On Wed, Jun 21, 2017 at 10:59:01AM +0200, Dhananjay Balan wrote:
> Tue, 2017-06-20, 23:05 +0300-യ്ക്ക, Dan Carpenter എഴുതിയിരിക്കുന്നു:
> > On Tue, Jun 20, 2017 at 06:50:13PM +0200, Dhananjay Balan wrote:
> > > The locking and unlocking code used by copy routines is common, so
> > > moved it to a macro.
> > >
> > > Signed-off-by: Dhananjay Balan <mail@xxxxxxxxx>
> > > ---
> > > drivers/staging/sm750fb/sm750.c | 81 ++++++++++++++++-------------
> > > ------------
> > > 1 file changed, 31 insertions(+), 50 deletions(-)
> > >
> > > diff --git a/drivers/staging/sm750fb/sm750.c
> > > b/drivers/staging/sm750fb/sm750.c
> > > index 386d4adcd91d..d8ab83aea46d 100644
> > > --- a/drivers/staging/sm750fb/sm750.c
> > > +++ b/drivers/staging/sm750fb/sm750.c
> > > @@ -156,12 +156,25 @@ static int lynxfb_ops_cursor(struct fb_info
> > > *info, struct fb_cursor *fbcursor)
> > > return 0;
> > > }
> > >
> > > +/*
> > > + * If not using spin_lock, system will die if user frequently
> > > loads and
> > > + * immediately unloads driver (dual)
> > > + */
> > > +#define dual_safe_call(func, ...)
> > > \
> > > + do {
> > > \
> > > + if (sm750_dev->fb_count > 1)
> > > \
> > > + spin_lock(&sm750_dev->slock);
> > > \
> > > + func(__VA_ARGS__);
> > > \
> > > + if (sm750_dev->fb_count > 1)
> > > \
> > > + spin_unlock(&sm750_dev->slock);
> > > \
> > > + } while (0)
> > > +
> >
> > I feel like this is the wrong approach. You could just make a small
> > lock function and a small unlock function. Except that if statement
> > seems kind of bogus. What happens if ->fb_count is 0 when we lock
> > and
> > 1 when we unlock? Why not lock unconditionally? It is not likely to
> > be
> > contested if there are no other users.
> I've to admit that I don't have much info, but is fb_count supposed to
> change during this execution?
It could change, yes.
regards,
dan carpenter
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