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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: Guilherme G. Piccoli <gpiccoli@igalia.com>
Signed-off-by: Helge Deller <deller@gmx.de>
This commit is contained in:
Guilherme G. Piccoli 2023-02-20 18:11:05 -03:00 committed by Helge Deller
parent e0838a9928
commit 829632dae8
3 changed files with 34 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/parisc/include/asm/pdc.h
View File

@ -80,6 +80,7 @@ int pdc_do_firm_test_reset(unsigned long ftc_bitmap);
int pdc_do_reset(void);
int pdc_soft_power_info(unsigned long *power_reg);
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_devices(void);
int pdc_iodc_getc(void);

27
arch/parisc/kernel/firmware.c
View File

@ -1232,15 +1232,18 @@ int __init pdc_soft_power_info(unsigned long *power_reg)
}
/*
* pdc_soft_power_button - Control the soft power button behaviour
* @sw_control: 0 for hardware control, 1 for software control
* pdc_soft_power_button{_panic} - Control the soft power button behaviour
* @sw_control: 0 for hardware control, 1 for software control
*
*
* This PDC function places the soft power button under software or
* hardware control.
* Under software control the OS may control to when to allow to shut
* down the system. Under hardware control pressing the power button
* Under software control the OS may control to when to allow to shut
* down the system. Under hardware control pressing the power button
* 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)
{
@ -1254,6 +1257,22 @@ int pdc_soft_power_button(int sw_control)
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.
* Primarily a problem on T600 (which parisc-linux doesn't support) but

16
drivers/parisc/power.c
View File

@ -37,7 +37,6 @@
#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/notifier.h>
#include <linux/panic_notifier.h>
#include <linux/reboot.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
* executed any longer. This function then re-enables the
* soft-power switch and allows the user to switch off the system
/*
* parisc_panic_event() is called by the panic handler.
*
* 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,
unsigned long event, void *ptr)
{
/* re-enable the soft-power switch */
pdc_soft_power_button(0);
pdc_soft_power_button_panic(0);
return NOTIFY_DONE;
}