svn commit: r284646 - head/share/man/man9

[Konstantin Belousov]

Author: kib
Date: Sat Jun 20 17:18:46 2015
New Revision: 284646
URL: https://svnweb.freebsd.org/changeset/base/284646

Log:
  The barriers, provided by _acq and _rel atomics, are acquire and
  release barriers, not read and write barriers.  They fence all memory
  accesses from the respective side, not limited by the kind of
  operation.
  
  Reviewed by:	jhb
  Sponsored by:	The FreeBSD Foundation
  MFC after:	1 week

Modified:
  head/share/man/man9/atomic.9

Modified: head/share/man/man9/atomic.9
==============================================================================
--- head/share/man/man9/atomic.9	Sat Jun 20 15:55:53 2015	(r284645)
+++ head/share/man/man9/atomic.9	Sat Jun 20 17:18:46 2015	(r284646)
@@ -23,7 +23,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd August 20, 2013
+.Dd June 20, 2015
 .Dt ATOMIC 9
 .Os
 .Sh NAME
@@ -123,7 +123,9 @@ The first form just performs the operati
 The second form uses a read memory barrier, and the third variant uses a write
 memory barrier.
 .Pp
-The second variant of each operation includes a read memory barrier.
+The second variant of each operation includes an
+.Em acquire
+memory barrier.
 This barrier ensures that the effects of this operation are completed before the
 effects of any later data accesses.
 As a result, the operation is said to have acquire semantics as it acquires a
@@ -137,7 +139,9 @@ For example, to subtract two integers en
 happen after the subtraction is performed, use
 .Fn atomic_subtract_acq_int .
 .Pp
-The third variant of each operation includes a write memory barrier.
+The third variant of each operation includes a
+.Em release
+memory barrier.
 This ensures that all effects of all previous data accesses are completed
 before this operation takes place.
 As a result, the operation is said to have release semantics as it releases