Date: Fri, 27 Jan 2012 11:14:55 -0800 (PST) From: Doug Ambrisko <ambrisko@ambrisko.com> To: John Baldwin <jhb@freebsd.org> Cc: Kostik Belousov <kostikbel@gmail.com>, freebsd-current@freebsd.org, Andrew Boyer <aboyer@averesystems.com> Subject: Re: knlist_empty locking fix Message-ID: <201201271914.q0RJEt1C005544@ambrisko.com> In-Reply-To: <201201271302.59011.jhb@freebsd.org>
next in thread | previous in thread | raw e-mail | index | archive | help
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.
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 18:22:10 -0000
@@ -2508,10 +2508,13 @@ filt_aioattach(struct knote *kn)
static void
filt_aiodetach(struct knote *kn)
{
- struct aiocblist *aiocbe = kn->kn_ptr.p_aio;
+ struct knlist *knl;
- if (!knlist_empty(&aiocbe->klist))
- knlist_remove(&aiocbe->klist, kn, 0);
+ knl = &kn->kn_ptr.p_aio->klist;
+ 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 +2556,13 @@ filt_lioattach(struct knote *kn)
static void
filt_liodetach(struct knote *kn)
{
- struct aioliojob * lj = kn->kn_ptr.p_lio;
+ struct knlist *knl;
- if (!knlist_empty(&lj->klist))
- knlist_remove(&lj->klist, kn, 0);
+ knl = &kn->kn_ptr.p_lio->klist;
+ knl->kl_lock(knl->kl_lockarg);
+ if (!knlist_empty(knl))
+ knlist_remove(knl, kn, 1);
+ knl->kl_unlock(knl->kl_lockarg);
}
/* kqueue filter function */
Thanks,
Doug A.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201201271914.q0RJEt1C005544>