linux-kernel - Re: [PATCH v6 6/8] PCI: endpoint: pci-epf-test: Don't free doorbell IRQ unless requested

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Message-ID: <wmknyohclurvjq5y7ssuuivjqr7gpy6azttzgjvf2dmhnh3gck@5oeirc4cddtb>
Date: Tue, 10 Feb 2026 10:54:09 +0900
From: Koichiro Den <den@...inux.co.jp>
To: Frank Li <Frank.li@....com>
Cc: vkoul@...nel.org, mani@...nel.org, cassel@...nel.org, 
	jingoohan1@...il.com, lpieralisi@...nel.org, kwilczynski@...nel.org, robh@...nel.org, 
	bhelgaas@...gle.com, kishon@...nel.org, jdmason@...zu.us, allenbh@...il.com, 
	dmaengine@...r.kernel.org, linux-pci@...r.kernel.org, ntb@...ts.linux.dev, 
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 6/8] PCI: endpoint: pci-epf-test: Don't free doorbell
 IRQ unless requested

On Mon, Feb 09, 2026 at 10:57:17AM -0500, Frank Li wrote:
> On Mon, Feb 09, 2026 at 09:53:14PM +0900, Koichiro Den wrote:
> > pci_epf_test_enable_doorbell() allocates a doorbell and then installs
> > the interrupt handler with request_threaded_irq(). On failures before
> > the IRQ is successfully requested (e.g. no free BAR,
> > request_threaded_irq() failure), the error path jumps to
> > err_doorbell_cleanup and calls pci_epf_test_doorbell_cleanup().
> >
> > pci_epf_test_doorbell_cleanup() unconditionally calls free_irq() for the
> > doorbell virq, which can trigger "Trying to free already-free IRQ"
> > warnings when the IRQ was never requested.
> >
> > Track whether the doorbell IRQ has been successfully requested and only
> > call free_irq() when it has.
> >
> > Fixes: eff0c286aa91 ("PCI: endpoint: pci-epf-test: Add doorbell test support")
> > Signed-off-by: Koichiro Den <den@...inux.co.jp>
> > ---
> >  drivers/pci/endpoint/functions/pci-epf-test.c | 9 ++++++++-
> >  1 file changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
> > index 6952ee418622..23034f548c90 100644
> > --- a/drivers/pci/endpoint/functions/pci-epf-test.c
> > +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
> > @@ -86,6 +86,7 @@ struct pci_epf_test {
> >  	bool			dma_private;
> >  	const struct pci_epc_features *epc_features;
> >  	struct pci_epf_bar	db_bar;
> > +	bool			db_irq_requested;
> 
> Prevous patch clean up epf->num_db = 0 at doorbell_free(). can you check
> epf->num_db ?

I don't think so. epf->num_db tracks how many dbs were allocated, but it
doesn't tell whether request_irq() actually succeeded. What I'm fixing here
is the case where the db allocation succeeeds (or was already done), but
the request_irq() fails. In that case we must not call free_irq(), even
though num_db is non-zero. That's why I introduced a separate
db_irq_requested flag.

Thanks for the review,
Koichiro

> 
> Frank
> 
> >  	size_t			bar_size[PCI_STD_NUM_BARS];
> >  };
> >
> > @@ -715,7 +716,10 @@ static void pci_epf_test_doorbell_cleanup(struct pci_epf_test *epf_test)
> >  	struct pci_epf_test_reg *reg = epf_test->reg[epf_test->test_reg_bar];
> >  	struct pci_epf *epf = epf_test->epf;
> >
> > -	free_irq(epf->db_msg[0].virq, epf_test);
> > +	if (epf_test->db_irq_requested && epf->db_msg) {
> > +		free_irq(epf->db_msg[0].virq, epf_test);
> > +		epf_test->db_irq_requested = false;
> > +	}
> >  	reg->doorbell_bar = cpu_to_le32(NO_BAR);
> >
> >  	pci_epf_free_doorbell(epf);
> > @@ -741,6 +745,8 @@ static void pci_epf_test_enable_doorbell(struct pci_epf_test *epf_test,
> >  	if (bar < BAR_0)
> >  		goto err_doorbell_cleanup;
> >
> > +	epf_test->db_irq_requested = false;
> > +
> >  	ret = request_threaded_irq(epf->db_msg[0].virq, NULL,
> >  				   pci_epf_test_doorbell_handler, IRQF_ONESHOT,
> >  				   "pci-ep-test-doorbell", epf_test);
> > @@ -751,6 +757,7 @@ static void pci_epf_test_enable_doorbell(struct pci_epf_test *epf_test,
> >  		goto err_doorbell_cleanup;
> >  	}
> >
> > +	epf_test->db_irq_requested = true;
> >  	reg->doorbell_data = cpu_to_le32(msg->data);
> >  	reg->doorbell_bar = cpu_to_le32(bar);
> >
> > --
> > 2.51.0
> >