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Document LK_TRYUPGRADE.

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Sponsored by:	The FreeBSD Foundation
MFC after:	3 days
Approved by:	re (marius)
This commit is contained in:
Konstantin Belousov 2013-10-06 15:59:06 +00:00
parent ac64499012
commit 5dc5cbb274
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=256089
1 changed files with 11 additions and 3 deletions
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14
share/man/man9/lock.9
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@ -26,7 +26,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd November 16, 2011
.Dd October 6, 2013
.Dt LOCK 9
.Os
.Sh NAME
@ -164,11 +164,17 @@ If an exclusive lock has been recursed, the system will
.Xr panic 9 .
.It Dv LK_UPGRADE
Upgrade a shared lock to an exclusive lock.
If this call fails, the shared lock is lost.
If this call fails, the shared lock is lost, even if the
.Dv LK_NOWAIT
flag is specified.
During the upgrade, the shared lock could
be temporarily dropped.
Attempts to upgrade an exclusive lock will cause a
.Xr panic 9 .
.It Dv LK_TRYUPGRADE
Try to upgrade a shared lock to an exclusive lock.
The failure to upgrade does not result in the dropping
of the shared lock ownership.
.It Dv LK_RELEASE
Release the lock.
Releasing a lock that is not held can cause a
@ -333,7 +339,9 @@ fail if:
was requested and another thread had already requested a lock upgrade.
.It Bq Er EBUSY
.Dv LK_NOWAIT
was set, and a sleep would have been required.
was set, and a sleep would have been required, or
.Dv LK_TRYUPGRADE
operation was not able to upgrade the lock.
.It Bq Er ENOLCK
.Dv LK_SLEEPFAIL
was set and