On Mon, Aug 17, 2020 at 12:40:03PM +0100, Jim Baxter wrote: > We have issues with the workqueue of the kernel overloading the CPU 0 > when we we disconnect a USB stick. Do you unmount the stick before disconnecting it? > This results in other items on the shared workqueue being delayed by > around 6.5 seconds with a default kernel configuration and 2.3 seconds > on a config tailored for our RCar embedded platform. > > I am aware there will be delays on the shared workqueue, are the delays > we are seeing considered normal? Assuming the workqueue delay is caused by the USB subsystem, you may be able to get more information by turning on USB dynamic debugging: echo 'module usbcore =p' >/sys/kernel/debug/dynamic_debug/control and seeing what shows up in the dmesg log. One long-running job should not normally be enough to delay an entire workqueues. Workqueues are allowed to spawn multiple threads; they are supposed to resize themselves dynamically as required. Alan Stern
