On Thu, 18 Oct 2007 11:25:42 +1000 Benjamin Herrenschmidt <[EMAIL PROTECTED]> wrote:
> synchronize_irq needs at the very least a compiler barrier and a > read barrier on SMP, Why? > but there are enough cases around where a > write barrier is also needed and it's not a hot path so I prefer > using a full smp_mb() here. > > It will degrade to a compiler barrier on !SMP. > > Signed-off-by: Benjamin Herrenschmidt <[EMAIL PROTECTED]> > --- > > Index: linux-work/kernel/irq/manage.c > =================================================================== > --- linux-work.orig/kernel/irq/manage.c 2007-10-18 11:22:16.000000000 > +1000 > +++ linux-work/kernel/irq/manage.c 2007-10-18 11:22:20.000000000 +1000 > @@ -33,6 +33,7 @@ void synchronize_irq(unsigned int irq) > if (irq >= NR_IRQS) > return; > > + smp_mb(); > while (desc->status & IRQ_INPROGRESS) > cpu_relax(); > } Anyone reading this code is going to ask "wtf is that for". It needs a comment telling them. mb() is the new lock_kernel(). Sigh. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
