* Steven Rostedt (rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org) wrote:

On Tue, 2012-08-28 at 19:00 -0400, Mathieu Desnoyers wrote:

quoted

Looking again at:

+#define hash_for_each_size(name, bits, bkt, node, obj, member)                 \
+       for (bkt = 0; bkt < HASH_SIZE(bits); bkt++)                             \
+               hlist_for_each_entry(obj, node, &name[bkt], member)

you will notice that a "break" or "continue" in the inner loop will not
affect the outer loop, which is certainly not what the programmer would
expect!

I advise strongly against creating such error-prone construct.

A few existing loop macros do this. But they require a do { } while ()
approach, and all have a comment.

It's used by do_each_thread() in sched.h 

Yes. It's worth noting that it is a do_each_thread() /
while_each_thread() pair.

and ftrace does this as well.
Look at kernel/trace/ftrace.c at do_for_each_ftrace_rec().

Same here.

Yes it breaks 'break' but it does not break 'continue' as it would just
go to the next item that would have been found (like a normal for
would).

Good point.

So would changing hash_for_each_size() to a

do_each_hash_size()/while_each_hash_size() make it clearer that this
contains a double-loop ? (along with an appropriate comment about
break).

Thanks,

Mathieu

-- Steve

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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