Книга: Programming with POSIX® Threads
10.1.6 Cancellation points
10.1.6 Cancellation points
Most UNIX systems support a substantial number of interfaces that do not come from POSIX. The select and poll interfaces, for example, should be deferred cancellation points. Pthreads did not require these functions to be cancellation points, however, because they do not exist within POSIX. 1.
The select and poll functions, however, along with many others, exist in X/Open. The XSH5 standard includes an expanded list of cancellation points covering X/Open interfaces.
Additional functions that must be cancellation points in XSH5:
getmsg pread sigpause
getpmsg putmsg usleep
lockf putpmsg wait3
msgrcv pwrite waitid
msgsnd readv writev
poll select
Additional functions that may be cancellation points in XSH5:
Condition variable wait clock:
int pthread_condattr_getclock (
const pthread_condattr_t *attr,
clockid_t *clock_id); int pthread_condattr_setclock (
pthread_condattr_t *attr,
clockid_t clock_id);
Barriers:
int barrier_attr_init (barrier_attr_t *attr); int barrier_attr_destroy (barrier_attr_t *attr); int barrier_attr_getpshared (
const barrier_attr_t *attr, int *pshared); int barrier_attr_setpshared (
barrier_attr_t *attr, int pshared); int barrier_init (barrier_t *barrier,
const barrier_attr_t *attr, int count); int barrier_destroy (barrier_t *barrier); int barrier_wait (barrier_t *barrier);
catclose
catgets
catopen
closelog
dbm_close
dbm_delete
dbm_fetch
dbm_nextkey
dbm_open
dbm_store
dlclose
dlopen
endgrent
endpwent
endutxent
fgetwc
fgetws
fputwc
fputws
fseeko
fsetpos
ftello
ftw
fwprintf
fwscanf
getgrent
getpwent
getutxent
getutxid
getutxline
getw
getwc
getwchar
iconv_close
iconv_open
ioctl
mkstemp
nftw
openlog
pclose
popen
pututxline
putw
putwc
putwchar
readdir_r
seekdir
semop
setgrent
setpwent
setutxent
syslog
ungetwc
vfprintf
vfwprintf
vprintf
vwprintf
wprintf
wscanf
10.2 POSIX 1003.1j
Reader/writer locks:
int rwlock_attr_init (rwlock_attr_t *attr); int rwlock_attr_destroy (rwlock_attr_t *attr); int rwlock_attr_getpshared (
const rwlock_attr_t *attr, int *pshared); int rwlock_attr_setpshared (
rwlock_attr_t *attr, int pshared); int rwlock_init (
rwlock_t *lock, const rwlock_attr_t *attr); int rwlock_destroy (rwlock_t *lock); int rwlock_rlock (rwlock_t *lock); int rwlock_timedrlock (rwlock_t *lock,
const struct timespec *timeout); int rwlock_tryrlock (rwlock_t *lock); int rwlock_wlock (rwlock_t *lock); int rwlock_timedwlock (rwlock_t *lock,
const struct timespec *timeout); int rwlock_trywlock (rwlock_t *lock); int rwlock_unlock (rwlock_t *lock);
Spinlocks:
int spin_init (spinlock_t *lock);
int spin_destroy (spinlock_t *lock);
int spin_lock (spinlock_t *lock);
int spin_trylock (spinlock_t *lock);
int spin_unlock (spinlock_t *lock);
int pthread_spin_init (pthread_spinlock_t *lock);
int pthread_spin_destroy (pthread_spinlock_t *lock);
int pthread_spin_lock (pthread_spinlock_t *lock);
int pthread_spin_trylock (pthread_spinlock_t *lock);
int pthread_spin_unlock (pthread_spinlock_t *lock);
Thread abort:
int pthread_abort (pthread_t thread);
The same POSIX working group that developed POSIX. lb and Pthreads has developed a new set of extensions for realtime and threaded programming. Most of the extensions relevant to threads (and to this book) are the result of proposals developed by the POSIX 1003.14 profile group, which specialized in "tuning" the existing POSIX standards for multiprocessor systems.
POSIX. lj adds some thread synchronization mechanisms that have been common in a wide range of multiprocessor and thread programming, but that had been omitted from the original Pthreads standard. Barriers and spinlocks are primarily useful for flne-grained parallelism, for example, in systems that automatically
generate parallel code from program loops. Read/write locks are useful in shared data algorithms where many threads are allowed to read simultaneously, but only one thread can be allowed to update data.
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