HP-UX Reference (11i v1 05/09) - 3 Library Functions N-Z (vol 7)

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pthread_mutexattr_getpshared(3T) pthread_mutexattr_getpshared(3T)

(Pthread Library)

error. This type of mutex is useful for debugging.

PTHREAD_MUTEX_RECURSIVE

Deadlock cannot occur with this type of mutex. An owner ﬁeld is maintained. A thread attempt-

ing to relock this mutex shall successfully lock the mutex. Multiple locks of this mutex shall

require the same number of unlocks to release the mutex before another thread can lock the

mutex. A thread attempting to unlock a mutex locked by a different thread shall return with an

error. A thread attempting to unlock an unlocked mutex shall return with an error.

PTHREAD_MUTEX_DEFAULT

Attempting to recursively lock a mutex of this type results in undeﬁned behavior. Attempting to

unlock a mutex locked by a different thread results in undeﬁned behavior. Attempting to unlock

an unlocked mutex results in undeﬁned behavior. An implementation shall be allowed to map

this mutex to one of the other mutex types.

The default value of the type attribute is

PTHREAD_MUTEX_DEAFULT

pthread_mutexattr_settype()

is used to set the type attribute in attr. The new value of the type

attribute of attr is set to the value speciﬁed in the type parameter.

pthread_mutexattr_gettype()

retrieves the value of the type attribute from attr. The value of

the type attribute of attr is returned in the type parameter.

Never use a

PTHREAD_MUTEX_RECURSIVE

mutex with condition variables because the implicit unlock

performed for a

pthread_cond_wait()

or pthread_cond_timedwait() may not actually

release the mutex if it had been locked multiple times. If this situation happens, no other thread can

satisfy the condition of the predicate.

RETURN VALUE

Upon successful completion,

pthread_mutexattr_getpshared()

pthread_mutexattr_setpshared()

, pthread_mutexattr_gettype()

, and

pthread_mutexattr_settype()

return zero. Otherwise, an error number is returned to indicate

the error (the

errno variable is not set).

ERRORS

If any of the following occur, the pthread_mutexattr_getpshared()

and

pthread_mutexattr_setpshared()

functions return the corresponding error number:

[ENOSYS]

_POSIX_THREAD_PROCESS_SHARED

is not deﬁned and these functions are not

supported.

For each of the following conditions, if the condition is detected, the

pthread_mutexattr_getpshared()

, pthread_mutexattr_setpshared()

pthread_mutexattr_gettype()

, and pthread_mutexattr_settype()

functions return the

corresponding error number:

[EINVAL] attr is not a valid mutex attributes object.

[EINVAL] The value speciﬁed by pshared or type is not a legal value. [EINVAL] The value

pshared or type points to an illegal address.

WARNINGS

If a mutex is created with the process-shared attribute deﬁned as

PTHREAD_PROCESS_SHARED

, the

cooperating processes should have access to the memory in which the mutex is allocated.

AUTHOR

pthread_mutexattr_setpshared() and pthread_mutexattr_getpshared()

were derived

from the IEEE POSIX P1003.1c standard.

pthread_mutexattr_settype(), and pthread_mutexattr_gettype()

were developed by

X/Open.