knlist_empty locking fix

[Kostik Belousov]

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.

Otherwise looks fine.
>  
> -	if (!knlist_empty(&lj->klist))
> -		knlist_remove(&lj->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 */
> 
> Thanks,
> 
> Doug A.
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