From 32310aaf5c410dd3dc701556cc9bbeff0847c7c9 Mon Sep 17 00:00:00 2001 From: Murali Karicheri Date: Fri, 21 Dec 2012 15:13:26 -0500 Subject: [PATCH] spi/davinci: use request_threaded_irq() to fix deadlock With RT pre-empt patch applied to Linux kernel, the irq handler will be force converted to an irq thread. spi driver can get back to back messages from the slave device. In such cases, IRQ thread doesn't get a chance to run to read the slave data. Hence the irq handler must be run in hard irq context to read/write data from slave device. Otherwise, the kernel goes into a deadlock. This patch fixes this issue when PREEMPT_RT_FULL is enabled in the kernel. A dummy thread function is provided to satisfy the request_threaded_irq() API. Passing a NULL for function also causes the irq handler to be executed in the thread context. Signed-off-by: Murali Karicheri Signed-off-by: Grant Likely --- drivers/spi/spi-davinci.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/drivers/spi/spi-davinci.c b/drivers/spi/spi-davinci.c index 50bd2cdc52de..8234d2259722 100644 --- a/drivers/spi/spi-davinci.c +++ b/drivers/spi/spi-davinci.c @@ -701,6 +701,19 @@ err_alloc_dummy_buf: return ret; } +/** + * dummy_thread_fn - dummy thread function + * @irq: IRQ number for this SPI Master + * @context_data: structure for SPI Master controller davinci_spi + * + * This is to satisfy the request_threaded_irq() API so that the irq + * handler is called in interrupt context. + */ +static irqreturn_t dummy_thread_fn(s32 irq, void *data) +{ + return IRQ_HANDLED; +} + /** * davinci_spi_irq - Interrupt handler for SPI Master Controller * @irq: IRQ number for this SPI Master @@ -899,8 +912,8 @@ static int davinci_spi_probe(struct platform_device *pdev) goto unmap_io; } - ret = request_irq(dspi->irq, davinci_spi_irq, 0, dev_name(&pdev->dev), - dspi); + ret = request_threaded_irq(dspi->irq, davinci_spi_irq, dummy_thread_fn, + 0, dev_name(&pdev->dev), dspi); if (ret) goto unmap_io; -- 2.39.5