5.4-stable review patch. If anyone has any objections, please let me know.
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From: Duoming Zhou duoming@zju.edu.cn
[ Upstream commit 01f1ae2733e2bb4de92fefcea5fda847d92aede1 ]
The synchronize_irq(c->irq) will not return until the IRQ handler mtk_uart_apdma_irq_handler() is completed. If the synchronize_irq() holds a spin_lock and waits the IRQ handler to complete, but the IRQ handler also needs the same spin_lock. The deadlock will happen. The process is shown below:
cpu0 cpu1 mtk_uart_apdma_device_pause() | mtk_uart_apdma_irq_handler() spin_lock_irqsave() | | spin_lock_irqsave() //hold the lock to wait | synchronize_irq() |
This patch reorders the synchronize_irq(c->irq) outside the spin_lock in order to mitigate the bug.
Fixes: 9135408c3ace ("dmaengine: mediatek: Add MediaTek UART APDMA support") Signed-off-by: Duoming Zhou duoming@zju.edu.cn Reviewed-by: Eugen Hristev eugen.hristev@collabora.com Link: https://lore.kernel.org/r/20230806032511.45263-1-duoming@zju.edu.cn Signed-off-by: Vinod Koul vkoul@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/dma/mediatek/mtk-uart-apdma.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/dma/mediatek/mtk-uart-apdma.c b/drivers/dma/mediatek/mtk-uart-apdma.c index 7718d09e3d29f..5d1ba3ba3755a 100644 --- a/drivers/dma/mediatek/mtk-uart-apdma.c +++ b/drivers/dma/mediatek/mtk-uart-apdma.c @@ -450,9 +450,8 @@ static int mtk_uart_apdma_device_pause(struct dma_chan *chan) mtk_uart_apdma_write(c, VFF_EN, VFF_EN_CLR_B); mtk_uart_apdma_write(c, VFF_INT_EN, VFF_INT_EN_CLR_B);
- synchronize_irq(c->irq); - spin_unlock_irqrestore(&c->vc.lock, flags); + synchronize_irq(c->irq);
return 0; }