Re: lockmgr_sleep() (was Re: ssleep() (was Re: mention msleep() in porting_drivers.txt))

["Simon 'corecode' Schubert" <corecode@xxxxxxxxxxxx>]

Aggelos Economopoulos wrote:
> On Wednesday 16 January 2008, Simon 'corecode' Schubert wrote:
> > Aggelos Economopoulos wrote:
> > > So, about adding a lockmgr_sleep(): I think it would be useful; open-coding
> > > the whole thing makes it easy to slip in hard to notice bugs. But what should
> > > the prototype be? If we follow the freebsd semantics, the lock should be re-
> > > acquired on return. This means that we need to do a lockstatus() (which implies
> > > a spin_lock_wr()) to get information that the caller probably has available or
> > Why?  When we release the lock in lock_sleep, we will obtain the status 
> > anyways, right?
> Assuming you mean lockmgr_sleep() here, no. lockmgr(LK_RELEASE) only returns
> 0. OTOH nobody in the tree actually checks for that, so we could change
> lockmgr to return the lock status in that case. This seems to solve the
> problem nicely. Any objections to that?

lockmgr_sleep (or lock_sleep?) knows the internals of a lockmgr lock and 
thus can optimize the access.

> > > The down side of course is having to change a couple of dozen call sites. But
> > > as long as we're breaking people's patches with the name change, we might as
> > > well fix the interface, assuming everyone agrees that's an improvement.
> > No problem.  We could keep msleep() around for some time.
> Maybe for a little bit (and with a big warning to prevent people from using
> it; this is a good chance to bring in __attribute__(deprecated)) in order to
> avoid breakage for out of tree code, but if we add spin_sleep(), msleep()
> has to go. We don't want to end up like freebsd (which has mtx_sleep() AND
> msleep()), right? ;)

You mean msleep() has to go after a deprecation period, right?  (period 
being one release cycle = 6 months)

cheers
  simon

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