linux-kernel - Re: [RFC v2 06/16] luo: luo_subsystems: add subsystem registration

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Message-ID: <CALzav=dzvVgmwxhh9ic6mTjQL32srzAOH-wXgkksXTa2rd=TNw@mail.gmail.com>
Date: Wed, 28 May 2025 12:12:38 -0700
From: David Matlack <dmatlack@...gle.com>
To: Pasha Tatashin <pasha.tatashin@...een.com>
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Subject: Re: [RFC v2 06/16] luo: luo_subsystems: add subsystem registration

On Thu, May 15, 2025 at 11:23 AM Pasha Tatashin
<pasha.tatashin@...een.com> wrote:
>
> +int liveupdate_register_subsystem(struct liveupdate_subsystem *h)
> +{
> +       struct liveupdate_subsystem *iter;
> +       int ret = 0;
> +
> +       luo_state_read_enter();
> +       if (!liveupdate_state_normal() && !liveupdate_state_updated()) {
> +               luo_state_read_exit();
> +               return -EBUSY;
> +       }
> +
> +       mutex_lock(&luo_subsystem_list_mutex);
> +       list_for_each_entry(iter, &luo_subsystems_list, list) {
> +               if (iter == h) {
> +                       pr_warn("Subsystem '%s' (%p) already registered.\n",
> +                               h->name, h);
> +                       ret = -EEXIST;
> +                       goto out_unlock;
> +               }
> +
> +               if (!strcmp(iter->name, h->name)) {
> +                       pr_err("Subsystem with name '%s' already registered.\n",
> +                              h->name);
> +                       ret = -EEXIST;
> +                       goto out_unlock;
> +               }
> +       }
> +
> +       INIT_LIST_HEAD(&h->list);
> +       list_add_tail(&h->list, &luo_subsystems_list);
> +
> +out_unlock:
> +       mutex_unlock(&luo_subsystem_list_mutex);
> +       luo_state_read_exit();
> +
> +       return ret;
> +}

Suggest using guard()() and scoped_guard() throughout this series
instead of manual lock/unlock and up/down. That will simplify the code
and reduce the chance of silly bugs where a code path misses an
unlock/down.