Re: [PATCH 1/2] x86-64 TIF flags for debug regs and io bitmap in ctxsw

[Stephane Eranian]

Arjan,

On Tue, Jul 04, 2006 at 09:51:49AM +0200, Arjan van de Ven wrote:
> > -		}
> > -	}
> > +	if (unlikely((task_thread_info(next_p)->flags & _TIF_WORK_CTXSW))
> > +	    || test_tsk_thread_flag(prev_p, TIF_IO_BITMAP))
> > +		__switch_to_xtra(prev_p, next_p, tss);
> 
> well isn't this replacing an if() (which isn't cheap but also not
> expensive, due to unlikely()) with an atomic operation (which *is*
> expensive) ?
> 
Andi is right. I double checked the test_tsk_thread_flag() and it does not
use atomic ops.

-- 
-Stephane
-
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