Nikolay Aleksandrov wrote:

On 11/03/2015 02:57 PM, Jarod Wilson wrote:

quoted

Geert Uytterhoeven wrote:

quoted

On Tue, Nov 3, 2015 at 11:03 AM, Nikolay Aleksandrov
[off-list ref]   wrote:

quoted

On 11/03/2015 03:55 AM, Jarod Wilson wrote:
[snip]

quoted

+#define for_each_netdev_feature(mask_addr, feature)                          \
+     int bit;                                                                \
+     for_each_set_bit(bit, (unsigned long *)mask_addr, NETDEV_FEATURE_COUNT) \
+             feature = __NETIF_F_BIT(bit);
+

^
This is broken, it will not work for more than a single feature.

Indeed it is.

This is used as:

          for_each_netdev_feature(&upper_disables, feature) {
          ...
          }

which expands to:

          int bit;
          for_each_set_bit(bit, (unsigned long *)mask_addr, NETDEV_FEATURE_COUNT)
                  feature = __NETIF_F_BIT(bit);
          {
                  ...
          }

Note the assignment to "feature" happens outside the {}-delimited block.
And the block is always executed once.

Bah, crap, I was still staring at the code not seeing it, thank you for the detailed cluebat. I'll fix that up right now.

Yeah, sorry for not elaborating, I wrote it in a hurry. :-)
Thanks Geert!

By the way since you'll be changing this code, I don't know if it's okay to
declare caller-visible hidden local variables in a macro like this, at the very
least please consider renaming it to something that's much less common, I can see
"bit" being used here and there. IMO either try to find a way to avoid it
altogether or add another argument to the macro so it's explicitly passed.

Just posted a follow-up that removes the macro-internal use of bit and 
doesn't botch up assigning feature. It's not as pretty, but it works 
correctly with multiple feature bits.

-- 
Jarod Wilson
jarod@redhat.com