Re: UART/TTY console deadlock

[Sergey Senozhatsky]

On (20/07/06 13:31), Kurt Kanzenbach wrote:
> >> @@ -2275,6 +2275,7 @@ int serial8250_do_startup(struct uart_port *port)
> >>
> >>         if (port->irq && !(up->port.flags & UPF_NO_THRE_TEST)) {
> >>                 unsigned char iir1;
> >> +
> >>                 /*
> >>                  * Test for UARTs that do not reassert THRE when the
> >>                  * transmitter is idle and the interrupt has already
> >> @@ -2284,8 +2285,6 @@ int serial8250_do_startup(struct uart_port *port)
> >>                  * allow register changes to become visible.
> >>                  */
> >>                 spin_lock_irqsave(&port->lock, flags);
> >> -               if (up->port.irqflags & IRQF_SHARED)
> >> -                       disable_irq_nosync(port->irq);
> >>
> >>                 wait_for_xmitr(up, UART_LSR_THRE);
> >>                 serial_port_out_sync(port, UART_IER, UART_IER_THRI);
> >> @@ -2297,8 +2296,6 @@ int serial8250_do_startup(struct uart_port *port)
> >>                 iir = serial_port_in(port, UART_IIR);
> >>                 serial_port_out(port, UART_IER, 0);
> >>
> >> -               if (port->irqflags & IRQF_SHARED)
> >> -                       enable_irq(port->irq);
> >>                 spin_unlock_irqrestore(&port->lock, flags);
> >>
> >>                 /*
> >
> > ...which effectively is a revert of
> >
> > 768aec0b5bcc ("serial: 8250: fix shared interrupts issues with SMP and
> > RT kernels")
> 
> Please, don't revert that commit. I've faced the same issue as described
> in the commit log. There is hardware available with shared UART
> interrupt lines.

Will this patch break that hardware?
https://lore.kernel.org/lkml/20200702051213.GB3450@xxxxxxxxxxxxxxxxxxxxxxxx/

	-ss