Re: [PATCH v3] PCI: endpoint: pci-epf-test: Fix sleeping function being called from atomic context

[Frank Li <Frank.li@nxp.com>]

On Tue, Oct 14, 2025 at 08:11:09AM +0530, 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.
>
> BUG: sleeping function called from invalid context at kernel/locking/mutex.c:271
> Call trace:
>  __might_resched+0x130/0x158
>  __might_sleep+0x70/0x88
>  mutex_lock+0x2c/0x80
>  pci_epc_get_msi+0x78/0xd8
>  pci_epf_test_raise_irq.isra.0+0x74/0x138
>  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@gmail.com>
> Reviewed-by: Niklas Cassel <cassel@kernel.org>

Reviewed-by: Frank Li <Frank.Li@nxp.com>

> ---
>  Note : The patch is compiled and tested on TI am642 board.
>
>  Change log
>  V2->V3:
>   Addressed Bjorn Helgass review points in v2
>   - Rebase to pci/main (v6.18-rc1)
>   - Add a space before each "("
>   - Remove the timestamps because they're unnecessary distraction
>   - Add "()" after function names in commit log
>   - s/irq/IRQ/
>   - Rewrap the commit log to fit in 75 columns
>   - Rewrap the code below to fit in 78 columns because most of the
>     rest of the file does
>   Link to V2: https://lore.kernel.org/all/20250930023809.7931-1-bhanuseshukumar@gmail.com/
>
>  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/
>
>  drivers/pci/endpoint/functions/pci-epf-test.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
> index 31617772a..b05e8db57 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-test.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
> @@ -730,8 +730,9 @@ 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",
> --
> 2.34.1
>