Re: CVS commit: src/sys/uvm

[Mindaugas Rasiukevicius <rmind%netbsd.org@localhost>]

yamt%mwd.biglobe.ne.jp@localhost (YAMAMOTO Takashi) wrote:
> > 
> > Here is the updated patch after your changes:
> > 
> > http://www.netbsd.org/~rmind/uvm_anon_freelst2.diff
> > 
> > As you noted, uvm_anfree() can temporarily release the amap lock - that
> > can happen in amap_copy().  Patch closes the race by moving uvm_anfree
> > () further, and changes the semantics of the function, now called
> > uvm_anon_freelst(), to return with amap lock released (plus free anons
> > without lock held).
> 
> the temporary release of the amap lock is only for O->A loan
> which you disabled, isn't it?

Right, uvm_anon_locklaonpg() dance can happen only in O->A case.  However,
having uvm_anfree() able to release the lock by its interface definition
is potentially defective.  It is the main motivation why I want to slightly
rework the code into uvm_anon_freelst() which would always drop the lock
and move freeing of anons to the end point.  Cleaner, less error prone.

-- 
Mindaugas