knlist_empty locking fix
John Baldwin
jhb at freebsd.org
Fri Jan 27 19:56:55 UTC 2012
On Friday, January 27, 2012 2:14:55 pm Doug Ambrisko wrote:
> John Baldwin writes:
> | On Friday, January 27, 2012 12:52:18 pm Kostik Belousov wrote:
> | > On Fri, Jan 27, 2012 at 09:42:58AM -0800, Doug Ambrisko wrote:
> | > > Andrew Boyer writes:
> | > > | On Jan 27, 2012, at 12:15 PM, Doug Ambrisko wrote:
> | > > |
> | > > | > John Baldwin writes:
> | > > | > | Agreed, I think the missing locking should just be added to the
aio
> | code.
> | > > | >
> | > > | > Okay so then just:
> | > > | >
> | > > | > Index: vfs_aio.c
> | > > | >
===================================================================
> | > > | > RCS file: /usr/local/cvsroot/freebsd/src/sys/kern/vfs_aio.c,v
> | > > | > retrieving revision 1.243.2.3.4.1
> | > > | > diff -u -p -r1.243.2.3.4.1 vfs_aio.c
> | > > | > --- vfs_aio.c 21 Dec 2010 17:09:25 -0000 1.243.2.3.4.1
> | > > | > +++ vfs_aio.c 27 Jan 2012 17:07:11 -0000
> | > > | > @@ -2509,9 +2509,12 @@ static void
> | > > | > filt_aiodetach(struct knote *kn)
> | > > | > {
> | > > | > struct aiocblist *aiocbe = kn->kn_ptr.p_aio;
> | > > | > + struct knlist *knl = &aiocbe->klist;
> | > > | >
> | > > | > - if (!knlist_empty(&aiocbe->klist))
> | > > | > - knlist_remove(&aiocbe->klist, kn, 0);
> | > > | > + knl->kl_lock(knl->kl_lockarg);
> | > > | > + if (!knlist_empty(knl))
> | > > | > + knlist_remove(knl, kn, 1);
> | > > | > + knl->kl_unlock(knl->kl_lockarg);
> | > > | > }
> | > > | >
> | > > | > /* kqueue filter function */
> | > > | >
> | > > | > I was trying to be consistant with knlist_remove but this is a
much
> | > > | > smaller change that can be merge to older branches.
> | > > |
> | > > | Does filt_liodetach() need the same treatment?
> | > >
> | > > Yes, I had that in the original. I updated that and optimized
> | > > the knl to just get the structure needed.
> | > >
> | > > Index: vfs_aio.c
> | > > ===================================================================
> | > > RCS file: /usr/local/cvsroot/freebsd/src/sys/kern/vfs_aio.c,v
> | > > retrieving revision 1.243.2.3.4.1
> | > > diff -u -p -r1.243.2.3.4.1 vfs_aio.c
> | > > --- vfs_aio.c 21 Dec 2010 17:09:25 -0000 1.243.2.3.4.1
> | > > +++ vfs_aio.c 27 Jan 2012 17:35:47 -0000
> | > > @@ -2508,10 +2508,12 @@ filt_aioattach(struct knote *kn)
> | > > static void
> | > > filt_aiodetach(struct knote *kn)
> | > > {
> | > > - struct aiocblist *aiocbe = kn->kn_ptr.p_aio;
> | > > + struct knlist *knl = &kn->kn_ptr.p_aio->klist;
> | > >
> | > > - if (!knlist_empty(&aiocbe->klist))
> | > > - knlist_remove(&aiocbe->klist, kn, 0);
> | > > + knl->kl_lock(knl->kl_lockarg);
> | > > + if (!knlist_empty(knl))
> | > > + knlist_remove(knl, kn, 1);
> | > > + knl->kl_unlock(knl->kl_lockarg);
> | > > }
> | > >
> | > > /* kqueue filter function */
> | > > @@ -2553,10 +2555,12 @@ filt_lioattach(struct knote *kn)
> | > > static void
> | > > filt_liodetach(struct knote *kn)
> | > > {
> | > > - struct aioliojob * lj = kn->kn_ptr.p_lio;
> | > > + struct knlist *knl = &kn->kn_ptr.p_lio->klist;
> | > It is easy to be style-compiant there and move initialization of knl
> | > after the blank line.
> | >
> | > Do you need two different functions now ? I think you can leave just
one.
> |
> | Hmm, I think p_lio != p_aio, so two functions are required.
>
> Correct, even thought they are together in a union, the structures are
> different so klist would have a different offset for each function.
>
> | I think the patch looks fine. The style fix to not assign 'knl' in its
> | declaration would be nice to fix as you suggested, but that's minor.
>
> Here is the updated version that seems to work fine.
Looks good to me.
--
John Baldwin
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