de Icaza <miguel@nuclecu.unam.mx> * sysdeps/sparc/pt-machine (RELEASE): Fix. 1997-03-01 07:55 Geoff Keating <geoffk@ozemail.com.au> * sysdeps/powerpc/Implies: Added. * sysdeps/powerpc/pt-machine.h: Added. * sysdeps/powerpc/semaphorebits.h: Added. 1997-01-22 01:22 Ulrich Drepper <drepper@cygnus.com> * linuxtheads/pthread.c (__pthread_initial_thread): Correct initializer. (__pthread_manager_thread): Likewise. Reported by Andreas Jaeger. 1997-01-18 22:15 Richard Henderson <rth@tamu.edu> Since sigset_t no longer fits in a register, we can't pass in the thread's initial mask so easily. Take this opportunity to simplify the clone implementation by only accepting a single void* argument. * linuxthreads/manager.c (__pthread_manager): Put thread vitals in the thread struct instead of as arguments through clone. (pthread_start_thread): Look for them there. * linuxthreads/internals.h (struct _pthread): Add p_initial_fn, p_initial_fn_arg, p_initial_mask. Fix __pthread_manager proto. * linuxthreads/pthread.c (pthread_initialize_manager): Revise clone invocation.
1998-03-11 20:42:25 +08:00
.TH PTHREAD_CANCEL 3 LinuxThreads
.XREF pthread_setcancelstate
.XREF pthread_setcanceltype
.XREF pthread_testcancel
.SH NAME
pthread_cancel, pthread_setcancelstate, pthread_setcanceltype, pthread_testcancel \- thread cancellation
.SH SYNOPSIS
#include <pthread.h>
int pthread_cancel(pthread_t thread);
int pthread_setcancelstate(int state, int *oldstate);
int pthread_setcanceltype(int type, int *oldtype);
void pthread_testcancel(void);
.SH DESCRIPTION
Cancellation is the mechanism by which a thread can terminate the
execution of another thread. More precisely, a thread can send a
cancellation request to another thread. Depending on its settings, the
target thread can then either ignore the request, honor it
immediately, or defer it till it reaches a cancellation point.
When a thread eventually honors a cancellation request, it performs as
if !pthread_exit(PTHREAD_CANCELED)! has been called at that point:
all cleanup handlers are executed in reverse order, finalization
functions for thread-specific data are called, and finally the thread
stops executing with the return value !PTHREAD_CANCELED!. See
!pthread_exit!(3) for more information.
!pthread_cancel! sends a cancellation request to the thread denoted
by the |thread| argument.
!pthread_setcancelstate! changes the cancellation state for the
calling thread -- that is, whether cancellation requests are ignored
or not. The |state| argument is the new cancellation state: either
!PTHREAD_CANCEL_ENABLE! to enable cancellation, or
!PTHREAD_CANCEL_DISABLE! to disable cancellation (cancellation
requests are ignored). If |oldstate| is not !NULL!, the previous
cancellation state is stored in the location pointed to by |oldstate|,
and can thus be restored later by another call to
!pthread_setcancelstate!.
!pthread_setcanceltype! changes the type of responses to cancellation
requests for the calling thread: asynchronous (immediate) or deferred.
The |type| argument is the new cancellation type: either
!PTHREAD_CANCEL_ASYNCHRONOUS! to cancel the calling thread as soon as
the cancellation request is received, or !PTHREAD_CANCEL_DEFERRED! to
keep the cancellation request pending until the next cancellation
point. If |oldtype| is not !NULL!, the previous
cancellation state is stored in the location pointed to by |oldtype|,
and can thus be restored later by another call to
!pthread_setcanceltype!.
Threads are always created by !pthread_create!(3) with cancellation
enabled and deferred. That is, the initial cancellation state is
!PTHREAD_CANCEL_ENABLE! and the initial type is
!PTHREAD_CANCEL_DEFERRED!.
Cancellation points are those points in the program execution where a
test for pending cancellation requests is performed and cancellation
is executed if positive. The following POSIX threads functions
are cancellation points:
!pthread_join!(3)
.br
!pthread_cond_wait!(3)
.br
!pthread_cond_timedwait!(3)
.br
!pthread_testcancel!(3)
.br
!sem_wait!(3)
.br
!sigwait!(3)
All other POSIX threads functions are guaranteed not to be
cancellation points. That is, they never perform cancellation in
deferred cancellation mode.
!pthread_testcancel! does nothing except testing for pending
cancellation and executing it. Its purpose is to introduce explicit
checks for cancellation in long sequences of code that do not call
cancellation point functions otherwise.
.SH "RETURN VALUE"
!pthread_cancel!, !pthread_setcancelstate! and
!pthread_setcanceltype! return 0 on success and a non-zero error code
on error.
.SH ERRORS
!pthread_cancel! returns the following error code on error:
.RS
.TP
!ESRCH!
no thread could be found corresponding to that specified by the |thread| ID.
.RE
!pthread_setcancelstate! returns the following error code on error:
.RS
.TP
!EINVAL!
the |state| argument is not !PTHREAD_CANCEL_ENABLE! nor
!PTHREAD_CANCEL_DISABLE!
.RE
!pthread_setcanceltype! returns the following error code on error:
.RS
.TP
!EINVAL!
the |type| argument is not !PTHREAD_CANCEL_DEFERRED! nor
!PTHREAD_CANCEL_ASYNCHRONOUS!
.RE
.SH AUTHOR
Xavier Leroy <Xavier.Leroy@inria.fr>
.SH "SEE ALSO"
!pthread_exit!(3),
!pthread_cleanup_push!(3),
!pthread_cleanup_pop!(3).
.SH BUGS
POSIX specifies that a number of system calls (basically, all
system calls that may block, such as !read!(2), !write!(2), !wait!(2),
etc.) and library functions that may call these system calls (e.g.
!fprintf!(3)) are cancellation points. LinuxThreads is not yet
integrated enough with the C library to implement this, and thus none
of the C library functions is a cancellation point.
For system calls at least, there is a workaround. Cancellation
requests are transmitted to the target thread by sending it a
signal. That signal will interrupt all blocking system calls, causing
them to return immediately with the !EINTR! error. So, checking for
cancellation during a !read! system call, for instance, can be
achieved as follows:
.RS
.ft 3
.nf
.sp
pthread_testcancel();
retcode = read(fd, buffer, length);
pthread_testcancel();
.ft
.LP
.RE
.fi