Messages in this thread | | | Date | Sat, 23 Dec 2017 05:06:21 -0800 | From | Matthew Wilcox <> | Subject | Re: [PATCH 2/2] Introduce __cond_lock_err |
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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). > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
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