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Document rw_try_upgrade() and rw_downgrade().

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This commit is contained in:
John Baldwin 2006-04-19 21:09:17 +00:00
parent fea3efe5bf
commit 96cb5f9912
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=157883
1 changed files with 23 additions and 0 deletions
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23
share/man/man9/rwlock.9
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@ -54,6 +54,10 @@
.Ft void
.Fn rw_wunlock "struct rwlock *rw"
.Ft int
.Fn rw_try_upgrade "struct rwlock *rw"
.Ft void
.Fn rw_downgrade "struct rwlock *rw"
.Ft int
.Fn rw_initialized "struct rwlock *rw"
.Ft void
.Fn rw_destroy "struct rwlock *rw"
@ -134,6 +138,25 @@ This function releases a shared lock previously acquired by
.It Fn rw_wunlock "struct rwlock *rw"
This function releases an exclusive lock previously acquired by
.Fn rw_wlock .
.It Fn rw_try_upgrade "struct rwlock *rw"
Attempt to upgrade a single shared lock to an exclusive lock.
The current thread must hold a shared lock of
.Fa rw .
This will only succeed if the current thread holds the only shared lock on
.Fa rw ,
and it only holds a single shared lock.
If the attempt succeeds
.Fn rw_try_upgrade
will return a non-zero value,
and the current thread will hold an exclusive lock.
If the attempt fails
.Fn rw_try_upgrade
will return zero,
and the current thread will still hold a shared lock.
.It Fn rw_downgrade "struct rwlock *rw"
Convert an exclusive lock into a single shared lock.
The current thread must hold an exclusive lock of
.Fa rw .
.It Fn rw_initialized "struct rwlock *rw"
This function returns non-zero if
.Fa rw