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Message-ID: <162ad81c-a203-4196-985d-b48a6afeb4d7@gmail.com>
Date: Thu, 9 Oct 2025 11:21:17 +0530
From: Bhanu Seshu Kumar Valluri <bhanuseshukumar@...il.com>
To: mani@...nel.org, kwilczynski@...nel.org, kishon@...nel.org,
bhelgaas@...gle.com, cassel@...nel.org, Frank.Li@....com,
dlemoal@...nel.org, christian.bruel@...s.st.com
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
bhanuseshukumar@...il.com
Subject: Re: [PATCH v2] PCI: endpoint: pci-epf-test: Fix sleeping function
being called from atomic context
On 30/09/25 08:08, Bhanu Seshu Kumar Valluri wrote:
> When Root Complex(RC) triggers a Doorbell MSI interrupt to Endpoint(EP) it triggers a warning
> in the EP. pci_endpoint kselftest target is compiled and used to run the Doorbell test in RC.
>
> [ 474.686193] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:271
> [ 474.710934] Call trace:
> [ 474.710995] __might_resched+0x130/0x158
> [ 474.711011] __might_sleep+0x70/0x88
> [ 474.711023] mutex_lock+0x2c/0x80
> [ 474.711036] pci_epc_get_msi+0x78/0xd8
> [ 474.711052] pci_epf_test_raise_irq.isra.0+0x74/0x138
> [ 474.711063] pci_epf_test_doorbell_handler+0x34/0x50
>
> The BUG arises because the EP's pci_epf_test_doorbell_handler is making an
> indirect call to pci_epc_get_msi, which uses mutex inside, from interrupt context.
>
> To fix the issue convert hard irq handler to a threaded irq handler to allow it
> to call functions that can sleep during bottom half execution. Register threaded
> irq handler with IRQF_ONESHOT to keep interrupt line disabled until the threaded
> irq handler completes execution.
>
> Fixes: eff0c286aa91 ("PCI: endpoint: pci-epf-test: Add doorbell test support")
> Signed-off-by: Bhanu Seshu Kumar Valluri <bhanuseshukumar@...il.com>
> ---
> Note : It is compiled and tested on TI am642 board.
>
> Change log. V1->V2:
> Trimmed Call trace to include only essential calls.
> Used 12 digit commit ID in fixes tag.
> Steps to reproduce the bug are removed from commit log.
> Link to V1: https://lore.kernel.org/all/20250917161817.15776-1-bhanuseshukumar@gmail.com/
>
> Warnings can be reproduced by following steps below.
> *On EP side:
> 1. Configure the pci-epf-test function using steps given below
> mount -t configfs none /sys/kernel/config
> cd /sys/kernel/config/pci_ep/
> mkdir functions/pci_epf_test/func1
> echo 0x104c > functions/pci_epf_test/func1/vendorid
> echo 0xb010 > functions/pci_epf_test/func1/deviceid
> echo 32 > functions/pci_epf_test/func1/msi_interrupts
> echo 2048 > functions/pci_epf_test/func1/msix_interrupts
> ln -s functions/pci_epf_test/func1 controllers/f102000.pcie-ep/
> echo 1 > controllers/f102000.pcie-ep/start
>
> *On RC side:
> 1. Once EP side configuration is done do pci rescan.
> echo 1 > /sys/bus/pci/rescan
> 2. Run Doorbell MSI test using pci_endpoint_test kselftest app.
> ./pci_endpoint_test -r pcie_ep_doorbell.DOORBELL_TEST
> Note: Kernel is compiled with CONFIG_DEBUG_KERNEL enabled.
>
> drivers/pci/endpoint/functions/pci-epf-test.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
> index e091193bd8a8..c9e2eb930ad3 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-test.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
> @@ -725,8 +725,8 @@ static void pci_epf_test_enable_doorbell(struct pci_epf_test *epf_test,
> if (bar < BAR_0)
> goto err_doorbell_cleanup;
>
> - ret = request_irq(epf->db_msg[0].virq, pci_epf_test_doorbell_handler, 0,
> - "pci-ep-test-doorbell", epf_test);
> + ret = request_threaded_irq(epf->db_msg[0].virq, NULL, pci_epf_test_doorbell_handler,
> + IRQF_ONESHOT, "pci-ep-test-doorbell", epf_test);
> if (ret) {
> dev_err(&epf->dev,
> "Failed to request doorbell IRQ: %d\n",
Hi,
I just wanted to check if you had a chance to review it or if any changes are needed from my side.
Regards,
Bhanu Seshu Kumar Valluri
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