This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

       It is advised that an application should not use a PTHREAD_MUTEX_RECURSIVE mutex with condition variables
       because the implicit unlock performed for  a  pthread_cond_timedwait()  or  pthread_cond_wait()  may  not
       actually  release  the mutex (if it had been locked multiple times). If this happens, no other thread can
       satisfy the condition of the predicate.

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for  Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical  and  Electronics
       Engineers, Inc and The Open Group.  In the event of any discrepancy between this version and the original
       IEEE  and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document.
       The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are most likely to have  been  introduced
       during   the   conversion  of  the  source  files  to  man  page  format.  To  report  such  errors,  see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                     PTHREAD_MUTEXATTR_GETTYPE(3POSIX)

       The  pthread_mutexattr_gettype()  and  pthread_mutexattr_settype() functions, respectively, shall get and
       set the mutex type attribute. This attribute is set in the type parameter to these functions. The default
       value of the type attribute is PTHREAD_MUTEX_DEFAULT.

       The type of mutex is contained in the type attribute of the mutex attributes. Valid mutex types include:

              PTHREAD_MUTEX_NORMAL PTHREAD_MUTEX_ERRORCHECK PTHREAD_MUTEX_RECURSIVE PTHREAD_MUTEX_DEFAULT

       The mutex type affects the behavior of calls which lock and unlock the  mutex.  See  pthread_mutex_lock()
       for details. An implementation may map PTHREAD_MUTEX_DEFAULT to one of the other mutex types.

       The  behavior  is undefined if the value specified by the attr argument to pthread_mutexattr_gettype() or
       pthread_mutexattr_settype() does not refer to an initialized mutex attributes object.

       The pthread_mutexattr_settype() function shall fail if:

       EINVAL The value type is invalid.

       These functions shall not return an error code of [EINTR].

       Thefollowingsectionsareinformative.

       None.

       None.

       pthread_mutexattr_gettype, pthread_mutexattr_settype — get and set the mutex type attribute

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of this interface
       may differ (consult the corresponding Linux manual page for details of Linux behavior), or the  interface
       may not be implemented on Linux.

       If an implementation detects that the value specified by the attr argument to pthread_mutexattr_gettype()
       or pthread_mutexattr_settype()  does  not  refer  to  an  initialized  mutex  attributes  object,  it  is
       recommended that the function should fail and report an [EINVAL] error.

       Upon successful completion, the pthread_mutexattr_gettype() function shall  return  zero  and  store  the
       value of the type attribute of attr into the object referenced by the type parameter. Otherwise, an error
       shall be returned to indicate the error.

       If  successful,  the  pthread_mutexattr_settype()  function shall return zero; otherwise, an error number
       shall be returned to indicate the error.

pthread_cond_timedwait(), pthread_mutex_lock()

       The Base Definitions volume of POSIX.1‐2017, <pthread.h>

       #include <pthread.h>

       int pthread_mutexattr_gettype(const pthread_mutexattr_t *restrict attr,
           int *restrict type);
       int pthread_mutexattr_settype(pthread_mutexattr_t *attr, int type);