Re: [PATCH] dma-buf: fix locking in sync_print_obj()

[Chris Wilson <chris@chris-wilson.co.uk>]

Quoting Dan Carpenter (2020-01-24 10:31:23)
> On Fri, Jan 24, 2020 at 10:20:56AM +0000, Chris Wilson wrote:
> > Quoting Dan Carpenter (2020-01-24 10:13:12)
> > > This is always called with IRQs disabled and we don't actually want to
> > > enable IRQs at the end.
> > > 
> > > Fixes: a6aa8fca4d79 ("dma-buf/sw-sync: Reduce irqsave/irqrestore from known context")
> > > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > > ---
> > >  drivers/dma-buf/sync_debug.c | 5 +++--
> > >  1 file changed, 3 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/dma-buf/sync_debug.c b/drivers/dma-buf/sync_debug.c
> > > index 101394f16930..952331344b1c 100644
> > > --- a/drivers/dma-buf/sync_debug.c
> > > +++ b/drivers/dma-buf/sync_debug.c
> > > @@ -107,15 +107,16 @@ static void sync_print_fence(struct seq_file *s,
> > >  static void sync_print_obj(struct seq_file *s, struct sync_timeline *obj)
> > >  {
> > >         struct list_head *pos;
> > > +       unsigned long flags;
> > >  
> > >         seq_printf(s, "%s: %d\n", obj->name, obj->value);
> > >  
> > > -       spin_lock_irq(&obj->lock);
> > > +       spin_lock_irqsave(&obj->lock, flags);
> > 
> > Exactly, it can be just spin_lock() as the irq state is known.
> > 
> 
> I did consider that but I wasn't sure how this is going to be used in
> the future so I took a conservative approach.

Sure, it's debug so not critical (lists within lists to a seqfile, ouch)

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
-Chris