spinlock variable protection

Matwey V. Kornilov matwey.kornilov at gmail.com
Fri Jan 30 07:43:40 EST 2015


Hi,

I have the following code

         int ret = 0;
         unsigned long irqflags;

         spin_lock_irqsave(&lock, irqflags);

         //...
         ret = hdl->count;
         //...

         spin_unlock_irqrestore(&lock, irqflags);
         return ret;

I would like to be sure, that ret will not be optimized out. I think 
compiler can convert the code to equivalent:

         unsigned long irqflags;

         spin_lock_irqsave(&lock, irqflags);

         //...
         //...

         spin_unlock_irqrestore(&lock, irqflags);
         return hdl->count;

But this is not what I want, because I use lock to protect hdl and want 
to return hdl->count value as it was in protected section.




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