Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Date:   Fri, 3 Jul 2020 19:32:41 +0900
To:     Tony Lindgren <tony@atomide.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Petr Mladek <pmladek@suse.com>,
        Andy Shevchenko <andy.shevchenko@gmail.com>,
        Raul Rangel <rrangel@google.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        kurt@linutronix.de, "S, Shirish" <Shirish.S@amd.com>,
        Peter Zijlstra <peterz@infradead.org>,
        John Ogness <john.ogness@linutronix.de>,
        Steven Rostedt <rostedt@goodmis.org>
Subject: Re: UART/TTY console deadlock
Message-ID: <20200703103241.GB182102@jagdpanzerIV.localdomain>
References: <CAHQZ30BnfX+gxjPm1DUd5psOTqbyDh4EJE=2=VAMW_VDafctkA@mail.gmail.com>
 <CAHp75Vd8nTzmZdnhpTDChdc11zyCaSfeigbxaCpOWZ1Lv9ZBMw@mail.gmail.com>
 <20200630035816.GA21591@jagdpanzerIV.localdomain>
 <20200630102141.GA11587@alley>
 <20200630105512.GA530@jagdpanzerIV.localdomain>
 <20200630122239.GD6173@alley>
 <20200630130534.GB145027@jagdpanzerIV.localdomain>
 <20200630180255.GD37466@atomide.com>
 <20200702051213.GB3450@jagdpanzerIV.localdomain>
 <20200702160514.GK37466@atomide.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20200702160514.GK37466@atomide.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On (20/07/02 09:05), Tony Lindgren wrote:
> * Sergey Senozhatsky <sergey.senozhatsky@gmail.com> [200702 05:13]:
> > On (20/06/30 11:02), Tony Lindgren wrote:
> > > This conditional disable for irq_shared does not look nice to me
> > > from the other device point of view :)
> > > 
> > > Would it be possible to just set up te dummy interrupt handler
> > > for the startup, then change it back afterwards? See for example
> > > omap8250_no_handle_irq().
> > 
> > I think we can do it. serial8250_do_startup() and irq handler take
> > port->lock, so they should be synchronized.
> > 
> > Something like this then?
> 
> Yeah thanks this should work better for shared irq.

This is, basically, an equivalent of

---
 drivers/tty/serial/8250/8250_port.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index d64ca77d9cfa..dba7747d2ddd 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -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);
 
 		/*
-- 
2.27.0