Messages in this thread Patch in this message | | | Date | Fri, 22 Sep 2023 11:50:32 +0200 | From | Sascha Hauer <> | Subject | Re: [PATCH] dmaengine: imx-sdma: fix deadlock in interrupt handler |
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Hi Tim,
On Thu, Sep 21, 2023 at 09:57:11AM +0000, Tim van der Staaij | Zign wrote: > dev_warn internally acquires the lock that is already held when > sdma_update_channel_loop is called. Therefore it is acquired twice and > this is detected as a deadlock. Temporarily release the lock while > logging to avoid this. > > Signed-off-by: Tim van der Staaij <tim.vanderstaaij@zigngroup.com> > Link: https://lore.kernel.org/all/AM0PR08MB308979EC3A8A53AE6E2D3408802CA@AM0PR08MB3089.eurprd08.prod.outlook.com/ > --- > drivers/dma/imx-sdma.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c > index 51012bd39900..3a7cd783a567 100644 > --- a/drivers/dma/imx-sdma.c > +++ b/drivers/dma/imx-sdma.c > @@ -904,7 +904,10 @@ static void sdma_update_channel_loop(struct sdma_channel *sdmac) > * owned buffer is available (i.e. BD_DONE was set too late). > */ > if (sdmac->desc && !is_sdma_channel_enabled(sdmac->sdma, sdmac->channel)) { > + spin_unlock(&sdmac->vc.lock); > dev_warn(sdmac->sdma->dev, "restart cyclic channel %d\n", sdmac->channel); > + spin_lock(&sdmac->vc.lock);
This is strange. Why and how does dev_warn() call back into the SDMA driver?
We shouldn't merge this without having a clue what exactly goes wrong here. Please provide the corresponding lockdep output.
Sascha
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