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12 .TH PTHREAD_MUTEXATTR_GETTYPE 3C "Mar 23, 2005"
14 pthread_mutexattr_gettype, pthread_mutexattr_settype \- get or set mutex type
18 cc -mt [ \fIflag\fR... ] \fIfile\fR... -lpthread [ \fIlibrary\fR... ]
21 \fBint\fR \fBpthread_mutexattr_gettype\fR(\fBpthread_mutexattr_t *restrict\fR \fIattr\fR,
22 \fBint *restrict\fR \fItype\fR);
27 \fBint\fR \fBpthread_mutexattr_settype\fR(\fBpthread_mutexattr_t *\fR\fIattr\fR, \fBint\fR \fItype\fR);
33 The \fBpthread_mutexattr_gettype()\fR and \fBpthread_mutexattr_settype()\fR
34 functions respectively get and set the mutex \fItype\fR attribute. This
35 attribute is set in the \fItype\fR parameter to these functions. The default
36 value of the \fItype\fR attribute is \fBPTHREAD_MUTEX_DEFAULT\fR.
39 The type of mutex is contained in the \fItype\fR attribute of the mutex
40 attributes. Valid mutex types include:
44 \fB\fBPTHREAD_MUTEX_NORMAL\fR\fR
47 This type of mutex does not detect deadlock. A thread attempting to relock this
48 mutex without first unlocking it will deadlock. Attempting to unlock a mutex
49 locked by a different thread results in undefined behavior. Attempting to
50 unlock an unlocked mutex results in undefined behavior.
56 \fB\fBPTHREAD_MUTEX_ERRORCHECK\fR\fR
59 This type of mutex provides error checking. A thread attempting to relock this
60 mutex without first unlocking it will return with an error. A thread attempting
61 to unlock a mutex that another thread has locked will return with an error. A
62 thread attempting to unlock an unlocked mutex will return with an error.
68 \fB\fBPTHREAD_MUTEX_RECURSIVE\fR\fR
71 A thread attempting to relock this mutex without first unlocking it will
72 succeed in locking the mutex. The relocking deadlock that can occur with
73 mutexes of type \fBPTHREAD_MUTEX_NORMAL\fR cannot occur with this type of
74 mutex. Multiple locks of this mutex require the same number of unlocks to
75 release the mutex before another thread can acquire the mutex. A thread
76 attempting to unlock a mutex that another thread has locked will return with an
77 error. A thread attempting to unlock an unlocked mutex will return with an
78 error. This type of mutex is only supported for mutexes whose process shared
79 attribute is \fBPTHREAD_PROCESS_PRIVATE\fR.
85 \fB\fBPTHREAD_MUTEX_DEFAULT\fR\fR
88 Attempting to recursively lock a mutex of this type results in undefined
89 behavior. Attempting to unlock a mutex of this type that was not locked by the
90 calling thread results in undefined behavior. Attempting to unlock a mutex of
91 this type that is not locked results in undefined behavior. An implementation
92 is allowed to map this mutex to one of the other mutex types.
98 Upon successful completion, the \fBpthread_mutexattr_settype()\fR function
99 returns \fB0\fR. Otherwise, an error number is returned to indicate the error.
102 Upon successful completion, the \fBpthread_mutexattr_gettype()\fR function
103 returns \fB0\fR and stores the value of the \fItype\fR attribute of \fIattr\fR
104 in the object referenced by the \fItype\fR parameter. Otherwise an error number
105 is returned to indicate the error.
109 The \fBpthread_mutexattr_gettype()\fR and \fBpthread_mutexattr_settype()\fR
110 functions will fail if:
117 The value \fBtype\fR is invalid.
122 The \fBpthread_mutexattr_gettype()\fR and \fBpthread_mutexattr_settype()\fR
123 functions may fail if:
130 The value specified by \fIattr\fR is invalid.
136 See \fBattributes\fR(5) for descriptions of the following attributes:
144 ATTRIBUTE TYPE ATTRIBUTE VALUE
146 Interface Stability Standard
154 \fBpthread_cond_timedwait\fR(3C), \fBpthread_cond_wait\fR(3C),
155 \fBattributes\fR(5), \fBstandards\fR(5)
159 Application should not use a \fBPTHREAD_MUTEX_RECURSIVE\fR mutex with condition
160 variables because the implicit unlock performed for \fBpthread_cond_wait()\fR
161 or \fBpthread_cond_timedwait()\fR will not actually release the mutex (if it
162 had been locked multiple times). If this occurs, no other thread can satisfy
163 the condition of the predicate.