Re: [PATCH] MIPS: add smp_call_function_single()

Heiko Carstens
2007-07-28T09:20:36Z

On Fri, Jul 27, 2007 at 06:53:23AM -0700, Stephane Eranian wrote:
> Ralf,
>
> Here is take 2.
>
> [MIPS] add smp_call_function_single (take 2)
>
> signed-off-by: Stephane Eranian <eranian@hpl.hp.com>
> signed-off-by: Phil Mucci <mucci@cs.utk.edu>
>
> diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c
> index be7362b..d47234c 100644
> --- a/arch/mips/kernel/smp.c
> +++ b/arch/mips/kernel/smp.c
> @@ -193,6 +193,53 @@ void smp_call_function_interrupt(void)
> }
> }
>
> +int smp_call_function_single(int cpu, void (*func) (void *info), void *info, int retry,
> + int wait)
> +{
> + struct call_data_struct data;
> + int me = smp_processor_id();
> +
> + /*
> + * Can die spectacularly if this CPU isn't yet marked online
> + */
> + BUG_ON(!cpu_online(me));
> + if (cpu == me) {
> + WARN_ON(1);
> + return -EBUSY;
> + }
> +
> + /* Can deadlock when called with interrupts disabled */
> + WARN_ON(irqs_disabled());
> +
> + data.func = func;
> + data.info = info;
> + atomic_set(&data.started, 0);
> + data.wait = wait;
> + if (wait)
> + atomic_set(&data.finished, 0);
> +
> + spin_lock(&smp_call_lock);
> + call_data = &data;
> + mb();
> +
> + /* Send a message to the other CPU */
> + core_send_ipi(cpu, SMP_CALL_FUNCTION);
> +
> + /* Wait for response */
> + /* FIXME: lock-up detection, backtrace on lock-up */
> + while (atomic_read(&data.started) != 1)
> + barrier();
> +
> + if (wait)
> + while (atomic_read(&data.finished) != 1)
> + barrier();
> + call_data = NULL;
> + spin_unlock(&smp_call_lock);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(smp_call_function_single);
> +
> static void stop_this_cpu(void *dummy)
> {

This will not do the right thing. Semantics of smp_call_function_single()
changed recently. It now is supposed to call func() locally with irqs
disabled if cpu == smp_processor_id(). See i386/x86_64 and powerpc.
Unfortunately ia64 hasn't been changed yet, so it will behave differently.