Re: [patch v6 3/7] genirq/affinity: Add new callback for (re)calculating interrupt sets

From: Thomas Gleixner <tglx@linutronix.de>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Ming Lei <ming.lei@redhat.com>, Christoph Hellwig <hch@lst.de>,
	Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, Sagi Grimberg <sagi@grimberg.me>,
	linux-nvme@lists.infradead.org, linux-pci@vger.kernel.org,
	Keith Busch <keith.busch@intel.com>,
	Marc Zyngier <marc.zyngier@arm.com>,
	Sumit Saxena <sumit.saxena@broadcom.com>,
	Kashyap Desai <kashyap.desai@broadcom.com>,
	Shivasharan Srikanteshwara 
	<shivasharan.srikanteshwara@broadcom.com>
Subject: Re: [patch v6 3/7] genirq/affinity: Add new callback for (re)calculating interrupt sets
Date: Fri, 18 Jun 2021 21:19:12 +0200	[thread overview]
Message-ID: <878s37f0b3.ffs@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20210615195707.GA2909907@bjorn-Precision-5520>

On Tue, Jun 15 2021 at 14:57, Bjorn Helgaas wrote:
>
>> @@ -1196,6 +1196,13 @@ int pci_alloc_irq_vectors_affinity(struc
>>  	/* use legacy irq if allowed */
>>  	if (flags & PCI_IRQ_LEGACY) {
>>  		if (min_vecs == 1 && dev->irq) {
>> +			/*
>> +			 * Invoke the affinity spreading logic to ensure that
>> +			 * the device driver can adjust queue configuration
>> +			 * for the single interrupt case.
>> +			 */
>> +			if (affd)
>> +				irq_create_affinity_masks(1, affd);
>
> This looks like a leak because irq_create_affinity_masks() returns a
> pointer to kcalloc()ed space, but we throw away the pointer.
>
> Or is there something very subtle going on here, like this special
> case doesn't allocate anything?  I do see the "Nothing to assign?"
> case that returns NULL with no alloc, but it's not completely trivial
> to verify that we take that case here.

Yes, it's subtle and it's subtle crap. Sorry that I did not catch that.

Thanks,

        tglx