reason for code like this: "do { something } while (0)"

["Rajat Jain" <rajat.noida.india@xxxxxxxxx>]

Hi,

I'm asking a pretty amateur question.

I've come accross code like this huge number of times in the kernel:

#define __set_task_state(tsk, state_value)              \
       do { (tsk)->state = (state_value); } while (0)

What is the reason to use do while loop if it is only meant to be
executed just once? Why not a simple:

#define __set_task_state(tsk, state_value)              \
       { (tsk)->state = (state_value); }

TIA,

Rajat
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