在 2015年1月30日，20:43，"Matwey V. Kornilov" <matwey.kornilov@gmail.com> 写道：
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.
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.
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