On Tue, Jun 18, 2024 at 09:13:05PM GMT, Sibi Sankar wrote:
> The multiple BWMONv4 instances available on the X1E80100 SoC use the
> same interrupt number. Mark them are shared to allow for re-use across
> instances. Handle the ensuing race introduced by relying on bwmon_disable
In an effort to educate the reader, could you please describe what the
race condition is here.
It would also make sense to break this ("Handle...") into a separate
paragraph.
Regards,
Bjorn
> to disable the interrupt and coupled with explicit request/free irqs.
>
> Signed-off-by: Sibi Sankar <quic_sibis@xxxxxxxxxxx>
> ---
>
> v2:
> * Use explicit request/free irq and add comments regarding the race
> introduced when adding the IRQF_SHARED flag. [Krzysztof/Dmitry]
>
> drivers/soc/qcom/icc-bwmon.c | 14 +++++++++++---
> 1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/soc/qcom/icc-bwmon.c b/drivers/soc/qcom/icc-bwmon.c
> index fb323b3364db..4a4e28b41509 100644
> --- a/drivers/soc/qcom/icc-bwmon.c
> +++ b/drivers/soc/qcom/icc-bwmon.c
> @@ -781,9 +781,10 @@ static int bwmon_probe(struct platform_device *pdev)
> bwmon->dev = dev;
>
> bwmon_disable(bwmon);
> - ret = devm_request_threaded_irq(dev, bwmon->irq, bwmon_intr,
> - bwmon_intr_thread,
> - IRQF_ONESHOT, dev_name(dev), bwmon);
> +
> + /* SoCs with multiple cpu-bwmon instances can end up using a shared interrupt line */
> + ret = request_threaded_irq(bwmon->irq, bwmon_intr, bwmon_intr_thread,
> + IRQF_ONESHOT | IRQF_SHARED, dev_name(dev), bwmon);
> if (ret)
> return dev_err_probe(dev, ret, "failed to request IRQ\n");
>
> @@ -798,6 +799,13 @@ static void bwmon_remove(struct platform_device *pdev)
> struct icc_bwmon *bwmon = platform_get_drvdata(pdev);
>
> bwmon_disable(bwmon);
> +
> + /*
> + * Handle the race introduced, when dealing with multiple bwmon instances
> + * using a shared interrupt line, by relying on bwmon_disable to disable
> + * the interrupt and followed by an explicit free.
> + */
> + free_irq(bwmon->irq, bwmon);
> }
>
> static const struct icc_bwmon_data msm8998_bwmon_data = {
> --
> 2.34.1
>
