svn commit: r297394 - head/share/man/man9
Bryan Drewery
bdrewery at FreeBSD.org
Tue Mar 29 16:07:52 UTC 2016
Author: bdrewery
Date: Tue Mar 29 16:07:51 2016
New Revision: 297394
URL: https://svnweb.freebsd.org/changeset/base/297394
Log:
Reword descriptions of asserting locks held without WITNESS.
This corrects an error in r296947 in that it is not possible to assert
which thread holds a shared (or read) lock, but it is possible to assert
that one is held. Just not very useful.
MFC after: 1 week
Submitted by: wblock, jhb
Reviewed by: kib (earlier version), jhb, wblock
Sponsored by: EMC / Isilon Storage Division
Differential Revision: https://reviews.freebsd.org/D5659
Modified:
head/share/man/man9/rwlock.9
head/share/man/man9/sx.9
Modified: head/share/man/man9/rwlock.9
==============================================================================
--- head/share/man/man9/rwlock.9 Tue Mar 29 15:26:53 2016 (r297393)
+++ head/share/man/man9/rwlock.9 Tue Mar 29 16:07:51 2016 (r297394)
@@ -24,7 +24,7 @@
.\"
.\" $FreeBSD$
.\"
-.Dd December 13, 2014
+.Dd March 28, 2016
.Dt RWLOCK 9
.Os
.Sh NAME
@@ -313,18 +313,19 @@ facility was written by
This manual page was written by
.An "Gleb Smirnoff" .
.Sh BUGS
-If
+A kernel without
.Dv WITNESS
-is not included in the kernel,
-then it is impossible to assert that the current thread does or does not
-hold a read lock.
-In the
-.Pf non- Dv WITNESS
-case, the
+cannot assert whether the current thread does or does not hold a read lock.
.Dv RA_LOCKED
and
.Dv RA_RLOCKED
-assertions merely check that some thread holds a read lock.
+can only assert that
+.Em any
+thread holds a read lock.
+They cannot ensure that the current thread holds a read lock.
+Further,
+.Dv RA_UNLOCKED
+can only assert that the current thread does not hold a write lock.
.Pp
Reader/writer is a bit of an awkward name.
An
Modified: head/share/man/man9/sx.9
==============================================================================
--- head/share/man/man9/sx.9 Tue Mar 29 15:26:53 2016 (r297393)
+++ head/share/man/man9/sx.9 Tue Mar 29 16:07:51 2016 (r297394)
@@ -26,7 +26,7 @@
.\"
.\" $FreeBSD$
.\"
-.Dd March 16, 2016
+.Dd March 28, 2016
.Dt SX 9
.Os
.Sh NAME
@@ -320,11 +320,16 @@ end up sleeping while holding a mutex, w
.Xr rwlock 9 ,
.Xr sema 9
.Sh BUGS
-In the
-.No non- Ns Dv WITNESS
-case, the
+A kernel without
+.Dv WITNESS
+cannot assert whether the current thread does or does not hold a shared lock.
.Dv SA_LOCKED
and
.Dv SA_SLOCKED
-assertions merely check that some thread holds a shared lock.
-They do not ensure that the current thread holds a shared lock.
+can only assert that
+.Em any
+thread holds a shared lock.
+They cannot ensure that the current thread holds a shared lock.
+Further,
+.Dv SA_UNLOCKED
+can only assert that the current thread does not hold an exclusive lock.
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