Re: Inconsistency in changing the state of task ??
Thu, 06 Mar 2003 06:11:30 -0700

Thanks Robert for the reply.
But I notice that __set_current_state() is same as current->state. So, I
didn't understand the safety factor on using __set_current_state( ).

Also why should I use __set_current_state() instead of set_current_state()
when the later is SMP safe.

Thanks in advance....

Robert Love writes:

> On Tue, 2003-03-04 at 03:36, wrote:
>> while browsing through fs/select.c file of 2.4.19, I came across two
>> DIFFERENT ways of changing the state of the current task in do_select():
>> set_current_state = TASK_INTERRUPTIBLE;
>> AND current->state = TASK_RUNNING;
>> I am curious to know if the second line of code doesn't cause any problem in
>> SMP systems. I also see the same situation in do_poll().
> You normally want to use set_current_state(), which is a nice
> abstraction and safe for SMP.
> Sometimes it is safe to use __set_current_state(), which does not
> provide a memory barrier.
> The above open-coded line can be changed to
> __set_current_state(TASK_RUNNING).
> Robert Love

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