Spinlocks imply memory barriers as far as I am aware...

Read here: 
http://lxr.free-electrons.com/source/Documentation/memory-barriers.txt#L1634

On 30/01/15 14:20, Matwey V. Kornilov wrote:

2015-01-30 16:52 GMT+03:00 buyitian [off-list ref]:

quoted

Please check the assembly code to double confirm the GCC behavior.
Why will GCC change the order as what you mentioned? Only assembly code can tell you.

It does not change at the moment. I think it can change it.

Because from line
   ret = hdl->count;
until line
   return ret;
there is no access to either ret or hdl->count. So it is reasonable to
optimizer to think that their values are the same and eliminate
unneeded variable.