Does User space/Kernel Space exist in RTOS?
<p>I heard from various kernel developers that most of the RTOSes 
 do not have any separation between user space and kernel space and therefore do not need any context switching.</p>

<p>Is this true? </p>

<p>In the same time, I heard from some other people that it is not true, and RTOSes such as VxWorks or Integrity have separated user mode kernel mode.</p>

<p>Firstly, which of those assumptions are right?</p>

<p>Secondly, if both assumptions are correct, it raises the question that when RTOS vendors use separation between kernel space and user space and when they do not? </p>

<p>Can you name some well-known RTOSes that does not have user mode/kernel mode separation? </p>

<p>Finally, as a side question how they can control the I/O operations and avoid race condition? </p>