On Sat, Dec 23, 2017 at 01:39:11AM -0800, Josh Triplett wrote:
> +linux-sparse
Ehh ... we've probably trimmed too much to give linux-sparse a good summary.
Here're the important lines from my patch:
+# define __cond_lock_err(x,c) ((c) ? 1 : ({ __acquire(x); 0; }))
+ return __cond_lock_err(*ptlp, __follow_pte_pmd(mm, address, start, end,
+ ptepp, pmdpp, ptlp));
This is supposed to be "If "c" is an error value, we don't have a lock,
otherwise we have a lock". And to translate from linux-speak into
sparse-speak:
# define __acquire(x) __context__(x,1)
Josh & Ross pointed out (quite correctly) that code which does something like
if (foo())
return;
will work with this, but code that does
if (foo() < 0)
return;
will not because we're now returning 1 instead of -ENOMEM (for example).
So they made the very sensible suggestion that I change the definition
of __cond_lock to:
# define __cond_lock_err(x,c) ((c) ?: ({ __acquire(x); 0; }))
Unfortunately, when I do that, the context imbalance warning returns.
As I said below, this is with sparse 0.5.1.
> On Fri, Dec 22, 2017 at 05:36:34AM -0800, Matthew Wilcox wrote:
> > On Fri, Dec 22, 2017 at 04:31:12AM -0800, Matthew Wilcox wrote:
> > > On Thu, Dec 21, 2017 at 08:21:20PM -0800, Josh Triplett wrote:
> > > > On Thu, Dec 21, 2017 at 05:10:00PM -0800, Matthew Wilcox wrote:
> > > > > Yes, but this define is only #if __CHECKER__, so it doesn't matter what we
> > > > > return as this code will never run.
> > > >
> > > > It does matter slightly, as Sparse does some (very limited) value-based
> > > > analyses. Let's future-proof it.
> > > >
> > > > > That said, if sparse supports the GNU syntax of ?: then I have no
> > > > > objection to doing that.
> > > >
> > > > Sparse does support that syntax.
> > >
> > > Great, I'll fix that and resubmit.
> >
> > Except the context imbalance warning comes back if I do. This is sparse
> > 0.5.1 (Debian's 0.5.1-2 package).
>
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