On Tue, 2008-04-22 at 20:50 +0200, Jens Axboe wrote:
> +int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
> + int retry, int wait)
> +{
> + unsigned long flags;
> + /* prevent preemption and reschedule on another processor */
> + int me = get_cpu();
> +
> + /* Can deadlock when called with interrupts disabled */
> + WARN_ON(wait && irqs_disabled());
With this fallback to wait the above condition isn't sufficient.
> + if (cpu == me) {
> + local_irq_save(flags);
> + func(info);
> + local_irq_restore(flags);
> + } else {
> + struct call_single_data *data;
> +
> + if (wait) {
> + struct call_single_data d;
> +
> + data = &d;
> + data->flags = CSD_FLAG_WAIT;
> + } else {
> + data = kmalloc(sizeof(*data), GFP_ATOMIC);
> + if (data)
> + data->flags = CSD_FLAG_ALLOC;
> + else {
> + while (test_and_set_bit_lock(0,
> + &cfd_fallback_used))
> + cpu_relax();
> +
> + data = &cfd_fallback.csd;
> + data->flags = CSD_FLAG_FALLBACK;
> + }
> + }
> +
> + data->func = func;
> + data->info = info;
> + generic_exec_single(cpu, data);
> + }
> +
> + put_cpu();
> + return 0;
> +}
> +EXPORT_SYMBOL(smp_call_function_single);
> +int smp_call_function_mask(cpumask_t mask, void (*func)(void *), void *info,
> + int wait)
> +{
> + struct call_function_data *data;
> + cpumask_t allbutself;
> + unsigned long flags;
> + int num_cpus;
> +
> + /* Can deadlock when called with interrupts disabled */
> + WARN_ON(wait && irqs_disabled());
idem
> + allbutself = cpu_online_map;
> + cpu_clear(smp_processor_id(), allbutself);
> + cpus_and(mask, mask, allbutself);
> + num_cpus = cpus_weight(mask);
> +
> + if (!num_cpus)
> + return 0;
> +
> + if (wait) {
> + struct call_function_data d;
> +
> + data = &d;
> + data->csd.flags = CSD_FLAG_WAIT;
> + } else {
> + data = kmalloc(sizeof(*data), GFP_ATOMIC);
> + if (data)
> + data->csd.flags = CSD_FLAG_ALLOC;
> + else {
> + while (test_and_set_bit_lock(0, &cfd_fallback_used))
> + cpu_relax();
> +
> + data = &cfd_fallback;
> + data->csd.flags = CSD_FLAG_FALLBACK;
> + }
> + }
> +
> + spin_lock_init(&data->lock);
> + data->csd.func = func;
> + data->csd.info = info;
> + data->refs = num_cpus;
> + data->cpumask = mask;
> +
> + spin_lock_irqsave(&call_function_lock, flags);
> + list_add_tail_rcu(&data->csd.list, &call_function_queue);
> + spin_unlock_irqrestore(&call_function_lock, flags);
> +
> + /* Send a message to all CPUs in the map */
> + arch_send_call_function_ipi(mask);
> +
> + /* optionally wait for the CPUs to complete */
> + if (wait)
> + csd_flag_wait(&data->csd);
> +
> + return 0;
> +}
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