Re: printk() from NMI backtrace can delay a lot

[Sergey Senozhatsky]

On (07/04/18 01:31), Sergey Senozhatsky wrote:
> it might be the case that we can do
> 
> 	serial_driver_handle_irq()
> 	{
> 		spin_loc(uart_port->lock);
> 
> 		.. TX / RX
> 
> 		spin_unlock(uart_port->lock);
> 
> 		tty_flip_buffer_push(uart_port->tty_port);
> 	}
> 
> This should break this chain
> 
> 	uart_port->lock -> pool->lock   // -> sheduler/etc.
> 
> 
> Can we do it? What am I missing?

Hmm, and we actually have some serial drivers that do tty_filp_buffer_push()
outside of uart_port->lock. For instance, drivers/tty/serial/efm32-uart.c
irqreturn_t efm32_uart_rxirq().

	-ss