On Mon 2020-08-17 11:26:46, Sergey Senozhatsky wrote: > We have a number of "uart.port->desc.lock vs desc.lock->uart.port" > lockdep reports coming from 8250 driver; this causes a bit of trouble > to people, so let's fix it. > > The problem is reverse lock order in two different call paths: > > chain #1: > > serial8250_do_startup() > spin_lock_irqsave(&port->lock); > disable_irq_nosync(port->irq); > raw_spin_lock_irqsave(&desc->lock) > > chain #2: > > __report_bad_irq() > raw_spin_lock_irqsave(&desc->lock) > for_each_action_of_desc() > printk() > spin_lock_irqsave(&port->lock); > > Fix this by changing the order of locks in serial8250_do_startup(): > do disable_irq_nosync() first, which grabs desc->lock, and grab > uart->port after that, so that chain #1 and chain #2 have same lock > order. > > > Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx> The patch is committed in printk/linux.git, branch for-5.10. Best Regards, Petr
