Re: [PATCH 02/23] interconnect: fix icc_provider_del() error handling

Konrad Dybcio
2023-02-01T11:17:01Z

On 1.02.2023 11:15, Johan Hovold wrote:
> The interconnect framework currently expects that providers are only
> removed when there are no users and after all nodes have been removed.
>
> There is currently nothing that guarantees this to be the case and the
> framework does not do any reference counting, but refusing to remove the
> provider is never correct as that would leave a dangling pointer to a
> resource that is about to be released in the global provider list (e.g.
> accessible through debugfs).
>
> Replace the current sanity checks with WARN_ON() so that the provider is
> always removed.
I spent a considerable amount of time scratching my head what WARN_ON has
to do with removing list items.. I suppose "don't return early and replace
pr_warn with WARN_ON" would have been clearer, but maybe that's just me
in the morning..

>
> Fixes: 11f1ceca7031 ("interconnect: Add generic on-chip interconnect API")
> Cc: stable@vger.kernel.org # 5.1: 680f8666baf6: interconnect: Make icc_provider_del() return void
> Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
> ---
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>

Konrad
> drivers/interconnect/core.c | 14 ++------------
> 1 file changed, 2 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/interconnect/core.c b/drivers/interconnect/core.c
> index dc61620a0191..43c5c8503ee8 100644
> --- a/drivers/interconnect/core.c
> +++ b/drivers/interconnect/core.c
> @@ -1062,18 +1062,8 @@ EXPORT_SYMBOL_GPL(icc_provider_add);
> void icc_provider_del(struct icc_provider *provider)
> {
> mutex_lock(&icc_lock);
> - if (provider->users) {
> - pr_warn("interconnect provider still has %d users\n",
> - provider->users);
> - mutex_unlock(&icc_lock);
> - return;
> - }
> -
> - if (!list_empty(&provider->nodes)) {
> - pr_warn("interconnect provider still has nodes\n");
> - mutex_unlock(&icc_lock);
> - return;
> - }
> + WARN_ON(provider->users);
> + WARN_ON(!list_empty(&provider->nodes));
>
> list_del(&provider->provider_list);
> mutex_unlock(&icc_lock);