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/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
