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Update rwlock(9) manpage adding missing bits about the rw_init_flags()

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function, its options and explaining that recursion for writers can be
selectively enabled.

Reported by: rwatson, Skip Ford <skip at menantico dot com>
This commit is contained in:
Attilio Rao 2007-11-25 01:53:58 +00:00
parent 2b19cb1b87
commit 6442838d08
1 changed files with 33 additions and 2 deletions
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35
share/man/man9/rwlock.9
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@ -30,6 +30,7 @@
.Sh NAME
.Nm rwlock ,
.Nm rw_init ,
.Nm rw_init_flags,
.Nm rw_destroy ,
.Nm rw_rlock ,
.Nm rw_wlock ,
@ -50,6 +51,8 @@
.Ft void
.Fn rw_init "struct rwlock *rw" "const char *name"
.Ft void
.Fn rw_init_flags "struct rwlock *rw" "const char *name" "int opts"
.Ft void
.Fn rw_destroy "struct rwlock *rw"
.Ft void
.Fn rw_rlock "struct rwlock *rw"
@ -108,7 +111,7 @@ are anonymous.
Another important property is that shared holders of
.Nm
can recurse,
but exclusive locks are not allowed to recurse.
and exclusive locks can be made recursive selectively.
.Ss Macros and Functions
.Bl -tag -width indent
.It Fn rw_init "struct rwlock *rw" "const char *name"
@ -119,6 +122,30 @@ as reader/writer lock, described by name
The description is used solely for debugging purposes.
This function must be called before any other operations
on the lock.
.It Fn rw_init_flags "struct rwlock *rw" "const char *name" "int opts"
Initialize the rw lock just like
.Fn rw_init
function, but specifing a set of optional flags to alter the
behaviour of
.Fa rw ,
through the
.Fa opts
argument. It contains one or more of the following flags:
.Bl -tag -width ".Dv RW_NOPROFILE"
.It Dv RW_DUPOK
Witness should not log messages about duplicate locks being acquired.
.It Dv RW_NOPROFILE
Do not profile this lock.
.It Dv RW_NOWITNESS
Instruct
.Xr witness 4
to ignore this lock.
.It Dv RW_QUIET
Do not log any operations for this lock via
.Xr ktr 4 .
.It Dv RW_RECURSE
Allow threads to recursively acquire exclusive locks for
.Fa rw .
.It Fn rw_rlock "struct rwlock *rw"
Lock
.Fa rw
@ -139,7 +166,11 @@ as a writer.
If there are any shared owners of the lock, the current thread blocks.
The
.Fn rw_wlock
function cannot be called recursively.
function can be called recursively only if
.Fa rw
has been initialized with the
.Dv RW_RECURSE
option enabled.
.It Fn rw_runlock "struct rwlock *rw"
This function releases a shared lock previously acquired by
.Fn rw_rlock .