cvs commit: src/share/man/man9 lock.9

[John Baldwin]

On Thursday 24 August 2006 16:16, Julian Elischer wrote:
> Konstantin Belousov wrote:
> 
> >kib         2006-08-24 10:16:01 UTC
> >
> >  FreeBSD src repository
> >
> >  Modified files:        (Branch: RELENG_6)
> >    share/man/man9       lock.9 
> >  Log:
> >  MFC rev.1.14:
> >  Note that LK_UPGRADE may drop the shared lock before taking the
> >  exclusive one.
> >  
> >  
> >
> excuse my ignorance but I though that the whole aim of an upgrade was to 
> make sure that
> you did NOT drop it before getting the exclusive lock..( or it fails and 
> you back out and retry)

This is why sx and rw locks only have a try_upgrade and not a blocking
upgrade.  The calling code can then do a sunlock and blocking xlock
and make sure they redo any needed checks, etc.

> >  Reviewed and edited by: tegge
> >  Approved by:    pjd (mentor)
> >  
> >  Revision  Changes    Path
> >  1.12.2.2  +2 -0      src/share/man/man9/lock.9
> >  
> >
> 

-- 
John Baldwin