Re: [PATCH v10 4/5] core: Add kernel message dumper to call on oopses and panics

Ingo Molnar
2009-10-16T10:11:50Z

* Simon Kagstrom <simon.kagstrom@netinsight.net> wrote:

> +int kmsg_dump_register(struct kmsg_dumper *dumper)
> +{
> + unsigned long flags;
> +
> + /* The dump callback needs to be set */
> + if (!dumper->dump)
> + return -EINVAL;
> +
> + spin_lock_irqsave(&dump_list_lock, flags);
> +
> + /* Don't allow registering multiple times */
> + if (dumper->registered) {
> + spin_unlock_irqrestore(&dump_list_lock, flags);
> +
> + return -EBUSY;
> + }
> +
> + dumper->registered = 1;
> + list_add(&dumper->list, &dump_list);
> + spin_unlock_irqrestore(&dump_list_lock, flags);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(kmsg_dump_register);

i dont want to bikeshed paint this but this sequence caught my eyes. We
generally do flatter and clearer locking sequences:

int kmsg_dump_register(struct kmsg_dumper *dumper)
{
unsigned long flags;
int err = -EBUSY;

/* The dump callback needs to be set */
if (!dumper->dump)
return -EINVAL;

spin_lock_irqsave(&dump_list_lock, flags);

/* Don't allow registering multiple times */
if (!dumper->registered) {
dumper->registered = 1;
list_add_tail(&dumper->list, &dump_list);
err = 0;
}

spin_unlock_irqrestore(&dump_list_lock, flags);

return err;
}
EXPORT_SYMBOL_GPL(kmsg_dump_register);

(warning: untested, written in mail editor)

Same goes for kmsg_dump_unregister().

Ingo