Commit 829632da authored by Guilherme G. Piccoli's avatar Guilherme G. Piccoli Committed by Helge Deller
Browse files

parisc: Replace regular spinlock with spin_trylock on panic path 



The panic notifiers' callbacks execute in an atomic context, with
interrupts/preemption disabled, and all CPUs not running the panic
function are off, so it's very dangerous to wait on a regular
spinlock, there's a risk of deadlock.

Refactor the panic notifier of parisc/power driver to make use
of spin_trylock - for that, we've added a second version of the
soft-power function. Also, some comments were reorganized and
trailing white spaces, useless header inclusion and blank lines
were removed.

Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Jeroen Roovers <jer@xs4all.nl>
Acked-by: Helge Deller <deller@gmx.de> # parisc
Signed-off-by: default avatarGuilherme G. Piccoli <gpiccoli@igalia.com>
Signed-off-by: default avatarHelge Deller <deller@gmx.de>
parent e0838a99

arch/parisc/include/asm/pdc.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -80,6 +80,7 @@ int pdc_do_firm_test_reset(unsigned long ftc_bitmap); 
int pdc_do_reset(void);

int pdc_do_reset(void);

int pdc_soft_power_info(unsigned long *power_reg);

int pdc_soft_power_info(unsigned long *power_reg);

int pdc_soft_power_button(int sw_control);

int pdc_soft_power_button(int sw_control);

int pdc_soft_power_button_panic(int sw_control);

void pdc_io_reset(void);

void pdc_io_reset(void);

void pdc_io_reset_devices(void);

void pdc_io_reset_devices(void);

int pdc_iodc_getc(void);

int pdc_iodc_getc(void);

arch/parisc/kernel/firmware.c

+23 −4
Original line number Original line Diff line number Diff line
@@ -1232,7 +1232,7 @@ int __init pdc_soft_power_info(unsigned long *power_reg) 
}

}





/*

/*

 * pdc_soft_power_button - Control the soft power button behaviour

 * pdc_soft_power_button{_panic} - Control the soft power button behaviour

 * @sw_control: 0 for hardware control, 1 for software control

 * @sw_control: 0 for hardware control, 1 for software control

 *

 *

 *

 *
@@ -1241,6 +1241,9 @@ int __init pdc_soft_power_info(unsigned long *power_reg) 
 * Under software control the OS may control to when to allow to shut

 * Under software control the OS may control to when to allow to shut

 * down the system. Under hardware control pressing the power button

 * down the system. Under hardware control pressing the power button

 * powers off the system immediately.

 * powers off the system immediately.

 *

 * The _panic version relies on spin_trylock to prevent deadlock

 * on panic path.

 */

 */

int pdc_soft_power_button(int sw_control)

int pdc_soft_power_button(int sw_control)

{

{
@@ -1254,6 +1257,22 @@ int pdc_soft_power_button(int sw_control) 
	return retval;

	return retval;

}

}





int pdc_soft_power_button_panic(int sw_control)

{

	int retval;

	unsigned long flags;



	if (!spin_trylock_irqsave(&pdc_lock, flags)) {

		pr_emerg("Couldn't enable soft power button\n");

		return -EBUSY; /* ignored by the panic notifier */

	}



	retval = mem_pdc_call(PDC_SOFT_POWER, PDC_SOFT_POWER_ENABLE, __pa(pdc_result), sw_control);

	spin_unlock_irqrestore(&pdc_lock, flags);



	return retval;

}



/*

/*

 * pdc_io_reset - Hack to avoid overlapping range registers of Bridges devices.

 * pdc_io_reset - Hack to avoid overlapping range registers of Bridges devices.

 * Primarily a problem on T600 (which parisc-linux doesn't support) but

 * Primarily a problem on T600 (which parisc-linux doesn't support) but

drivers/parisc/power.c

+10 −6
Original line number Original line Diff line number Diff line
@@ -37,7 +37,6 @@ 
#include <linux/module.h>

#include <linux/module.h>

#include <linux/init.h>

#include <linux/init.h>

#include <linux/kernel.h>

#include <linux/kernel.h>

#include <linux/notifier.h>

#include <linux/panic_notifier.h>

#include <linux/panic_notifier.h>

#include <linux/reboot.h>

#include <linux/reboot.h>

#include <linux/sched/signal.h>

#include <linux/sched/signal.h>
@@ -175,16 +174,21 @@ static void powerfail_interrupt(int code, void *x) 












/* parisc_panic_event() is called by the panic handler.

/*

 * As soon as a panic occurs, our tasklets above will not be

 * parisc_panic_event() is called by the panic handler.

 * executed any longer. This function then re-enables the 

 *

 * soft-power switch and allows the user to switch off the system

 * As soon as a panic occurs, our tasklets above will not

 * be executed any longer. This function then re-enables

 * the soft-power switch and allows the user to switch off

 * the system. We rely in pdc_soft_power_button_panic()

 * since this version spin_trylocks (instead of regular

 * spinlock), preventing deadlocks on panic path.

 */

 */

static int parisc_panic_event(struct notifier_block *this,

static int parisc_panic_event(struct notifier_block *this,

		unsigned long event, void *ptr)

		unsigned long event, void *ptr)

{

{

	/* re-enable the soft-power switch */

	/* re-enable the soft-power switch */

	pdc_soft_power_button(0);

	pdc_soft_power_button_panic(0);

	return NOTIFY_DONE;

	return NOTIFY_DONE;

}

}