2018-11-26 16:49:40

by Andrea Parri

Subject: [PATCH] afs: Add missing memory barriers in afs_manage_cell()

As the comments for wake_up_bit() and waitqueue_active() point out,
the barriers are needed to order the clearing of the _FL_NOT_READY
bit and the waitqueue_active() load; match the implicit barrier in
prepare_to_wait().

Signed-off-by: Andrea Parri <[email protected]>
---
fs/afs/cell.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/fs/afs/cell.c b/fs/afs/cell.c
index cf445dbd5f2e0..a9488abe56029 100644
--- a/fs/afs/cell.c
+++ b/fs/afs/cell.c
@@ -637,6 +637,7 @@ static void afs_manage_cell(struct work_struct *work)
cell->state = AFS_CELL_ACTIVE;
smp_wmb();
clear_bit(AFS_CELL_FL_NOT_READY, &cell->flags);
+ smp_mb__after_atomic(); /* see comment for wake_up_bit() */
wake_up_bit(&cell->flags, AFS_CELL_FL_NOT_READY);
goto again;

@@ -678,6 +679,7 @@ static void afs_manage_cell(struct work_struct *work)
cell->state = AFS_CELL_ACTIVE;
smp_wmb();
clear_bit(AFS_CELL_FL_NOT_READY, &cell->flags);
+ smp_mb__after_atomic(); /* see comment for wake_up_bit() */
wake_up_bit(&cell->flags, AFS_CELL_FL_NOT_READY);
_leave(" [deact->act]");
return;
--
2.17.1

2019-01-17 15:34:48

by Andrea Parri

Subject: Re: [PATCH] afs: Add missing memory barriers in afs_manage_cell()

On Mon, Nov 26, 2018 at 05:44:12PM +0100, Andrea Parri wrote:
> As the comments for wake_up_bit() and waitqueue_active() point out,
> the barriers are needed to order the clearing of the _FL_NOT_READY
> bit and the waitqueue_active() load; match the implicit barrier in
> prepare_to_wait().
>
> Signed-off-by: Andrea Parri <[email protected]>

Hi David, do you have any feedback on this?

Andrea


> ---
> fs/afs/cell.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/fs/afs/cell.c b/fs/afs/cell.c
> index cf445dbd5f2e0..a9488abe56029 100644
> --- a/fs/afs/cell.c
> +++ b/fs/afs/cell.c
> @@ -637,6 +637,7 @@ static void afs_manage_cell(struct work_struct *work)
> cell->state = AFS_CELL_ACTIVE;
> smp_wmb();
> clear_bit(AFS_CELL_FL_NOT_READY, &cell->flags);
> + smp_mb__after_atomic(); /* see comment for wake_up_bit() */
> wake_up_bit(&cell->flags, AFS_CELL_FL_NOT_READY);
> goto again;
>
> @@ -678,6 +679,7 @@ static void afs_manage_cell(struct work_struct *work)
> cell->state = AFS_CELL_ACTIVE;
> smp_wmb();
> clear_bit(AFS_CELL_FL_NOT_READY, &cell->flags);
> + smp_mb__after_atomic(); /* see comment for wake_up_bit() */
> wake_up_bit(&cell->flags, AFS_CELL_FL_NOT_READY);
> _leave(" [deact->act]");
> return;
> --
> 2.17.1
>

2019-01-31 18:30:13

by Andrea Parri

Subject: Re: [PATCH] afs: Add missing memory barriers in afs_manage_cell()

On Thu, Jan 17, 2019 at 04:31:32PM +0100, Andrea Parri wrote:
> On Mon, Nov 26, 2018 at 05:44:12PM +0100, Andrea Parri wrote:
> > As the comments for wake_up_bit() and waitqueue_active() point out,
> > the barriers are needed to order the clearing of the _FL_NOT_READY
> > bit and the waitqueue_active() load; match the implicit barrier in
> > prepare_to_wait().
> >
> > Signed-off-by: Andrea Parri <[email protected]>
>
> Hi David, do you have any feedback on this?

ping


>
> Andrea
>
>
> > ---
> > fs/afs/cell.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/fs/afs/cell.c b/fs/afs/cell.c
> > index cf445dbd5f2e0..a9488abe56029 100644
> > --- a/fs/afs/cell.c
> > +++ b/fs/afs/cell.c
> > @@ -637,6 +637,7 @@ static void afs_manage_cell(struct work_struct *work)
> > cell->state = AFS_CELL_ACTIVE;
> > smp_wmb();
> > clear_bit(AFS_CELL_FL_NOT_READY, &cell->flags);
> > + smp_mb__after_atomic(); /* see comment for wake_up_bit() */
> > wake_up_bit(&cell->flags, AFS_CELL_FL_NOT_READY);
> > goto again;
> >
> > @@ -678,6 +679,7 @@ static void afs_manage_cell(struct work_struct *work)
> > cell->state = AFS_CELL_ACTIVE;
> > smp_wmb();
> > clear_bit(AFS_CELL_FL_NOT_READY, &cell->flags);
> > + smp_mb__after_atomic(); /* see comment for wake_up_bit() */
> > wake_up_bit(&cell->flags, AFS_CELL_FL_NOT_READY);
> > _leave(" [deact->act]");
> > return;
> > --
> > 2.17.1
> >