On 10.03.2021 07:46:26, Daniel Glöckner wrote: > the mcp251xfd driver uses a threaded irq handler to queue skbs with the > can_rx_offload_* helpers. I get the following error on every packet until > the rate limit kicks in: > > NOHZ tick-stop error: Non-RCU local softirq work is pending, handler > #08!!! That's a known problem. But I had no time to investigate it. > Adding local_bh_disable/local_bh_enable around the can_rx_offload_* calls > gets rid of the error, but is that the correct way to fix this? > Internally the can_rx_offload code uses spin_lock_irqsave to safely > manipulate its queue. The problem is not the queue handling inside of rx_offload, but the call to napi_schedule(). This boils down to raising a soft IRQ (the NAPI) from the threaded IRQ handler of the mcp251xfd driver. The local_bh_enable() "fixes" the problem running the softirq if needed. https://elixir.bootlin.com/linux/v5.11/source/kernel/softirq.c#L1913 I'm not sure how to properly fix the problem, yet. regards, Marc -- Pengutronix e.K. | Marc Kleine-Budde | Embedded Linux | https://www.pengutronix.de | Vertretung West/Dortmund | Phone: +49-231-2826-924 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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