Commit 048be431 authored Mar 09, 2012 by Rafael J. Wysocki Committed by Paul Mundt Mar 09, 2012

sh-sci / PM: Avoid deadlocking runtime PM



The runtime PM of sh-sci devices is enabled when sci_probe() returns,
so the pm_runtime_put_sync() executed by driver_probe_device()
attempts to suspend the device.  Then, in some situations, a
diagnostic message is printed to the console by one of the runtime
suspend routines handling the sh-sci device, which causes synchronous
runtime resume to be started from the device's own runtime suspend
callback.  This causes rpm_resume() to be run eventually, which sees
the RPM_SUSPENDING status set by rpm_suspend() and waits for it to
change.  However, the device's runtime PM status cannot change at
that point, because the routine that has set it waits for the
rpm_suspend() to return.  A deadlock occurs as a result.

To avoid that make sci_init_single() increment the device's
runtime PM usage counter, so that it cannot be suspended by
driver_probe_device().  That counter has to be decremented
eventually, so make sci_startup() do that before starting to
actually use the device and make sci_shutdown() increment it
again before returning to balance the incrementation carried out by
sci_startup().

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Tested-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

parent 948c46a1

drivers/tty/serial/sh-sci.c

+5 −0

Original line number	Original line	Diff line number	Diff line
	@@ -1710,6 +1710,8 @@ static int sci_startup(struct uart_port *port)

	dev_dbg(port->dev, "%s(%d)\n", __func__, port->line);		dev_dbg(port->dev, "%s(%d)\n", __func__, port->line);

			pm_runtime_put_noidle(port->dev);

	sci_port_enable(s);		sci_port_enable(s);

	ret = sci_request_irq(s);		ret = sci_request_irq(s);
	@@ -1737,6 +1739,8 @@ static void sci_shutdown(struct uart_port *port)
	sci_free_irq(s);		sci_free_irq(s);

	sci_port_disable(s);		sci_port_disable(s);

			pm_runtime_get_noresume(port->dev);
	}		}

	static unsigned int sci_scbrr_calc(unsigned int algo_id, unsigned int bps,		static unsigned int sci_scbrr_calc(unsigned int algo_id, unsigned int bps,
	@@ -2075,6 +2079,7 @@ static int __devinit sci_init_single(struct platform_device *dev,
	sci_init_gpios(sci_port);		sci_init_gpios(sci_port);

	pm_runtime_irq_safe(&dev->dev);		pm_runtime_irq_safe(&dev->dev);
			pm_runtime_get_noresume(&dev->dev);
	pm_runtime_enable(&dev->dev);		pm_runtime_enable(&dev->dev);
	}		}