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+.\"
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+.\" The contents of this file are subject to the terms of the
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+.\" Portions Copyright (c) 1995 IEEE  All Rights Reserved
+.\" Copyright (c) 1998 Sun Microsystems, Inc.  All Rights Reserved.
+.\" Copyright (c) 2001, The IEEE and The Open Group.  All Rights Reserved.
+.\"
+.TH CONDITION 7 "May 16, 2020"
+.SH NAME
+condition \- concepts related to condition variables
+.SH DESCRIPTION
+Occasionally, a thread running within a mutex needs to wait for an event,  in
+which case it blocks or sleeps. When a thread is waiting for another thread to
+communicate its disposition, it uses a condition variable in conjunction with a
+mutex. Although a mutex is exclusive and the code it protects is sharable (at
+certain moments), condition variables enable the synchronization of differing
+events that share a mutex, but not necessarily data. Several condition
+variables may be used by threads to signal each other  when a task is complete,
+which then allows the next waiting thread to take  ownership of the mutex.
+.sp
+.LP
+A condition variable enables threads to atomically block and test the condition
+under the protection of a  mutual exclusion lock (mutex) until the condition is
+satisfied. If the condition is false, a thread blocks on a condition variable
+and atomically releases the mutex that is waiting for the condition to change.
+If another thread changes the condition, it may wake up waiting threads by
+signaling the associated condition variable. The waiting threads, upon
+awakening, reacquire the mutex and re-evaluate the condition.
+.SS "Initialize"
+Condition variables and mutexes should be global. Condition variables that are
+allocated in writable memory can synchronize threads among processes if they
+are shared by the cooperating processes (see \fBmmap\fR(2)) and are initialized
+for this purpose.
+.sp
+.LP
+The scope of a condition variable is either intra-process or inter-process.
+This is dependent upon whether the argument is passed implicitly or explicitly
+to the initialization  of that condition variable. A condition variable does
+not need to be explicitly initialized. A condition variable is initialized with
+all zeros, by default, and its scope is set  to within the calling process. For
+inter-process synchronization, a condition variable must be initialized once,
+and only once, before use.
+.sp
+.LP
+A condition variable must not be simultaneously initialized by multiple threads
+or re-initialized while in use by other threads.
+.sp
+.LP
+Condition variables attributes may be set to the default or customized at
+initialization.  POSIX threads even allow the default values to be customized.
+Establishing these attributes varies depending upon whether POSIX or Solaris
+threads are used. Similar to the distinctions between POSIX and Solaris thread
+creation, POSIX condition variables implement the default, intra-process,
+unless an attribute object is modified for inter-process prior to the
+initialization of the condition variable. Solaris condition variables also
+implement as the default,  intra-process; however, they set this attribute
+according to the argument, \fItype\fR, passed to their initialization function.
+.SS "Condition Wait"
+The condition wait interface allows a thread to wait for a condition and
+atomically release the associated mutex that it needs to hold to check the
+condition. The thread waits for another thread to make the condition true and
+that thread's resulting call to signal and wakeup the waiting thread.
+.SS "Condition Signaling"
+A condition signal allows a thread to unblock the next thread waiting on the
+condition variable, whereas, a condition broadcast allows a thread to unblock
+all threads waiting on the  condition variable.
+.SS "Destroy"
+The condition destroy functions destroy any state, but not the space,
+associated with the condition variable.
+.SH ATTRIBUTES
+See \fBattributes\fR(7) for descriptions of the following attributes:
+.sp
+
+.sp
+.TS
+box;
+c | c
+l | l .
+ATTRIBUTE TYPE	ATTRIBUTE VALUE
+_
+MT-Level	MT-Safe
+.TE
+
+.SH SEE ALSO
+.BR fork (2),
+.BR mmap (2),
+.BR setitimer (2),
+.BR shmop (2),
+.BR cond_broadcast (3C),
+.BR cond_destroy (3C),
+.BR cond_init (3C),
+.BR cond_signal (3C),
+.BR cond_timedwait (3C),
+.BR cond_wait (3C),
+.BR pthread_cond_broadcast (3C),
+.BR pthread_cond_destroy (3C),
+.BR pthread_cond_init (3C),
+.BR pthread_cond_signal (3C),
+.BR pthread_cond_timedwait (3C),
+.BR pthread_cond_wait (3C),
+.BR pthread_condattr_init (3C),
+.BR signal (3C),
+.BR attributes (7),
+.BR mutex (7),
+.BR standards (7)
+.SH NOTES
+If more than one thread is blocked on a condition variable, the order in which
+threads are unblocked is determined by the scheduling policy.
+.sp
+.LP
+\fBUSYNC_THREAD\fR does not support multiple mappings to the same logical
+synch object. If you need to \fBmmap()\fR a synch object to different locations
+within the same address space, then the synch object should be initialized as a
+shared object \fBUSYNC_PROCESS\fR for Solaris, and
+\fBPTHREAD_PROCESS_PRIVATE\fR for POSIX.