linux-kernel - Re: [PATCH v3] interconnect: avoid memory allocation when 'icc_bw

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Message-ID: <aFvuiVX0kMIqXQtZ@hovoldconsulting.com>
Date: Wed, 25 Jun 2025 14:41:45 +0200
From: Johan Hovold <johan@...nel.org>
To: Gabor Juhos <j4g8y7@...il.com>
Cc: Georgi Djakov <djakov@...nel.org>,
	Raviteja Laggyshetty <quic_rlaggysh@...cinc.com>,
	Johan Hovold <johan+linaro@...nel.org>,
	Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
	linux-pm@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] interconnect: avoid memory allocation when
 'icc_bw_lock' is held

On Wed, Jun 25, 2025 at 02:30:15PM +0200, Johan Hovold wrote:
> On Wed, Jun 25, 2025 at 01:25:04PM +0200, Gabor Juhos wrote:

> > @@ -276,13 +276,17 @@ int qcom_icc_rpmh_probe(struct platform_device *pdev)
> >  		qcom_icc_bcm_init(qp->bcms[i], dev);
> >  
> >  	for (i = 0; i < num_nodes; i++) {
> > +		bool is_dyn_node = false;
> > +
> >  		qn = qnodes[i];
> >  		if (!qn)
> >  			continue;
> >  
> >  		if (desc->alloc_dyn_id) {
> > -			if (!qn->node)
> > +			if (!qn->node) {
> 
> AFAICS, qn->node will currently never be set here and I'm not sure why
> commit 7f9560a3bebe ("interconnect: qcom: icc-rpmh: Add dynamic icc node
> id support") added this check, or even the node field to struct
> qcom_icc_desc for that matter.
> 
> But if there's some future use case for this, then you may or may not
> need to make sure that a name is allocated also in that case.

Ok, I see what's going on. The qn->node may have been (pre-) allocated
in icc_link_nodes() dynamically, which means you need to make sure to
generate a name also in that case.

> And that could be done by simply checking if node->id >=
> ICC_DYN_ID_START instead of using a boolean flag below. That may be
> preferred either way.

So you should probably use node->id to determine this.

Johan