Re: race condition in libports

[Samuel Thibault]

Samuel Thibault, on sam. 06 janv. 2018 02:03:11 +0100, wrote:
> Brent W. Baccala, on ven. 05 janv. 2018 19:47:37 -0500, wrote:
> > Well, in that case, perhaps it should work by checking to see if the port 
> > is in
> > the hash, rather than by looking at how many weak references it's got. 
> > Something more like this:
> > 
> >   if ((refcounts_hard_references(&i->pi.refcounts) == 0)
> >       && (* i->id_hashloc == i))
> >     {
> >       /* Nobody got a send right in between, we can remove from the hash.  
> > */
> >       hurd_ihash_locp_remove (&idhash, i->id_hashloc);
> >       ports_port_deref_weak (&i->pi);
> >     }
> 
> You can't afford dereferencing id_hashloc like that: it could have
> gotten away in between.
> 
> Could you try the attached patch instead?

Actually that's what libdiskfs/node-cache.c does :)

Samuel